VASSCAA-9 - The 9th Vacuum and Surface Science Conference of Asia and Australia
SMC Centre
This biennial conference aims to bring together industry, education, development and research in vacuum science and technology within the Asian, Pacific and Indian Ocean regions. It is a conference of the vacuum societies of Australia, China, India, Iran, Japan, Korea, Pakistan, Philippines, and Taiwan. VASSCAA-9 is one of the main conferences supported by the International Union of Vacuum Science, Techniques and Application (IUVSTA).
The conference, which will run through National Science Week and the Sydney Science Festival, will introduce to the general public this enabling technology through a series of high-profile public events highlighting its importance to everyday life and future technologies and to the exciting science that drives its development.
Sponsors:
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Registration
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Opening
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Plenary: Lars Montelius
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Connected Science for Society: A Key Enabler for Disruptive Innovations 1h
Advances in Nanotechnology and Advanced Materials have played a profound role for the last few decades development of the modern society and it has paved the way for the present Digitalization age. Further developments in combination with AI, VR, Big data and Quantum Computation, will in the next decade be a major driver for disruptive innovations in various verticals as well as an effective tool for fostering the meaningful utilization of knowledge for a meaningful and sustainable global development.
The digital economy is transforming the science and innovation landscape allowing participatory rapid diffusion of knowledge, competencies and capabilities paving the way for effective and meaningful deployment of knowledge. The explosion of IoT-products, massive data and sharing economy services are mega-trends of today´s society and the immense interconnectivity change modern society in a pace never before being witnessed. These major societal developments challenge society. And these changes foster disruptive innovations. A key for such changes is the increased and participatory dialogue in society. This trend is clearly seen in the European funding policies becoming more aligned to mission driven perspectives.
Vacuum Science & Technologies have enabled the emergence of a number Key Enabling Technologies (KETs). These KETs will make solid contributions to the grand challenges of today, such as sufficient sustainable energy supply on demand, clean water to everyone, novel e-health solutions with impact on the growing ageing population multi-sickness panorama and life-styles diseases etc. Solutions to these challenges demands increased transversal interdisciplinary participation. Not only transversal within the Sciences but also transversal in all kind of societal dimensions including an increased empowered participation of people.
There is a need for an increased effort to effectively close the gap between societal needs and science & technology offers. The basics for science is curiosity - in the past mostly related to understand how things are related or how things work and nowadays more and more related to missions.
Finally, in order to fully tap all possibilities offered within the Key Enabling Technologies there is a continued need to put emphasis on transversal funding support schemes. If not, there is a risk that the enabling character of inventions will either disappear or take very long time to diffuse into other verticals, effectively hampering the innovation capital to be fully exploited.
Speaker: Prof. Lars Montelius (International Iberian Nanotechnology Laboratory )
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Plenary: Marcela Bilek
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Plasma processes that create one-step multi-functionalisable surfaces and nanoparticles: Fundamentals and applications 1h
Bio-functionalized surfaces are of great interest for a wide range of applications, particularly in biomedical diagnostics and implantable medical devices. We have shown that radicals embedded in polymeric surfaces facilitate simple, one-step surface-functionalisation [1]. The radicals are created by energetic ion bombardment of the surfaces. Covalent immobilisation of functional molecules is achieved by immersion or spotting / painting of the biomolecule-containing solutions onto the activated surfaces. This strategy simplifies covalent functionalisation of surfaces enormously, eliminating the need for wet-chemistry and the associated solvent disposal and yield problems. This approach has been used to immobilise bioactive peptides, antibodies, enzymes, single stranded DNA, and extra-cellular matrix proteins [2] onto many materials, including polymers, metals and ceramics.
This presentation will expound the fundamental science underpinning these new approaches. Process adaptions that extend the application of these techniques to functionalisation of the internal surfaces of complex, porous materials and structures will be explored. New applications enabling biological studies of the response of individual cells to proteins on a sub-cellular scale [3], and the preparation of multi-functionalisable nanoparticles for theranostics [4] will be elucidated.
Finally, we describe recent work which shows that spontaneous covalent immobilisation enabled by surface embedded radicals allows control of the density and orientation of surface-immobilised bioactive peptides [5]. This is achieved by tuning electric fields in the double layer at the surface during the immobilisation through pH variations and/or the application of external electric fields as delivered by a simple battery.
References:
[1] Bilek et al, PNAS 108:14405-14410 (2011);
[2] Bilek et al, Appl. Surf Sci 310:3-10 (2014);
[3] Kosobrodova et al, ACS Appl. Mater. and Interfaces (2018);
[4] Santos et al, ACS Appl. Nano Materials (2018);
[5] Martin et al, Nat. Comm. 9:357 (2018)Speaker: Prof. Marcela Bilek (School of Aerospace, Mechanical and Mechatronic Engineering & School of Physics, University of Sydney, NSW 2006, Australia)
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Morning Tea 30m
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Speaker Sessions and Seminars: IUVSTA - Highlight Seminars - 1
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X-ray photoelectron spectroscopy as a tool for control superlattice heterostructures quality and surface bilayer formation 20m
X-ray Photoelectron Spectroscopy (XPS) is probably the most widely used surface analysis technique. Using it, it is possible not only to determine the chemical composition of a given material, but also concentrations of all elements forming it. Additionally, XPS is very useful to ascertain the thickness of adlayer deposited on any kind of solid state substrate. The depth from which the information arise is typically not larger than 10 nm. This makes XPS especially suitable in nanotechnology applications.
In this talk it will be shown how, using XPS:
- a quality of superlattice heterostructures produced,
- progress of a surface bilayer formation (e.g. double layer of graphene on SiC surface or bilayer of Ga on GaN),
- thickness of the deposited adlayer when a surface bilayer is formed (e.g. during thermal treatment) on superlattice substrate,
can be determined.
The given formula can be easily extended to more complicated compounds which makes them very useful in practical applications.Speaker: Dr Leszek Markowski (Institute of Experimental Physics, University of Wroclaw, Poland)
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Speaker Sessions and Seminars: Magnetic surfaces, interfaces and nanostructures - 1
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Interface Engineering and Emergent Magnetism in Oxide Heterostructures 45m
Complex oxide interfaces have mesmerized the scientific community in the last decade due to the possibility of creating tunable novel multifunctionalities, which are possible owing to the strong interaction among charge, spin, orbital and structural degrees of freedom. Artificial interfacial modifications, which include defects, formal polarization, structural symmetry breaking and interlayer interaction, have led to novel properties in various complex oxide heterostructures. These emergent phenomena not only serve as a platform for investigating strong electronic correlations in low-dimensional systems, but also provide potentials for exploring next-generation electronic devices with high functionality. In particular, emergent magnetism at the oxide interfaces has profound application in future development of spintronic memory. In this talk, I will review our effort in exploring interface magnetism in various different systems. I will then focus on an heterostructure based on CaMnO_3/CaIrO_3 superlattices which is found to possess interface ferrimagnetism by charge transfer, perpendicular magnetic anisotropy up to room temperature, as well as Topological Hall Effect (THE) indicating the presence of magnetic Skyrmion. Emergence of Skyrmions in such symmetric, antiferromagnet/paramagnet superlattice is the first of its kind, and its stabilization is explained by an “interfacial roughness model”. The abrupt suppression of THE by large current allows measurement of threshold current density of ~10^8 A/m^2 and Skyrmion drift velocities. This system provides a novel route in stabilizing the Skyrmion phase in oxide heterostructure.
Speaker: Prof. A. Ariando (National University of Singapore)
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Speaker Sessions and Seminars: Thin Films - 1
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Scaling lab research to engage the manufacturing industry: a story of vacuum thin film coatings 45m
To remain competitive in a rapidly changing global market, many industries are looking at implementing new and innovative products. This sometimes requires engaging with scientific and engineering researchers to bring the latest discoveries to commercial products. The ultimate success of translating these discoveries into products will come from the ability to scale-up the fabrication processes from the lab into production.
This presentation will provide an overview of the collaborative projects between university researchers and industry. Specifically focused on the scale-up research being undertaken by the Future Industries Institute at UniSA in the area of thin film coatings. This research is aimed at scaling-up the thin film capabilities to create minimum viable product that can be tested by industry to meet the specifications set by their customers.
In one example, our on-going partnership with the Malaysia Automotive Institute (through the MAI-UniSA Automotive Innovation Centre) has seen the design, build and commissioning of a pilot production flow coating plus inline magnetron sputtering system to deposit multilayer thin film coatings on plastic substrates up to 600x600mm in size. This capability allows for prototype product of light weight plastic glazing for electric vehicles to be tested.
Such an approach to thin film materials research to manufacturing process design to partnered commercialisation of product with industry has in the past seen successful development of the world's first plastic automotive mirror. In partnership with SMR Automotive, the UniSA team's ability to scale-up lab based processes to bridge the gap towards commercial manufacture was critical. As a result over 3 million of these products have been manufactured and exported to the global automotive industry.
From this, the team have expanded their scale-up research to encompass thin film coating technology in the areas of defence, agriculture, renewable energy, and medical.
Speaker: Dr Drew Evans (University of South Australia)
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Lunch 1h
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Plenary: Chirs McConville
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Electron Accumulation at Semiconducting Surfaces 1h
The phenomenon of electron accumulation has been observed and identified at the surfaces of numerous semiconducting materials, including ZnO and InAs, and is in marked contrast to the electron depletion typically observed at the surfaces of conventional III-V, II-VI and Group IV semiconductor materials. However, with the advent of high-quality epitaxially grown materials, a more general model of surface electron accumulation has been developed – particularly following the discovery of this phenomenon at the surfaces of the Group-III nitride material, indium nitride (InN). More recently still, electron accumulation has been observed at the surfaces of a particular sub-set of epitaxial oxide semiconductor materials, that display both optical transparency and a high degree of electrical conductivity, the so-called transparent conducting oxides (TCOs). In this presentation examples from the surface and bulk electronic properties of InN, In-rich InGaN, and several epitaxially grown oxide semiconductors, including In2O3, CdO and ZnO, will be discussed along with the effects of modifying their surfaces by controlled adsorption. The valence band density of states and the surface electronic properties of these materials have been studied using high-resolution synchrotron radiation angle-resolved photoemission (SR-ARPES) and core-level photoemission spectroscopy with hard x-rays (HAXPES), and these data are compared with theoretical DFT band structure calculations. The origins of the phenomenon of surface electron accumulation and the quantized nature of the surface 2D electron gas, will be discussed in terms of the band structure and intrinsic properties of these materials.
Speaker: Prof. Chris McConville (RMIT University)
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Break 15m
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Speaker Sessions and Seminars: IUVSTA - Highlight Seminars - 2
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Quantum-Based Pascal and The End of Mercury Manometers 30m
New methods of pressure and vacuum realization that are based on quantum calculations are currently under development. This is exciting in that it fits with the current SI-redefinition paradigm, that if a new technique relies upon a quantum property, measurement, calculation, or invariant of nature, then this technique can have served as a primary standard. Standards built this way are then directly tractable to the SI and will not itself require re-calibration. For the Pascal, a Fixed Length Optical Cavity (FLOC) and methods the enable the FLOC to be primary, including a Variable Length Optical Cavity (VLOC) will be discussed. These new methods operate by measuring the gas pressure though the interaction of light with the atomic or molecular properties of the gas and have enabled a new quantum-based pressure standard. Development of these new standards will enable the elimination of mercury manometers, a standard that has been in use for four centuries. The talk will cover the current status of the effort by National Metrology Institutes to re-define standards through the use of quantum based measurements, and will connect current NIST this efforts to the coming SI-Redefinition. The talk will also briefly update activates to develop a Cold Atom Vacuum Standard (CAVS) which will enable a quantum-based vacuum standard capable of measuring extreme vacuum (XHV). Evangelista Torricelli invented the mercury in 1643, and while he did not realize it at the time, started a new field of vacuum technology which lead to the explosion of technology that lead to the modern national vacuum societies of today!
Speaker: Dr Jay Hendricks (NIST)
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Speaker Sessions and Seminars: Magnetic surfaces, interfaces and nanostructures - 2
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Neutron scattering techniques for understanding restricted dimensionality in magnetism: interfaces, surfaces and more! 30m
In this invited talk I wish to give an overview of neutron scattering at ANSTO. From this we will see neutron scattering as a powerful tool for understanding the structure and dynamics of materials. There are many different types of instruments utilizing neutrons from the OPAL reactor at ANSTO and these will be introduced in some detail. In particular I wish to focus on recent scientific results from magnetic materials such as BiFeO3 [1] and linarite [2] and give examples of the information that neutron scattering has revealed. By applying this technique to the study of restricted dimensions, we can devise better ways to develop new materials for future technologies.
[1] Joel Bertinshaw et al., Nature Communications 7, 12664 (2016)
[2] K.C. Rule et al., Physical Review B 95, 024430 (2017)Speaker: Kirrily Rule (ANSTO)
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Speaker Sessions and Seminars: Thin Films - 2
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Quinary indium gallium zinc aluminum oxide films and thin-film transistors 30m
Recently, thin-film transistors (TFTs) used as switching and driving devices have been widely applied in liquid-crystal displays (LCDs), flexible electronics, smart cards, etc. Several transparent conducting oxide (TCO) films are being investigated to obtain channel layers, owing to their wider energy bandgap and lack of absorption of visible light. In view of their wider energy bandgap, higher transmittance, and reasonably high electron mobility, quaternary indium gallium zinc oxide (IGZO) films have been widely used as the channel layer of TFTs in displays with larger frame size and high pixel resolution. However, IGZO TFTs still face the problem of long-term instability induced by oxygen vacancies in IGZO film. In the previously reports, Al has been incorporated into ZnO-based films to stabilize oxygen and improve their stability, because of its higher bonding energy with oxygen. Consequently, the stability of oxygen in the quinary indium gallium zinc aluminum oxide (IGZAO) films could be improved by the Al-O bonds. Furthermore, the 3s orbital of Al cation can provide an extra transport pathway and widen the conduction-band bottom to increase the electron mobility. In this work, high-quality and highly stable IGZAO films were deposited using vapor cooling condensation method to form the channel layer of highly stable TFTs.
To investigate the effect of Al, both IGZO and IGZAO films were deposited on sapphire substrates by vapor cooling condensation system. In the system, Al metal and IGZO powder were loaded into respective tungsten boats. During deposition, sublimated IGZO vapor was condensed and deposited on sapphire substrate attached to a stainless-steel holder with liquid nitrogen cooling system. Besides, IGZAO films were deposited from IGZO powder heated at 1033oC and Al metal heated at 1254oC, simultaneously. The channel width (W) and the channel length (L) of the resulting TFTs were 100 um and 10 um, respectively.
It was found that the electron mobility and electron concentration of the IGZAO films were 7.2 cm2/V-s and 9.94E15 cm-3, respectively. The maximum iDS of the IGZO and IGZAO TFTs when operated at gate–source voltage (vGS) of 5 V was 12.1 uA and 20.8 uA, respectively. Compared with the gm of 3.73E-6 S for the IGZO TFTs, the IGZAO TFTs exhibited a better gm of 7.63E-6 S. Consequently, the corresponding field-effect mobility uFE of 23.3 cm2/V-s of the IGZAO TFTs was better than that of 11.3 cm2/V-s of the IGZO TFTs. Compared with the S value of 223 mV/dec of the IGZO TFTs, the S value of the IGZAO TFTs was improved to 168 mV/dec. The threshold voltage of the IGZO and IGZAO TFTs changed by 0.51 V and 0.34 V, respectively, as the temperature was changed from 225 K to 300 K.
This work was supported from the Ministry of Science and Technology of the Republic of China under contract No. MOST 105-2221-E-006-171-MY3.Speaker: Prof. Ching-Ting Lee (Yuan Ze University)
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Afternoon Tea 30m
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Speaker Sessions and Seminars: IUVSTA - Highlight Seminars - 3
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Low-pressure/environmental electron and photoelectron techniques; a new age for a merged biointerface analysis. 30m
Surface and interface bio-analytical systems can be categorized, as well as surface modification and biofunctionalization processes, into wet and gas phase (mostly vacuum) operating techniques. While wet and gas phase biofunctionalization routes have coexisted and are even used in sequential processes, the use of traditional vacuum analytical techniques has been severely criticized due to modification of natural thermodynamic conditions and potential sample damage. This has not fully excluded the use of electron microscopies (EMs) and photoelectron spectroscopy (XPS) in the analysis of biointerfaces, but has created controversies by comparison with information provided by wet analytical processes. That is the reason why, many biointerface analysis studies using mechanical, electrochemical or optical transduction of biomolecular sorption do not provide additional EM or XPS evidence of the interface. The advantage of some of these techniques (such as the Quartz crystal microbalance or surface plasmon resonance) is the possibility to monitor the kinetics of modification of the biointerface. Nevertheless, these techniques monitor exclusively the addition of new matter (as added mass or added index of refraction) and leave a margin of uncertainty (depending on the considered protocol) on the matter actually adsorbed on the surface. New technological advances, mainly electron selective pinholes enabling pressure gradients, have allowed the development of so called environmental electron microscopies (envEM) and environmental photoelectron spectroscopies (envXPS). These new advancements demonstrate that, even if analyses do not take place at atmospheric conditions, the analyzed biological samples keep a hydration layer as the most significant physicochemical trace of their pristine state upon analysis. The control of thermodynamic conditions in envEMs (particular case of a wet scanning transmission EM) allows for instance a recording of water adsorption isotherms from the contrast change induced by a water adsorption progressing at increasing relative humidity. In the case of envXPS, the presence of a water layer is evidenced by a trace component in the O1s core level, assigned to water in the vapor phase. From these seeding fundamental results, we provide several examples of how envEMs and envXPS have already complemented applied biointerface structures in the therapeutic and diagnostics field. These studies suggest that the gap to make compatible the results of the analysis of biointerfaces by wet and vacuum techniques is shortening and may open a new age for a fully merged biointerface analysis.
Speaker: Dr Manso Silvan Miguel (Universidad Autónoma de Madrid) -
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Recent highlights in plasma science and applications 30m
Plasmas underpin many existing technologies and drive next-generation innovations. Non-equilibrium plasmas are a powerful medium for ionisation, excitation, dissociation, and bond modification, at solid surfaces, in liquids and gases. These processes produce an intriguing reactive environment, combining ions, electrons, reactive neutrals and photons. Atom-scale precision can be achieved for etching and deposition profiles enabling advanced manufacturing techniques for a variety of applications from electronic chip manufacturing to solar cell production. Modern trends have seen the advent of plasma medicine applications for cancer treatment and wound healing; micro-chemical reactors can convert waste products or ambient feedstocks into valuable chemicals, or energy storage media for clean energy and agricultural applications. Key to developing these applications for plasma control and understanding the underlying processes are advancing diagnostic and simulation techniques.
Speaker: Dr Deborah O'Connell (University of York) -
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Recent Advances in Surface Engineering 30m
Surface Engineering (SE) is the science and technology of improving the surface properties of materials for protection in demanding contact conditions and aggressive environments. SE also encompasses engineering new multi-functional surface properties, such as electrical, optical, thermal, chemical, and biochemical properties. It involves multiple or hybrid processes which include substrate modification and deposition of overlayers in complex architectures. These processes enhance adhesion and optimize composition or microstructure to enhance protective properties coupled with other functionality. The substrates may be of complex shapes, like metal-cutting tools and automotive or aerospace components, and range in size from micrometers, such as in MEMS or NEMS (micro- or nano-electromechanical systems) devices, to meters, such as in architectural glass. The applications are wide-ranging, and include, for example, control of friction, wear-resistance, corrosion-resistance, thermal-barrier coatings, decorative coatings, bioimplants, antimicrobial layers, web-coatings, and thin films with engineered electrical and optical responses. Areas of scientific interest range from first-principle atomistic studies of new materials, which are both hard and ductile, (i.e., tough), to scientific and technological advances in synthesis methods, structural and chemical characterization techniques, property measurements, and performance characterization of surface-engineered parts. I will highlight a few selected SE advances from the past three years.
Speaker: Prof. Ivan petrov (University of Illinois) -
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Highlights of the IUVSTA Thin Film Division 2018 20m
Science and technology of thin films is in continuous progress. Interesting technological approaches and initiatives for accelerated materials discovery using machine learning are under development to meet the current trends of automation and data exchange in manufacturing technologies within what is called Industry 4.0 that involves cyber-physical systems, the Internet of things, or cognitive computing. In this context, it is of paramount importance not only the development of new materials with new or improved properties, but also the search of new smart sensors and self-reporting materials able to “communicate” in service general changes in their environment or even, report on possible damage/degradation by means of the variation of their chemical or structural properties. In this presentation, we will review few selected papers that focus on either fundamental aspects related to the control of thin film growth or to their innovative application as functional coatings to meet these challenges. Thus, it will be reported how the presence of residual gases during magnetron sputtering thin film growth can be used to control the microstructure of the deposits [1] of importance in industrial implementation, a clever way to study elemental diffusion in bimetallic systems [2], or the conditions to grow vertically aligned columnar nanocomposite thin films [3]. Other topics that will be addressed are the fabrication of thin films by agglomeration of nanoparticles [4] to control wetting properties of these films, or the identification of ultrathin magnetic structures [5]. On the other hand, several examples of functional coatings, such as the performance of transition metal dichalcogenides/ferroelectric systems as resistive switching for resistive random access memories [6], colorimetric energy sensitive scintillators based on luminescent multilayer designs or microfluidic liquid sensors based on porous films [7]
[1] F. G. Cougnon et al. Appl. Phys. Lett. 112, 221903 (2018).
[2] V. Takats et al. Appl. Surf. Sci. 440, 275 (2018).
[3] Y. Wang et al. Sci. Reports 7, 11122 (2017).
[4] A. Shelemin et al. J. Phys. D: Appl. Phys. 49, 254001 (2016).
[5] S. Ruiz-Gomez et al. Nanoscale 10, 5566 (2018).
[6] J.P.B. Silva et al. J. Mat. Chem. C 5, 10353 (2017).
[7] J. Gil-Rostra et al. ACS Appl. Mater. Interfaces 9, 16313 (2017). M. Oliva-Ramírez et al. Sens. Actuators B 256, 590 (2018).Speaker: Francisco Yubero (ICMS (CSIC, Univ. Seville)) -
17:20
Nanoscience as a discipline and its impact on modern society 20m
IUVSTA Nanometer Structures Division Highlights
Nanoscience as a discipline and its impact on modern society
Corresponding author: Ana G. Silva, acs@fct.unl.pt
In the highlight seminar of scientific Nanometer Structures Division (NSD) of IUVSTA we provide an overview of some recent developments in nanoscience and how its applications comprise a vital contribution to social well-being, contributing to a sustainable economy. Nanoscience impacts on a variety of technologies such as energy, nano-electronics, communication, health, smart cities and the environment. Examples are given in a range of areas. New materials have mushroomed since development of nanomaterials – here we novel synthetic techniques, such as preparation of core-shell nanoparticles which are used to tune photocatalytic activity; formation of nano-columnar Ti displaying both antibacterial and black metal material properties; preparation of chalcopyrite nanowires, which can be applied in photovoltaics with high conversion efficiency’; growth of PdO-coated WO3 nano-needles showing extreme sensitivity and selectivity to hydrogen, and finally use of laser ablation to form nanoparticles, nanowires, and nanostructured materials. Nano-tools are also opening new opportunities. We present a reproducible method for depositing 1-2 nm passivation layers, with atomically sharp interfaces, for SiC nano-electronics devices. We present in addition, the use of atomic force microscopy to investigate enhancement of oil recovery in reservoirs, as well as to investigate wetting properties of unique WS2 nanotubes to elucidate their incorporation in biopolymers. Additional examples include controlled manipulation of single molecules by the AFM tip, a video-rate AFM to examine dynamics of biological systems, and controlled manipulation of organic semiconductor crystallites on 2D materials by the atomic force microscopy (AFM) tip. The seminar will include recent and significant achievements of the members of the Nanometer structures scientific division and their colleagues.
Acknowledgments
Ana G. Silva, Chair of the Nanometer Structures Division (NSD) of IUVSTA, acknowledges Lars Montelius, President of IUVSTA, for his most valuable support by presenting the seminar on NSD behalf.
Ana G. Silva acknowledges, Christian Teichert and Sidney Cohen, respectively vice-chair and scientific secretary of NSD division for their exceptional support. In addition, Ana G. Silva acknowledge the contributions of the members of the division and their colleagues who kindly share their most recent research developments. The highlights seminar includes contributions from Nancy A. Burnham, Carla Bittencourt, José Garcia-Martin, Yves Huttel, Nikolay Nedyalkov, Sasha Sadewasser, Takayuki Uchihashi, Christian Teichert, Sidney Cohen and Ana G. Silva.Speaker: Prof. Lars Montelius (International Iberian Nanotechnology Laboratory ) -
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Oxide based electronics for neuromorphic computing 20m
In thin film form, transition metal oxides can be subjected to intense electric fields and are known to exhibit characteristic resistance changes that are of increasing interest for a new generation of low power oxide-electronics, including: resistive random access memory (ReRAM) as a replacement for non-volatile flash memory, field-programmable gate arrays (FPGAs) for reconfigurable electronics, and artificial synapses and neurons for neuromorphic computing. The neuromorphic computing application is particularly interesting as it provides the basis for a compact, low-power neural network capable of repetitive learning tasks, such as image recognition, signal processing or autonomous navigation. Like their biological counterparts, these networks are based on the large scale integration of synapses and neurons, where the former control the amplitude of propagating signals and the latter respond to the relative strengths and timing of these signals.
This presentation introduces a new class of solid-state synapses and neurons based on non-volatile resistive-switching and volatile threshold-switching in oxide thin films, respectively. The physical processes underpinning these devices are discussed and examples of device operation are used to highlight their capabilities and limitations.
Speaker: Prof. Elliman Robert (Australian National University)
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Speaker Sessions and Seminars: Magnetic surfaces, interfaces and nanostructures - 3
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Octahedral Engineering and Interfacial Structure of Heteroepitaxial Complex Oxides 30m
Epitaxial strain, utilizing the lattice-mismatch between heterogeneous systems, has been generalized as a standard tool to improve or induce unconventional physical and materials properties, such as ferroelectricity and ferromagnetism. The fact it is so successful that it overwhelmingly enveils another important concomitant parameter, the symmetry-mismatch, that naturally occurs at the interface. The latter can be significant based on early theoretical predications, but direct evidence still lacks due to the challenging needs of 1.) characterization techniques, and 2) an appropriate method to separate it from lattice-mismatch. Here we provide experimental evidence that the symmetry-mismatch strongly impact the magnetic and electronic functionalities of complex oxides using epitaxial Cobaltite and Titanate as examples, e.g. suppressing the TiO6 octahedral tilts in CaTiO3 can drive it into ferroelectric phase and distortion in CoO6 can induce long range ferromagnetic ordering in thin-film LaCoO3, which is paramagnetic in bulk case. It is also suggested that octahedral engineering may work as a useful tool to tune the functionalities in complex oxide heterostructures.
Speaker: Prof. Liang Qiao (University of Electronic Science and Technology of China) -
16:00
Manipulating the electronic structure and magnetism of spin-orbit Mott insulator by tailoring superlattices 30m
In this talk, we will introduce how to fabricate and study the artificial 5d iridate superlattices by the combo of oxide molecular beam epitaxy (OMBE), in-situ angle-resolved photoemission spectroscopy (ARPES) and X-ray magnetic circular dichroism (XMCD) techniques.
We successfully fabricated a series of [(SrIrO3)$_m$/(SrTiO$_3$)]$_n$/SrTiO$_3$(100) superlattices using the layer-by-layer OMBE. The high crystalline quality has been confirmed by both Atomically resolved HAADF-STEM and X-ray diffraction measurements. In this series of superlattices, the metal-insulator transition (MIT) is introduced by tuning the thickness of SrIrO$_3$ interlayer. Besides, the emergent interfacial magnetism by such an artificial dimensionality control of iridates is realized.
The mechanism of this MIT and the elemental specificity of magnetism have been then investigated by the in-situ ARPES system and the XMCD, respectively. Our results could provide a comprehensive understanding of the phase transition in this spin-orbit Mott insulator.Speaker: Prof. Dawei Shen (SIMT, CAS) -
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Confinement-Induced Giant Spin-Orbital-Coupled Magnetic Moment of Co Nanoclusters in TiO2 Films 30m
High magnetization materials are strongly required for the fabrication of advanced multifunctional magnetic materials and devices, whereas, the development of high magnetization materials is extremely slow. In this work, we propose a new strategy to achieve high magnetization above room temperature by nanoengineering. In detail, 5% Co-TiO2 film has been deposited using pulsed laser deposition. By delicately controlling deposition parameters, Co clusters are formed and further confirmed by transmission electron microscopy, energy dispersive spectroscopy and X-ray absorption near edge spectroscopy. The film exhibits a very high saturation magnetization measured by magnetometer, equivalent to 6.54 B/Co, given that the magnetic moment is all contributed from Co dopant. However, X-ray magnetic circular dichroism indicates that Co only has a magnetic moment of 3.5 B. The rest of the moments are contributed from Ti and O. First principles calculations demonstrate that metallic Co nanoclusters embedded in TiO2 matrix can have large both spin and orbital moments, consistent with experimental results. The work indicates that very small nanoclusters under confinement environment can exhibit very large magnetic moments above room temperature, which is promising for designing artificial high magnetization materials.
Speaker: Prof. Jiabao Yi (University of Newcastle) -
17:00
Neutron studies of iron-based superconductors 15m
The study of magnetic structure and neutron scattering on potassium intercalated iron selenide (K2Fe4Se5) and its doped system (K1.9Fe4+x-yAySe5, A=Cu/Mn) is presented here. An intriguing phenomena is observed in the magnetic properties due to doping, which could provide different view to the mechanism of superconductivity. Excess iron in the Fe-chalcogenide family, appears to somehow induce Fe-vacancies from an ordered to a disordered state which may be the origin of superconductivity. In this study, extra iron dopants induce superconductivity in the parent compound, K2Fe4Se5, while extra manganese and copper doping suppresses superconducting behavior. The long range magnetic ordering temperature (TN) is confirmed to be lower than the Fe-vacancy order-to-disorder temperature (TVO). Anisotropic transport properties are shown to exist in K2Fe4Se5 [1]: the interlayer properties playing an important role in superconductivity. Manganese and copper substitution of iron sites, however, induce the shift of the superconducting critical temperature and the suppression of superconductivity due to the change in competition between anti-ferromagnetism and superconductivity in this 245 system [2-3].
Reference
[1] Y. J. Song, Z. Wang, Z.W. Wang, H. L. Shi, Z. Chen, H. F. Tian, G. F. Chen, H. X. Yang and J. Q. Li, European Physics Letter, 95, 37007 (2011)
[2] Tzu-Wen Huang, Ta-Kun Chen, Kuo-Wei Yeh, Chung-Ting Ke, Chi Liang Chen, Yi-Lin Huang, Fong-Chi Hsu, Maw-Kuen Wu, Phillip M. Wu, Maxim Avdeev, and Andrew J. Studer, Physical Review B 82, 104502 (2010)
[3] Dian Tan, Changjin Zhang, Chuanying Xi, Langsheng Ling, Lei Zhang, Wei Tong, Yi Yu, Guolin Feng, Hongyan Yu, Li Pi, Zhaorong Yang, Shun Tan, and Yuheng Zhang, Physical Review B 84, 014502 (2011)Speaker: Ms Jie-Yu (Shirley) Yang (Institute of Physics, Academia Sinica, Taipei, Taiwan) -
17:15
Hidden complex magnetic interaction at La0.67Sr0.33O3/SrTiO3:Nb (111) interface 15m
One of the major goals in condensed matter physics is to search for materials with multifunctionality at the quantum level. Strongly correlated oxides seem to be one of the most attractive candidates due to the collective behaviors emerged from strong interactions and correlations among their degrees of freedoms. Incorporating strongly correlated oxides into epitaxial heterostructures expands the space of new phenomena possible due to dimensional confinement and interfacial coupling. La0.67Sr0.33MnO3 (LSMO) is a key example of a strongly correlated perovskite oxide material in which a subtle balance of competing interactions gives rise to a ferromagnetic metallic ground state. This balance, however, can be easily tuned at interfaces. By constructing a strong polar interface between [111]-oriented LSMO and SrTiO3:Nb, the electronic and structural symmetry mismatch leads to lattice and charge modification which changes the magnetic interaction at the interface. An antiferromagnetic interaction stabilized at the interface results in spontaneous magnetic moment reversal and inverted hysteresis effects, which demonstrate that intimate competition in electronic, spin and lattice degrees of freedom in transition metal oxides can lead to new functionality.
Speaker: Dr Meng Meng (Institute of Physics, Chinese Academy of Sciences)
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Speaker Sessions and Seminars: Thin Films - 3
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Key Materials Issues in Co-Sputtered Aluminium-Gallium Oxide Films and Their Applications to Solar-Blind Photodetectors 30m
A wider bandgap material possesses great merit as it allows the design of devices such as high sensitive wavelength-tunable photodetectors (PDs). Aluminum element is a candidate to enlarge the bandgap of Ga2O3 since Al2O3 has a larger bandgap. The similar electron structures of Al and Ga makes the (AlGa)2O3 alloy possible to achieve. Therefore, by incorporating Al2O3 into Ga2O3, the bandgap of aluminum-gallium oxide (AGO) materials can be modulated toward a higher value (commonly 5~7 eV), which expands its deep ultraviolet (DUV) applications. In this study, the wide-bandgap AGO thin films were grown on sapphire by co-sputtering of Al and GaO targets, which were used DC and RF powers, respectively. The RF power for the GaO target was fixed at 100 W. Various DC powers of 5, 10, 30, 50, and 70 W were employed for the Al target. The substrate temperature and AGO thickness were kept at 600 C and 120 nm, respectively. Moreover, the pure Ar and O2 gases were introduced into the growth chamber at a constant [O2/(Ar + O2)] partial pressure of 16%, and the working pressure was fixed at 5 mTorr. Additionally, the as-deposited AGO films were annealed at 900 C for 20 min in air. The AGO films deposited at the Al sputtering power of 5-50W presented single crystalline phase with AGO(-201)-family diffraction peaks. However, as the Al sputtering power was increased to 70 W, the AGO film was amorphous. In addition, the energy gap (Eg) values can be obtained via their transmittance spectra. As the Al sputtering powers were 5, 10, 30, 50, and 70 W, the Eg values of AGO films were determined to be 5.06, 5.10, 5.13, 5.19, and 5.24 eV, respectively. Furthermore, the AGO films grown at the Al sputtering power of 5-30 W were selected to prepare the metal-semiconductor-metal PDs. As a 20-V bias was applied, the device fabricated with AGO film using the Al sputtering power of 10 W has better performance, where its dark current and responsivity are 1.8 × 10−12 A and 0.37 A/W, respectively. By adjusting the growth conditions of AGO films, the performance of PDs will be improved and presented in this work.
Speaker: Prof. Dong-Sing Wuu (Department of Materials Science and Engineering, National Chung Hsing University) -
16:00
A Hybrid Hydrogen Storage System Based on Hollow Glass Microspheres 30m
The theoretical and experimental aspects of a hybrid hydrogen storage system consisting of hydrogen pressurized hollow glass microspheres (HGMS) and a hydride, e.g. NaBH4, will be discussed. Volumetric and gravimetric storage densities are assessed. Thermal aspects and hydrogen diffusion through glass are discussed. It is shown that hydrogen pressurized HGMS in combination with a hydride bear the potential to achieve storage densities up to 30-50 kg/m³. Hydrogen is stored by heating and pressurizing the spheres at approx. 85 MPa, forcing the gas into the spheres. Hydrogen is released by heating again to approx. 250°C. To reach this temperature the exothermal chemical reaction of NaBH4 with water, which produces hydrogen as a welcome by-product, is used. To promote the reaction the HGMS (diameter approx. 20 µm) have to be coated with a catalyst.
To produce the catalyst coating on the HGMS a special coating device based on non-reactive (for metals) and reactive (for non-metals) magnetron sputtering was designed. It provides continuous intermixing of the fragile spheres in a container by a combination of rotation and concussion. In the final design stage the coating mechanism can handle one liter of microspheres. The catalytic reaction is tested in a set-up which measures the released heat and amount of hydrogen. For Ru deposited on an adhesion promoting film of TiO2 the theoretical maxima of released heat and hydrogen could be achieved, thus rendering even the hydride based part of the system alone an interesting option for hydrogen storage.Speaker: Dr Christoph Eisenmenger-Sittner (Vienna University of Technology) -
16:30
Surface hardness of flexible carbon fiber sheets enhanced by deposition of organosilicon oxynitride thin films with an atmospheric pressure plasma jet 15m
The transparent polymers reinforced by carbon fiber cloth, so-called flexible carbon fiber sheets (FCFS), are frequently exploited due to several advantages such as low specific weight, low cost and ease of processing. However, the soft surfaces of FCFS restrain their usage. The constrains of soft surfaces for FCFS can be resolved by deposition of hard transparent protective thin films, such as SiO2 and Al2O3 onto the surfaces of transparent polymers. An enhancement on surface hardness of FCFS) substrates by deposition of organosilicon oxynitride (SiOxCyNz) with an atmospheric pressure plasma jet (APPJ) by mixing the tetramethyldisiloxan (TMDSO) vapors with O2 gases, injecting into air plasma jet and sprayed onto FCFS substrates at room temperature (~23℃) and an atmospheric pressure is investigated. Surface hardness of the FCFS substrate is improved form 2B for as-received FCFS substrate to 8H for FCFS/APPJ-synthesized SiOxCyNz while tested by the pencil test method (ASTM3363). The nanograins, and the chemical bonds Si-(O)4 and (R)-Si-(O)3 produced in APPJ-synthesized SiOxCyNz thin films results in a high surface hardness of up to 8H against the pencil 8H scratched under a loading of 765 g at an angle of 45o.
Speaker: Prof. Yung-Sen Lin (Department of Chemical Engineering, Feng Chia University) -
16:45
Determining the effect of substrate cleaning on the solution stability of plasma polymer films 15m
Plasma polymerization modifies surfaces via the deposition of a thin film possessing specific functional groups. The organic monomer is introduced into the low pressure chamber as a vapour, fragmented via radio frequency and deposited onto all surfaces in contact with the plasma. Commonly used monomers such as octadiene, allylamine and acrylic acid enable the deposition of hydrocarbon, amine and carboxylic acid terminated surfaces respectively. Surface cleaning prior to the deposition of thin films is frequently carried out to improve film adhesion. The use of plasma polymer films in biomedical applications has increased the demand for coatings suitable for use in physiological conditions. Significant changes in film properties in aqueous conditions have serious implications on the incorporation of these films in biomedical technologies and devices.
In this study, silicon wafer substrates were cleaned by several different methods prior to the deposition of plasma polymerized thin films to investigate the influence of substrate cleaning on film stability in aqueous solutions. The substrates were used untreated or cleaned by liquid sonication, UV/ozone cleaning or air plasma. X-ray photoelectron spectroscopy (XPS) and contact angle measurements were undertaken to determine the effect of the cleaning method on surface chemistry and wettability. After cleaning, the substrates were coated by plasma polymerized octadience, acrylic acid or allylamine thin films. The surface chemistries and film thicknesses of the plasma polymerised films were determined by XPS and variable angle spectroscopy ellipsometry respectively. The plasma polymerised films were immersed in both Milli-Q water and phosphate buffered saline for time periods of 1, 24 and 168 hours. Films were again analysed via XPS and ellipsometry to determine the influence of substrate cleaning, immersion solution and immersion duration on film stability. Substrate cleaning was shown to have an influence on film stability with visible pitting on some films, even after only 1 hour of immersion. Substrate cleaning is an important step prior to the deposition of thin films and can be used to extend the solution stability of plasma polymerised films, which has important implications for a variety of biomedical applications.
Speaker: Dr Karyn Jarvis (Swinburne University of Technology) -
17:00
Reactive sputter deposition of transparent and low refractive-index MgF2 thin films using a double-grid negative-ion retarding electrode 15m
MgF$_{2}$ thin films deposited by magnetron sputtering show optical absorption in the visible range because of the formation of F defects or Mg clusters by the incidence of energetic F- ions to substrate [1,2]. In addition, deposition rate of sputter deposited MgF$_{2}$ thin film is less than a few nm/s [1, 2], which is regarded as rather low compared to that of other compound thin films. In this study, effectiveness of negative bias voltage applied to a double-grid electrode set between the cathode and the substrate on increase in film deposition rate and suppression of optical adsorption has been examined in MgF$_{2}$ reactive sputter deposition using Ar-CF$_{4}$ mixture as discharge gas.
The sputtering apparatus used in the experiments was a batch-type system with the cathode of a Mg plate (76.2 mm dia., 99.99 % in purity). The distance between the target and the substrate was 51 mm. A double-grid electrode with 120 mm by 120 mm squared was set between the target and the substrate. The distance from the grounded grid to the target and between the two grids were 15 and 6 mm, respectively. The grid adjacent to the target was grounded and the other was biased. The pressure of discharge gas of Ar+CF$_{4}$ was kept at 0.8 Pa. The flow rates of Ar and CF$_{4}$ were 2.5 sccm, respectively. The cathode was driven by dc power supply (AE MDX 1.5K). The cathode power ranged 100-108 W for a constant discharge current of 0.3 A. The retarding voltage was changed from 0 to -500 V. Borosilicate glass plates (80 × 80 × 0.9 mm$^{3}$) were used as substrate. Thickness of thin films was measured by using a stylus profiler. Optical transmittance and reflectance were measured by a double-beam spectrophotometer.
The change in the retarding voltage affected both the film deposition rate and optical absorption. The MgF$_{2}$ thin film deposited without applying a retarding voltage to the driven grid showed the multiple-ring-shaped area with ptical absorption. By applying a retarding voltage of -50 V, the ring-shape was disappeared and transparent MgF$_{2}$ thin films were deposited. The optical absorption coefficient of thin films was reduced to <2×10$^{-4}$ nm$^{-1}$ in the visible range and the refractive index was <1.40. The film deposition rate was increased to >10 nm/min from < 1nm/min by applying a retarding voltage of -30 to -500 V. In addition, the film thickness uniformity distribution in the substrate was drastically improved due to the increase of the deposition rate in the area facing to the target erosion.
[1] L. Martinů, et al., Thin films prepared by sputtering MgF$_{2}$ in an rf planar magnetron, Vacuum 35 (1985) 531.
[2] K.Iwahori, et al., Optical properties of fluoride thin films deposited by RF magnetron sputtering, Appl. Opt. 45 (2006) 4598 -4602.Speaker: Prof. Eiji Kusano (Kanazawa Institute of Technology) -
17:15
Evaluation of Graded Composite Film Morphology 15m
The paper presents an efficient tool to research morphological properties of various composite structures. It focuses on the composites that are created by metal particles in a dielectric matrix. Nevertheless, the results could be used for other similar two-phase systems. The particles are assumed to be more or less randomly distributed in the matrix, and a low metal volume fraction is supposed. The hard-sphere model for generation of the composite structures is described. The Voronoi tessellation was chosen as a very efficient method of mathematical morphology. It is able to describe three-dimensional composite structure morphology simply using one two-dimensional section in the given structure. To evaluate the degree of disorder of the structure, a novel scalar measure is introduced. Results for homogeneous and graded composites are presented. It is shown that the scalar measure gives the possibility to precisely evaluate the degree of disorder of the composite structures. The sensitivity of the method is very good and its noise is low. It is independent of the section chosen.
Speaker: Prof. Stanislav Novak (Faculty of Science, J. E. Purkinje University) -
17:30
Dependence of Thermal Conductivity of MPCVD Diamond Thin Films on Oxygen Concentration 15m
There are various applications for which diamond thin films (DTFs) have gained attention due to their unique physical properties including good optical properties, high thermal conductivity, high electrical conductivity etc. The most prominent among all is the high thermal conductivity of diamond which makes it a potential candidate for heat spreading and other such applications in the field of electronics. To date, various methods have been introduced to enhance the above mentioned properties of the diamond thin films which typically involve doping, and variation in process parameters. In presented study, a series of DTF samples was prepared at 750°C with different oxygen concentrations. Microwave plasma chemical vapour deposition (MPCVD) method was used for sample preparation at different process parameters (H2 flowrate (99 sccm), CH4 flowrate (1 sccm), Power (600W), Gas pressure (20 Torr), substrate temperature (750°C), deposition time (24 hours)), which were kept constant during film deposition. The effect of variation in oxygen concentration on structural, morphological, and thermal transport properties of diamond have been studied. For structural analysis of the prepared samples, Raman spectroscopy was used which confirmed the formation of good quality DTFs. The addition of oxygen to the growth enhanced the crystallinity and morphology of the samples which was revealed by scanning electron microscopy (SEM). Moreover, morphological analysis showed that the growth of the (100) facet was enhanced for DTFs prepared at low oxygen concentration. Sample thermal conductivity was also analysed by utilizing Raman thermography and these results were correlated against growth conditions. It was found that, the structural features, morphology and thermal conductivity of the samples were correlated with each other.
Speaker: Ms Fatima Tuz Zahra (Macquarie University, NSW 2109, Australia)
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Poster Session - Main Hall Tuesday
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Poster Session Themes 2h
- Applied Surface Science
- Plasma Science & Technology
- Biosurfaces, interfaces, nanostructures
- Surface Engineering
- Nanometer Scale Science & Technology
- Renewable Energy Technologies
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Registration
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Plenary: Gordon Wallace
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Graphene – Cellular Interactions and Implications for Medical Device Technologies 1h
Graphene is an extraordinary material with a combination of properties including electrical conductivity, exceptional strength and biocompatibility that makes it attractive in a number of areas of application.
Careful control of all steps from sourcing the graphite, to exfoliation and chemical modification of graphene sheets, is important in rendering the dispersions obtained amenable to subsequent fabrication such as spray coating, printing or fiber spinning.
Recent advances in our laboratories have involved the development of chemistries that retain the inherent properties of graphene while rendering it processable in aqueous or organic solvents.
Chemistries developed here have also enabled effective formation of graphene containing composites that are amenable to fabrication.
Success in these areas has led to the application of graphene and structures containing it, for energy storage and conversion, as well as in biomedical areas including neuronal recording and stimulation electrodes, as well as scaffolds for bone regeneration.
As part of this presentation a critical non-technical requirement will be discussed: the need for a collaborative interdisciplinary approach to ensure effective and efficient progress.
Speaker: Gordon Wallace (University of Wollongong)
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Break 15m
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Speaker Sessions and Seminars: Magnetic surfaces, interfaces and nanostructures - 4
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The Magnetic Properties of Individual Atoms/Molecules on Solid Surfaces 15m
Control over charge and spin states at the single atom and molecule level is crucial not only for a fundmental understanding of charge and spin interactions but also represents a prerequisite for development of spin tronics. Recently, we demonstrate that the Kondo resonance of manganese phthalocyanine (MnPc) molecules can be reversibly switched via a robust route through chemical absorption and desorption of a single hydrogen atom, and further the site-dependent g factor mapping was revealed within a dehydrogenated-MnPc molecule within intramolecular resolution. The modulation of magnetic properties and Kondo effect of magnetic adatoms on graphene layer was also studied, and we show the first discovery of a Kondo effect caused from a magnetic impurities doped in graphene layer in experiment. Finally I will present the investigation of different inter-atomic spin interactions of artificial Mn nanolusters registered on graphene with magnetic field dependent inelastic spin excitation spectroscopy. All the dimers observed exhibit an antiferromagnetic singlet ground state and spin transitions from singlet to triplet states, but their AFM coupling strength shows unique dependence on their site registration on the graphene template. More intriguing spin coupling can be found in graphene mediated non-collinear Mn trimer. The exchange energies cannot be understood by direct spin exchange mechanism, but suggesting the non-local Ruderman-Kittel-Kasuya-Yosida (RKKY) indirect spin exchange mechanism through substrate modulation, which has not yet been achieved in graphene so far.The works open up new opportunities to access local spin properties and quantum states at the ultimate molecular limit.
*Presenting and Corresponding Author: hmguo@iphy.ac.cn
1) J. D. Ren, H. M. Guo, and H. J. Gao et al, Phy. Rev. Lett. 119, 176806 (2017)
2) J. D. Ren, H. M. Guo, and H. J. Gao et al, Nano Lett. 14, 4011 (2014)
3) J. D. Ren, X. Wu, and H. M. Guo et al, Appl. Phys. Lett. 107, 071604(2015)
4) L. W.Liu, K. Yang, and H. J. Gao et al, Sci.Rep.3, 1210 (2013)
5) L. W. Liu, K. Yang, and H. J. Gao et al, Phys. Rev. Lett. 99, 106402 (2015)Speaker: Prof. Guo Haiming -
10:15
Modifying the magnetic reversal mechanism of an exchange biased partially oxides MnxOy/Ni80Fe20 bilayer through oxygen ion implantation 15m
Thin film sample Si(001)//SiO2/Ni80Fe20/MnxOy were ion sputtered. These sputtered samples were oxygen implanted using 8 keV ions at fluences of 1016, 1017 and 1018 ions/cm2 in order to modify the exchange bias effect at the MnxOy/Ni80Fe20 interface. The magnetic, crystallographic and chemical properties of the sample were studied before and after the implantations using transmission electron microscopy, X-ray reflectometry, magnetometry and polarised neutron reflectometry. The results show an overall improved exchange bias and coercivity of the ion implanted samples. We observed a drastic magnetic and composition phase transition of MnxOy as a function of ion fluence. The 1017 ions/cm2 implanted sample showed the highest improvement in exchange bias field and was therefore selected for studying its detailed spin reversal behaviour using polarised neutron reflectometry before and after implantation. The results reveal a coexistence of coherent and non-coherent magnetic spin reversal in the as-grown sample and a solely coherent spin rotation reversal mechanism for the implanted sample.
Speaker: Ji Zhang (UNSW) -
10:30
Iron spin-reorientation transition by dynamic interface alloy formation with Mn 15m
Magnetic thin film heterostructures have been widely studied for fundamental interests in the emergence of novel magnetic phenomena as well as their promising practical applications. The heterointerface interaction plays a dominant role in the development of interesting electronic and magnetic properties. The coupling at the heterointerface strongly relies on the interfacial structure on the atomic scale such as atomic roughness, steps and intermixing, which could degrade electronic and magnetic interactions considerably compared to the theoretically predicted ideally-abrupt interface. However, little comprehensive study that takes overall interfacial factors including electronic hybridization on the atomic scale into account and identifies their individual roles has been conducted so far.
We use scanning tunneling microscopy (STM) and x-ray absorption spectroscopy/x-ray magnetic circular dichroism (XAS/XMCD) as complementary tools to study the correlation between the microscopic interface properties and macroscopic magnetic properties of Mn overlayers on an fcc Fe thin film. Successive atomically-resolved in situ STM characterizations of the surface structural and electronic properties during the growth of the Mn overlayer in ultra high vacuum (UHV) give crucial information on the dynamical process of the heterointerface formation. Element-specific and quantitative observations of electronic and magnetic properties by in situ XAS/XMCD measurements can be linked with microscopic origins of the heterointerface characteristics.
Our fcc Fe thin films are grown on Cu(001) with Mn overlayers in UHV. Magnetic properties of the ferromagnetically-coupled top two layers in the fcc Fe film on Cu (001) are quite sensitive to the local lattice strain even on the atomic scale. Thus, the fcc Fe thin film could highlight the role of atomic-scale interfacial factors with the Mn overlayers.
We find in the XMCD measurements that the Fe layer in Mn/Fe thin film heterostructure exhibits a two-step SRT from out-of-plane to in-plane magnetization with increasing the Mn coverage. The origin of the observed two-step SRT is identified by separately evaluating the roles of entangled interfacial factors using STM with atomic-resolution imaging and spectroscopic capabilities. At low Mn coverages (< 1 ML), a considerably rough heterointerface due to the formation of the disordered alloy drastically weakens the out-of-plane magnetization of the Fe layer, accordingly triggering the first step of the SRT. In the second-step SRT, the in-plane magnetic anisotropy of Mn/Fe thin film heterostructures is gradually enhanced up to ~ 3 ML Mn coverage. At the same time, an ordered FeMn alloy is formed with the increase of the Mn coverage. With the help of our first-principles calculations, we attribute the stabilization of the in-plane magnetization dominantly to the electronic hybridization of the Fe layer with the ordered alloy at the heterointerface.
The present results demonstrate that microscopic characterizations by STM can be effectively integrated into macroscopic ones by XAS/XMCD to achieve a comprehensive understanding the relation between the magnetic properties and the dynamic heterointerface formation. Furthermore, a considerable enhancement of the magnetic anisotropy of the Fe layer across the second-step SRT will provide a new perspective on the materials design using the interfacial alloy to reinforce magnetic thin film heterostructures.Speaker: Prof. F. Komori
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Speaker Sessions and Seminars: Plasma Science and Techniques - 1
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Small high density plasma sources for Focussed Ion Beam Applications 45m
Oregon Physics has developed the HyperionTM system of high brightness plasma ion sources which are now being used on Focused Ion Beams and TOF-SIMS around the world. The original research on the plasma source ion beam system was done at the Space Plasma Power and Propulsion Laboratory at the Australian National University. These plasma sources are ten times brighter than present sources and reduce the time necessary for analysis from days to hours. They are also more reliable and can be focused down to smaller spots. The development of these sources, especially the optimization of the rf antenna design and extraction geometry will be described. Extraction of positive ions is used for reverse engineering on the nano-metre scale and negative ions are used for Time of Flight Secondary Ion Mass Scectroscopy (TOFSIMS).
SIMS uses a beam of primary ions (typically O-) focused onto a target. Sputtered secondary ions are measured by mass spectrometer which can detect elements and their isotopes in the low parts per billion (10-9 or ng/g) range. Particles as small as a few 100 nanometres can be analysed.
Time of Flight (TOF)SIMS measures the time of arrival of the secondary ions at the detector, which depends on their mass yielding an extremely good high mass resolution. It can detect: cocaine in urine, benzodiazepines (eg. valium) in hair and gunshot residues in fingerprints even after strenuous washing! Additionally, TOF-SIMS can simultaneously detect cocaine in the presence of other drugs (i.e. flurazepam (a benzodiazepine hypnotic) and chlorpromazine (used for psychosis and heroin withdrawal) in urine. It is possible to relate the TOF-SIMS fingerprints to the evidence found at the crime scene, which can be considered as examination of forensic evidence transfer. Elemental composition of anthrax spores using TOF-SIMS has been carried out by Weber et. al. at LLNL. This is of use in assessing the origin of bio-weapons.Speaker: Rod Boswell (ANU)
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Speaker Sessions and Seminars: Thin Films - 4
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Performance of ZnGa2O4 deep ultraviolet photodetectors 30m
A single-crystalline ZnGa2O4 epilayer was successfully grown on c-plane (0001) sapphire substrate by MOCVD for application as high performance metal-semiconductor-metal (MSM) visible-blind deep-ultraviolet (DUV) photodetector (PD). The optimized growth parameters for the growth pressure and growth temperature were 15 torr and 650 oC, respectively. The result presented here demonstrate the performance of as grown and annealed at 800 oC in a nitrogen environment for 1 h ZnGa2O4 epitaxial films photodetectors. Compared to as grown ZnGa2O4 film improved UV properties of annealed ZnGa2O4 film were observed. It was found that as-grown films exhibit the highest density of cation-anion pair defects, which could contribute deep trapping centers that increases the generation current or trap assisted leakage current delaying the response and recovery times of as-grown PD devices. However, post-annealing provides sufficient energy to reduce the cation-anion pair defects in the as-grown samples to repair each other. The magnitude of the photocurrent and the rise time are found to increase considerably with decrease number of trap levels. At 5 V bias voltage, the annealed ZnGa2O4 PD shows superior performance with an extremely low dark current of 1 pA, a responsivity of 86.3 A/W corresponding, cutoff wavelength of 280 nm, a highest DUV-to-visible discrimination ratio up to 107 upon 233 nm DUV illumination. The rise time of annealed ZnGa2O4 PD was 0.5 s and PD has been shown a relatively slow decay time of 0.7 s. In this study, our approach provides a simple and controllable method to fabricate single crystalline ZnGaO films based high-performance DUV photodetectors, which has been rarely reported.
Speaker: Prof. Ray-Hua Horng (National Chiao Tung University, Institute of Electronics) -
10:30
Broadband extraordinary optical transmission in a narrow subwavelength gap of infrared wire-grid-polarizers 15m
Wire-gird polarizers (WGPs) have placed central roles in a variety of applications such as imaging system, display, and spectroscopy. However, traditional WGPs show low transmission efficiency in midwave infrared (MWIR) and longwave infrared (LWIR) spectral regions, which is attributed to a large index contrast between air and IR-transmitting substrates such as silicon (Si) and germanium (Ge). In this study, we demonstrate the WGPs, where a metallic film is selectively deposited on a Si nanograting substrate by utilizing oblique angle deposition (OAD), with the capability to reach ~80% transmission efficiency over a broad range of the IR spectrum from 3 μm to 8 μm. It is noticeable that increasing a duty cycle of the nanogratings leads to higher transmission efficiency, which is obviously different from those observed in existing WGPs where an array of the metallic wires is directly patterned on a flat substrate. Optical properties of the proposed WGPs are thoroughly explored by studying the field distribution into the WGP structures using a finite-difference time-domain (FDTD) simulation and an admittance diagram employing effective medium approximation with a thin film simulation. A significantly enhanced electric field is formed in a narrow subwavelength gap, which is found to be responsible for achieving the broadband extraordinary optical transmission. The presented approach may open the door to various applications including recognition, remote sensing, and target tracking.
Speaker: Wonyoung Kim (Inha University) -
10:45
Simple linear relationship between reactive gas flow rate and discharge power at mode transition on reactive sputter deposition of metal oxides 15m
Reactive sputter deposition process has become a very popular method to prepare oxide and other compound films in both academic and industrial fields. In the metal oxide deposition using this process, for example, a metal target is sputtered while oxygen gas is introduced into the deposition chamber to form the oxide on the substrate surface. In this process, two distinct operation modes appear corresponding to the target surface condition. In the “metallic mode”, where the sputter etching of the target surface predominates the oxidation, a fast deposition rate is available while the deposited films tend to be off-stoichiometric or rather metallic. In the “oxide mode”, where the relationship between the etching and oxidation rate is reversed, stoichiometric films are obtained at the cost of low deposition rate.
When applying a constant discharge power, mode transitions are observed by increasing or decreasing the O2 gas flow rate; metal to oxide (M2O) transition and oxide to metal (O2M) transition, respectively. In many cases, the transitions occur like state jumps and show a hysteresis. Namely, M2O transition occurs at a higher O2 gas flow rate than O2M one. This phenomenon has been well described by the Berg’s model, in which the gettering of the reactive gases with the deposited metals on the chamber wall plays an important role [1]. Therefore, a cut-and-try approach has been necessary to find the best process parameters because each industrial deposition equipment has its own geometric configuration.
We have studied the mode transition behavior of Ti-Ar/O2 and V-Ar/O2 systems experimentally, and found a simple linear relationship between the O2 flow rate and discharge power. The discharge was generated by a DC power supply, and the discharge voltage was monitored to detect the mode transition [2]. Two kinds of experimental operations were carried out: one is the constant power operation with changing O2 flow rate, and the other is the constant flow rate operation with changing discharge power. Both were executed at several powers and flow rates, respectively, and the transition points were plotted in XY graph with flow rate and discharge power coordinates. The M2O and O2M transition points, irrespective of the kind of operation, lay on two corresponding straight lines which pass through the origin. It implies that the total mode transition can be predicted by a few pilot experiments.
As described, the mode transition is governed by the balance between the etching rate and the oxidation rate of the target surface. Therefore, our result strongly suggests that the target etching rate is proportional to the target power. This could be understood by considering the I-V relationship of the magnetron discharge (a kind of abnormal glow discharge) and the incident ion energy dependence of the sputtering yield. In the presentation, the effects of other experimental parameters, e.g. Ar gas pressure and the system pumping speed, will also be discussed.- Berg, et al., JVSTA 5 (1987) 202.
- Depla, et al., JAP 101 (2007) 13301.
Speaker: Prof. Takeo Nakano (Seikei University)
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Morning Tea 30m
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Speaker Sessions and Seminars: Biosurfaces, Interfaces & Nanostructures - 1
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Antimicrobial nanobiomaterials for scaffolds and medical devices 45m
Tissue engineering and medical implants hold great potential to restore lost tissue functions in the human body. In tissue engineering, biomaterial constructs may play many important roles, including providing space for tissue growth, acting as scaffolding for cell attachment and migration, mimicking native tissue microenvironments and delivering bioactive signals. However, one significant challenge in using biomaterials in the body is the potential for formation of drug-resistant infections and biofilms on implant surfaces, which lead to device failures, multi-billion dollar costs to the health system and adversely affect the lives of millions of patients. Antimicrobial inorganic nanomaterials are an attractive alternative to antibiotic drugs as they can attack microbes via multiple mechanisms, limiting the microbes’ ability to develop resistance. We have thus investigated the potential of selenium nanoparticles as antibacterial biomaterials with much lower cytotoxicity than the commonly used silver nanoparticles. The nanoparticles’ antibacterial properties depend strongly on their size, and an optimal size range exists for low cytotoxicity and strong antibacterial properties. Hydrogel scaffolds with tailored interconnected porous architectures and mechanical properties are produced through combinations of gas foaming and thermally induced phase separation. Scaffolds decorated by in situ selenium nanoparticle formation from solution impact both Gram-positive (drug sensitive and drug resistant) and Gram-negative bacteria, causing cell damage including membrane permeabilisation. Selenium-based nanomaterials are shown to be promising agents for a range of antibacterial biomaterial applications, including in chitosan scaffolds, which show potential as scaffolds to aid wound healing.
Speaker: Dr Andrea O'Connor (University of Melbourne)
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Speaker Sessions and Seminars: Plasma Science and Techniques - 2
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Atmospheric pressure plasmas for the design and tailoring of surfaces and coatings : from fundamental understanding to dedicated surface properties. 30m
Functional coatings can nowadays be synthesized by atmospheric plasma, which opens interesting possibilities for industrial applications. Antibacterial, anticorrosion, optically active, biocompatible, self-cleaning, superhydrophilic, superhydrophobic, sticky or repellent surfaces can be obtained. However, the still mostly empirical approach used (study of the change in the coating chemistry and properties as a function of the plasma parameters) and the many references to low pressure plasma polymerization theories lead to some limitations in the development of new coatings. In the talk we will present another approach, based on a deeper understanding of the physics and chemistry of the plasma itself, and its consequences on the growing film. The drastic effect of the chemistry of precursors and of the choice of the plasmagen gas (argon or helium) on the chemistry, texture and properties of the resulting coatings will be shown. Examples of fluorinated coatings, acrylates, PEG, and ion-exchange membrane films will be described. The plasma phase, or its post-discharge, is studied using atmospheric mass spectrometry (MS), optical emission spectroscopy (OES), and electrical measurements. The obtained coatings were characterized using infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), (dynamic)water contact angle (WCA), atomic force microscopy (AFM), and profilometry.
Speaker: François Reniers (Université libre de Bruxelles)
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Speaker Sessions and Seminars: Surface Science - 1
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Modelling Driven Discoveries in Molecular Spectroscopy 45m
A significant number of scientific discoveries in the past was driven by experiment with several exceptions. The coming industry 4.0 era will be digital and computer simulation driven. Physical properties of almost all materials should be predictable, in principle, by solving the quantum-mechanical equations governing their constituent electrons. Such calculations require only a small number of chemical elements in appropriate positions through forces. This presentation will cover a broach spectrum of simulation driven discoveries in recent years at Swinburne University through international collaboration. In particular, the narrative of research collaboration leading to breakthrough of the structure of ferrocene using IR spectroscopy will be presented (University of Melbourne and Australian Synchrotron). The X-ray photoemission spectroscopy (XPS) of biomolecules in collaboration with Elettra-Sincrotrone, Trieste (Italy) will be discussed. I will also present primary results of the recent development on interactions between single molecule and metal surfaces.
Speaker: Prof. Feng Wang (Swinburne University of Technology)
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Lunch 1h
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Plenary: Ewa Goldys
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Using light, high energy radiation and theranostic nanomaterials to engineer interactions with biological systems 1h
The Australian Research Council Centre of Excellence for Nanoscale Biophotonics draws on key advances of the 21st century, nanoscience, and photonics to help understand life at the molecular level.
This talk will focus on next-generation nanotechnologies developed in our Centre for probing, imaging and interacting with the living systems. These address the key challenges of ultrasensitive detection of key analytes in real environments, molecular complexity, and the requirement for interventions in deep tissue.Theranostic nanomaterials simultaneously facilitate diagnostics including molecular sensing and active interventions required in therapies. I will discuss how our nanomaterials can produce light and interact with cells when stimulated with high energy radiation, and how this interaction can be quantified. The crossing of length scales inherent in radiotherapy combined with such nanomaterials forms powerful building blocks for innovative cancer treatments.
Speaker: Ewa Goldys (University of New South Wales)
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Break 15m
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Speaker Sessions and Seminars: Biosurfaces, Interfaces & Nanostructures - 2
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Studying Structure at the Liquid/Liquid Interface by Neutron and X-ray Scattering. 30m
The investigation of structure at the liquid/liquid interface is of prime importance in a number of physico-chemical areas both fundamentally and practically. This presentation will focus on x-ray and neutron scattering approaches to studying structure and molecular conformation at planar oil/water interfaces. The oil/water interface is crucial to many industrial systems, for example emulsions (food, cosmetics, drug delivery and others), chemical extraction (both aqueous to organic and the subsequent back extraction).
After outlining technical aspects and alternative model systems I will discuss our current work on tailorable nanoemulsions (TNE) for drug delivery. The TNEs consist of an oil in water emulsion where the interface is stabilised by a rationally designed single alpha helix peptide (AM1). To the AM1 stabilised emulsion a related four-helix peptide (DAMP4) is added. The DAMP4 can be linked to a range of biologically functional elements including antibodies or protein resistant molecules. The arrangement of the AM1 and DAMP4 at the oil/water interface and competition between the two species are important questions, the answers to which help to guide the TNE design. Furthermore, the presentation, conformation and orientation of the antibody into the aqueous phase impacts upon the TNE design and ultimately activity.Speaker: Stephen Holt (Australian Nuclear Science and Technology Organisation) -
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Hierarchical biomimetic porous tantalum fabricated by liquid metal dealloying for biomedical applications 15m
Robust biological activity and rapid osseointegration plays an important role in implant stability and fixation in order to deliver better surgical outcomes for patients. Hence, closely mimicking the topological features of natural human bone can lead to greater osseointegration at the bone-implant interface. Here, we have introduced a selective corrosion based method to synthesise a multi-scale open porous surface coatings via liquid metal dealloying and microstructure control. Liquid metal dealloying offers a versatile method to rapidly produce unique hierarchical surface coatings with tuneable porosity, ligament structure and layer thickness. This is demonstrated by creating a number of open porous Ta coatings with nano-to-micro scale microstructural characteristics by dealloying in liquid Bismuth melt. The effect of precursor microstructure, composition and processing conditions on the ligament structure and coating thickness were discussed in detail. The resultant porous structure due to the careful control of the precursor composition and microstructures presents a hierarchical morphology with bimodal pore distribution, which results in a higher porosity and surface-area-to-volume ratios. The porous coatings achieved in this work consists of bimodal porosity with interconnected nano-porosity within the range of 70-500 nm and micro-scale porosity, ranging from 1-10 m, which is driven by precursor microstructure control. The effect of temperature, immersion time and grain-boundaries, and its effect on dissolution, ligament coarsening and stability of the coatings are also discussed in detail. Overall, the liquid metal dealloying process provides a rapid fabrication process for designing multi-scale hierarchical porous structures with tuneable functionality.
Speaker: Mr Sanka Mendis (RMIT University/CSIRO)
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Speaker Sessions and Seminars: Surface Engineering - 1
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Anti-fouling and Slippery Properties of Lubricant-Infused Surfaces 45m
My group’s research focuses on controlling the nano- and micro-scale structure and chemistry of surfaces to produce advanced functional behaviour. In this talk I will describe a family of bio-inspired surfaces - slippery lubricant-infused porous surfaces - that have the potential to decrease our energy needs by contributing drag-reducing,1 self-cleaning,2 and anti-fouling properties.3 In all cases, our aim is to achieve functional coatings using approaches that are simple to realise and potentially scalable.
References:
1. Lee, T.; Charrault, E.; Neto, C., Adv. Colloid Interface Sci. 2014, 210, 21-38.
2. Scarratt, L. R. J.; Hoatson, B. S.; Wood, E. S.; Hawkett, B. S.; Neto, C., ACS Appl. Mater. Interfaces 2016, 8, (10), 6743-6750.
3. Ware, C. S.; Smith-Palmer, T.; Peppou-Chapman, S.; Scarratt, L. R. J.; Humphries, E. M.; Balzer, D.; Neto, C., ACS Appl. Mater. Interfaces 2018, DOI: 10.1021/acsami.7b14736.Speaker: Chiara Neto (University of Sydney)
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Speaker Sessions and Seminars: Surface Science - 2
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Observation of a resonant-type ground state in graphene intercalated with cerium 30m
The interaction between a magnetic impurity and metallic background provides a key to understand many-body interaction and its effect on the electro-magnetic properties of a material. Such an interaction leads to the formation of a resonant-type many-body ground state, so-called Kondo resonance, that is enhanced at low temperatures. We investigate temperature-dependent electron band structure of graphene intercalated with cerium, which provides metallic electrons and localized 4f electrons, respectively. Cerium intercalation induces new spectral weight in graphene band structure that becomes stronger at low temperature, which is attributed to the formation and development of the new many-body ground state.
Speaker: Prof. Choongyu Hwang (Pusan National University) -
15:00
Capturing interface processes at the atomic scale by high-speed surface X-ray diffraction 15m
Surface X-ray diffraction (SXRD) is one of the most powerful methods that can determine the atomic structure of buried interfaces non-destructively. It is widely used to analyze the structure of solid-liquid and solid-solid interface to understanding the interface processes such as electrochemical reaction and thin film growth. A drawback of SXRD is that the measurements are often time-consuming: the data acquisition time is several tens of minutes or more even when a state of the art two-dimensional detector is used, which is in most cases longer than the relaxation time of the structural changes. Capturing the dynamical behavior of interfaces with a sufficient temporal resolution still remains challenging.
We have developed a high-speed technique which can acquire a wide range of SXRD profile at once within seconds or less [1]. The method uses an energy-dispersive convergent X-rays, instead of a conventional monochromatic collimated X-rays. The combination use of the energy-dispersive X-rays and a two-dimensional detector allows the simultaneous acquisition of a SXRD profile without moving the specimen and detector, enabling the real-time monitoring of interface processes [2, 3].
In this talk, we show the capability of the high-speed technique for capturing the atomic-scale processes at buried interfaces: structural change of Pt(111) electrode surface during electrochemical decomposition of methanol, and the atomic-scale growth process of topological insulator Bi2Se3 thin film.References
1. T. Matsushita, T. Takahashi, T. Shirasawa, E. Arakawa, H. Toyokawa, and H. Tajiri, J. Appl. Phys. 110, 102209 (2011).
2. T. Shirasawa, W. Voegeli, E. Arakawa, T. Takahashi, and T. Matsushita, J. Phys. Chem. C 120, 29107 (2016).
3. T. Shirasawa, T. Masuda, W. Voegeli, E. Arakawa, C. Kamezawa, T. Takahashi, K. Uosaki, and T. Matsushita, J. Phys. Chem. C 121, 24726 (2017).Speaker: Tetsuroh Shirasawa (National Institute of Advanced Industrial Science and Technology)
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Afternoon Tea 15m
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Speaker Sessions and Seminars: Surface Engineering - 2
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Dye Giant Absorption and Light Confinement Effects in Porous Bragg Microcavities 15m
This work presents a simple experimental procedure to probe light confinement effects in photonic structures. Two types of porous 1D Bragg microcavities with two resonant peaks in the reflection gap were prepared by physical vapor deposition at oblique angle configurations and then infiltrated with dye solutions of increasing concentrations. The unusual position shift and intensity
drop of the transmitted resonant peak observed when it was scanned through the dye absorption band have been accounted for by the effect of the light trapped at their optical defect layer. An experimentally observed giant absorption of the dye molecules and a strong anomalous dispersion in the refractive index of the solution are claimed as the reasons for the observed variations in the microcavity resonant feature. Determining the giant absorption of infiltrated dye solutions is proposed as a general and simple methodology to experimentally assess light trapping effects in porous photonic structuresSpeaker: Dr Francisco Yubero (ICMS, CSIC)
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Speaker Sessions and Seminars: Surface Science - 3
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Entropy-Driven Spontaneous Dissociation of Fluoroacetic Acids in Ice 30m
Ordinary chemical reaction is difficult to occur in ice at low temperature, where atoms and molecules are frozen in position with minimal thermal energy and entropy. Contrary to this general knowledge, fluoroacetic acids dissociate spontaneously in ice, according to studies with reflection absorption infrared spectroscopy and H/D isotopic exchange experiment. Fluoroacetic acids dissociated almost completely to ions in ice (both amorphous solid water and crystalline ice) at 8-140 K, which indicates a significant increase of the acidity as compared to that in aqueous solution at room temperature. Formic acid and acetic acid did not dissociate under the same conditions. The enhanced dissociation of fluoroacetic acids is attributed to the high mobility of excess protons in ice and its entropy-increasing effect.
Speaker: Prof. Heon Kang (Seoul National University) -
16:00
Diamond Surface Functionalization and Doping for Carbon-based Electronics 30m
Despite being a bona-fide bulk insulator, the surface of diamond presents a versatile platform for exploiting some of the extraordinary physical and chemical properties of diamond, leading to applications such as chemical/biological sensing and the development of high-power and high-frequency field effect transistors (FETs) [1]. On one hand, bare diamond (001) surfaces are reactive, and can be readily functionalized by organic molecules through chemical reactions such as cycloaddition reaction. Hydrogen-terminated diamond surface, on the other hand, develops an intriguing two-dimensional (2D) p-type surface conductivity when exposed to appropriate surface adsorbate layer such as atmospheric water as a result of the surface transfer doping process.
In the first part of the talk, I will describe our recent work in the engineering of diamond surface properties through surface functionalization [2]. The implications of these new diamond surface terminations to potential applications in photochemistry and quantum sensing will be discussed. In the second part of the talk, I will describe our work on the surface transfer doping of diamond by a variety of solid-state acceptors [3]. I will show that by interfacing diamond with suitable materials a 2D hole conducting layer with metallic transport behaviours arises on diamond. Magnetotransport studies at low temperature reveal phase coherent transport in the 2D channel represented in the form of weak localisation and antilocalisation, and are analysed in the context of spin-orbit coupling induced by Rashba effect. We also demonstrate that this surface conducting channel can be exploited to build diamond surface electronic devices such as metal-oxide semiconductor FETs (MOSFETs). Lastly, the prospects for constructing novel quantum devices on diamond surface by making use of this highly tunable 2D conducting layer on diamond are also explored.
References:
- Pakes, C. I., Garrido, J. A., & Kawarada, H. MRS Bulletin, 39, 542-548 (2014).
- Schenk, A. K., Tadich, A., Sear, M. J., Qi, D.-C., Wee, A. T. S., Stacey, A., & Pakes, C. I. Nanotechnology, 27, 275201 (2016).
- Crawford, K. G. et al. Applied Physics Letters, 108, 042103 (2016).
- Crawford, K. G. et al. Scientific Reports, 8, 3342 (2018).
Speaker: Dr Dongchen Qi (Queensland University of Technology) -
16:30
Adsorption and absorption of hydrogen in Titanium dioxide 30m
Titanium dioxide (TiO2) surfaces are of interest and importance in both physical and chemical aspects including photocatalytic H2 generation, hydrogen sensors, and two-dimensional electron gas formation. Titanium dioxide reveals polymorphism of rutile and anatase. Upon interaction with TiO2 surfaces, hydrogen might adsorb on the surface and diffuse into the interior of TiO2, which significantly affects the electronic structure of TiO2. In these regards, interaction of hydrogen with TiO2 surfaces is of particular importance. We have studied the hydrogen adsorption and absorption in the rutile TiO2(110) and anatase TiO2(101) surfaces with nuclear reaction analysis (NRA) and ultraviolet photoemission (UPS). Whereas the former allows us to quantify hydrogen in the sample in a depth-resolved manner [1], the latter provides us with the information on the electronic occupied and unoccupied states.
When the nearly stoichiometric surfaces of rutile TiO2(110) and anatase TiO2(101) are exposed to atomic hydrogen, NRA shows adsorption of hydrogen with a coverage of about 0.5 monolayer [2]. Concomitantly, a decrease in the work function and downward band-bending are observed by UPS suggesting electron transfer from adsorbed hydrogen to the substrates. Upon annealing the samples, the hydrogen amount near the surface is reduced without desorption indicating that hydrogen undergoes diffusion into bulk. When the rutile TiO2(110) surface is exposed to a hydrogen ion beam at 500 eV, an enhanced hydrogen concentration within 10 nm from the surface is detected as compared to the exposure to atomic hydrogen along with an enhanced band-bending. UPS using ultraviolet laser reveals hydrogen-induced features in the unoccupied states, which could be related to photocatalytic activity.References
[1] M. Wilde, K. Fukutani, Surf. Sci. Rep. 69, 196 (2014).
[2] K. Fukada et al., J. Phys. Soc. Jpn. 84, 064716 (2015).Speaker: Prof. Katsuyuki Fukutani (University of Tokyo)
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Speaker Sessions and Seminars: Vacuum Science and Technology - 1
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High resolution and radiation-damage free inverse photoelectron spectroscopy 45m
Despite the importance, limited information has been available about the unoccupied states of organic semiconductors because of lack of a suitable experimental technique. Inverse photoelectron spectroscopy (IPES) is, in principle, an ideal tool to examine the unoccupied states; the electrons are introduced to the sample surface and the photons emitted due to the radiative transition to unoccupied states are detected, which can be regarded as the time-inversion process of photoelectron spectroscopy (PES). Particularly, to determine quantitatively the energies of the unoccupied states of such systems with large exciton binding energy as organic semiconductors, IPES can be a unique technique. In the previous IPES, however, the sample damage to the molecules was unavoidable owing to the electron bombardment and the energy resolution was limited to 0.5 eV.
In 2012, we developed low-energy inverse photoelectron spectroscopy (LEIPS) [1]. In order to reduce the sample damage, the kinetic energy of incident electron is lowered to less than 5 eV which is a typical damage threshold of the organic materials. By reducing the electron energy, the photons emit in the near-ultraviolet range leading to the improvement of energy resolution for the photon detection using the multilayer bandpass filters. Using LEIPS, the unoccupied states can be examined with the accuracy similar to the occupied states using PES.
This novel technique has been applied to organic semiconductors relevant to organic electronic devices [2] and to the fundamental research of organic semiconductors [3]. In the presentation, after discussing the principle of LEIPS, the recent advances of this technique will be reported.
[1] Yoshida, Chem. Phys. Lett. 539-540, 180 (2012); Yoshida, J. Electron Spectrosc. Relat. Phenom. 204, 116 (2015).
[2] Yoshida, Yoshizaki, Org. Electron., 20, 24 (2015); Yoshida, J. Phys. Chem. C, 119, 24459 (2015); Yoshida, J. Phys. Chem. C, 118, 24377 (2014).
[3] Zhong, et al, J. Phys. Chem. C, 119, 23-28 (2015); H. Yoshida, et al., Phys. Rev. B, 92, 075145 (2015); K. Yamada, et al., Phys. Rev. B (accepted).Speaker: Hiroyuki Yoshida (Chiba University) -
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Towards ARPES at the Australian Synchrotron: 3rd Generation Toroidal Angle Resolving Electron Energy Spectrometer 30m
Angle Resolved Photoelectron Spectroscopy (ARPES) is the “complete” photoemission experiment. It simultaneously measures a photoelectron’s kinetic energy, emission angle and sometimes spin, relative to the crystallographic axes, constructing a direct image of the electronic bandstructure. This makes ARPES the most powerful contemporary technique for determining the electronic structure of novel materials. ARPES has been instrumental in the discovery and understanding of new electronic phases of matter. For example, important aspects of the electronic structure of high-Tc superconductors, such as the pseudogap were discovered using ARPES, as was the experimental discovery of three dimensional topological insulators Bi1-xSbx and Bi2(Se,Te)3.
Over the years, a dramatic improvement in the energy and momentum resolution possible with ARPES has occurred as a result of advances in photoelectron analysers and 2D detectors, allowing a range of new physics to be probed. Despite the popularity of ARPES overseas, within Australia it has until now remained as a niche technique due to a small (albeit dedicated) user community. However, the continually growing local interest in studying novel materials with exotic electronic properties has led to the demand for our own synchrotron – based ARPES instrument. Here, an overview of a forthcoming ARPES instrument, an advanced 4th generation “toroidal” electron spectrometer,at the Australian Synchrotron will be given. An advanced helium discharge lamp allows for offline work to be carried out. In contrast to the previous 3rd generation instrument installed at BESSY2, the 4th generation Toroidal Analyser is equipped with a liquid helium cryostat and radiation shielding to allow for ARPES measurements to be conducted with the sample at cryogenic temperatures. An overview of the system’s principles of operation, and sample preparation environment will be given.
Speaker: Anton Tadich
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Poster Session B: Main Hall
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Registration
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Plenary: Christine Charles
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Lab to Launch 1h
Progress in satellite technologies is ongoing and eventually finds applications back on Earth. The global space industry is expecting significant growth based on cheaper launch capabilities and standardised satellite platforms. Thousands of small satellites (such as CubeSats) are expected to be launched over the next decade: a disruptive space revolution boosting Earth imaging, internet, global positioning and space weather forecast capabilities. Electric propulsion (EP) has been an innovative solution in a number of space missions but its scalability remains a challenge. Many mature or under development space propulsion systems could also benefit from more compact and efficient power supplies. Pocket Rocket is an Australian-born miniaturised electrothermal radio frequency plasma thruster which uses environmentally friendly propellant such as argon. A complete end-to-end small satellite industry --- "Lab to Launch" --- is now available wholly within the Trans Australasian Pacific region, thanks to the recent demonstration of Rocket Lab's access to orbit. Groups at the Australian National University, Stanford University and the University of Auckland have joined forces to pave a path to space heritage for Pocket Rocket via the CubeSat platform. The aim is to improve the efficiency of a cold gas thruster in a single and effective manner by improving miniaturized power supplies and gas handling systems while training the next generation of students on radiofrequency, vacuum, power and plasma technologies. These innovations will help the future development of nano-satellite orbit control, attitude control, formation flying and docking capabilities. Most importantly, a lot of interesting physics is left to be uncovered.
Speaker: Prof. Christine Charles (The Australian National University)
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Break 15m
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Speaker Sessions and Seminars: Plasma Science & Techniques - 3
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Development of scalable plasma polymerisation processes 30m
Plasma technology has been used to produce cell culture plastics since the 1960s, but more recently, functionalised surfaces have been developed that provide specific functional groups for immobilisation, or for capturing biomolecules. While these surfaces can be made simply and easily in the lab, producing them at a commercial scale presents a number of challenges.
We present the development and characterisation of a large-area plasma polymerisation pilot reactor system capable of higher throughput than typical lab-scale reactor systems and describe some of the challenges in scaling up plasma systems of this type. The system is compared with a standard lab-scale system using plasma mass spectrometry, ion flux measurements and characterisation of the products be XPS and ToF-SIMS.Speaker: Jason Whittle (University of South Australia)
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Speaker Sessions and Seminars: Surface Science - 4
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Molecular nanoarchitectures from on-surface reactions and assembly 30m
One of the goals of nanoscience is achieving precise control over the structure and function of nanoscale architectures at surfaces. Bottom-up approaches using molecular building blocks present a flexible and intuitive approach to this challenge. Combining the Lego-like modularity of molecules with the epitaxial and reactive influences of surfaces creates a range of opportunities to build exciting new nanoarchitectures.
Reacting molecules on a surface can allow for the fabrication of extended covalent nanostructures with enforced planarity. I will discuss our recent work in studying C-C coupling reactions of halogenated and carboxylated molecules at metal surfaces, where we have been focussing on understanding the effect of heteroatoms in the reaction process and the subsequent formation of oligomeric and polymeric structures, using a combination of scanning tunnelling microscopy, photoelectron spectroscopy and near-edge x-ray absorption fine structure to gain a well-rounded insight into the process.Speaker: Jennifer MacLeod (Queensland University of Technology (QUT))
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Morning Tea 30m
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Speaker Sessions and Seminars: Plasma Science & Techniques - 4
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Mild plasma configuration yielding efficient doping on graphene surface 30m
In this talk, I will present the effectiveness of a mild plasma configuration in order to dope nitrogen on graphene without defect formation. The system is a vertical-type direct-current plasma with parallel electrodes. We change the electrode configuration and adjust the plasma input power and treatment time to utilize various ion-bombardment energies and plasma doses. The up-cathode system with a powered upper electrode and ground lower anode is more suitable than the traditional down-cathode system for efficient plasma doping. This configuration yields a low-energy ion process and thus suppresses high-energy ion-induced damages.
The graphene was prepared by mechanical exfoliation and the doping was performed using ammonia gas. The degree of a structural damage on graphene after the doping was mainly evaluated using Raman spectroscopy. Finally, the structural evolution of graphene and the doping components with respect to the plasma conditions are extensively characterized with Raman spectroscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. The results provide an effective doping condition for doping nanomaterials without plasma-induced damage.Speaker: Prof. Goo-Hwan Jeong (Kangwon National University)
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Speaker Sessions and Seminars: Surface Science - 5
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The Experimental Realization of Polyphony in Borophene 30m
The boom of graphene research, as well as the successful development of high-quality graphene films for industrial applications, has inspired the theoretical prediction and experimental discovery of a number of elemental two-dimensional (2D) materials. Boron (B), the one-electron-lacking neighbor of carbon in the periodic table, is identified by rather different chemistry as compared to C. A mixture of honeycomb units together with triangular units in two-dimensional (2D) sheets was predicted to be more stable. This gives rise to rich allotropy of boron, which is seen in the possibility of its multiple phases in borophene. In this talk, I will introduce the experimental realization of borophene on Ag(111) surface by molecular beam epitaxy (MBE) growth in ultrahigh vacuum firstly. A few different phases relied on the substrate temperature during growth are confirmed. Furthermore, it is found that the crystalline symmetry of substrate can influence the morphology of borophene. The high quality borophene nanoribbons can be formed on an anisotropic substrate - Ag(110). By engineering the interface interactions and the charge transfer between substrate and borophene, we can realize the a purely honeycomb, graphene-like borophene on Al(111) surface. Theoretical calculations show that the honeycomb borophene on Al(111) is energetically stable. Remarkably, nearly one electron charge is transferred to each boron atom from the Al(111) substrate, in contrast to the little charge transfer in B/Ag(111) case. At last, I will show the angle-resolved photoemission spectroscopy measurements on borophene on Ag(111), which revealed Dirac cones in first Brillouin zone, proving the existence of Dirac fermions in borophene.
Speaker: Prof. Lan Chen (Institute of Physics, Chinese Academy of Sciences) -
11:30
Surface-confined polymerisation: synthetic chemistry without a beaker 30m
One of the most intriguing ideas of the last decade is the concept of translating well-known chemical synthesis methods into the realm of surface science. The ability to interrogate individual atoms and molecules by scanning probe microscopies affords new insights into well-established reaction pathways, and in some cases can reveal unexpected and often surprising new structures. Synthesis of polymers via on-surface arene coupling is an intriguing and facile route towards novel 1D and 2D materials. Ullmann coupling has been the most studied of these methodologies, as it offers a convenient and simple way to control the growth of the polymer products by employing the substrate both as the catalyst for initiating the coupling reaction, as well as a template for supporting the product and driving its growth into well-ordered domains.[1]
In this seminar I will describe our longstanding interest in molecular reactions with the aim of producing new interesting and functional materials, such as simple polyphenylenes,[1] industrially-relevant thiophenes,[2,3] and exotic two-dimensional analogues of graphene. [4,5] I will briefly touch on strategies to avoid the chief perceived drawback of Ullmann coupling: that it is not considered to be a ‘clean’ reaction because most surfaces host both the polymer product and the halogen byproducts, the latter of which block catalytic sites on the surface and ultimately act to limit the yield of the product.
References
[1] J. Lipton-Duffin, O. Ivasenko, D.F. Perepichka and F. Rosei. Small 5, 592 (2009)
[2] J. Lipton-Duffin, J. Miwa, M. Kondratenko, F. Cicoira, B. G. Sumpter, V. Meunier, D.F. Perepichka, F. Rosei, Proc. Nat. Acad. Sci 107, 11200 (2010)
[3] I. Di Bernardo, P. Hines, M. Abyazisani, N., J. MacLeod, J. Lipton-Duffin, Chem. Commun. 54, 3723 (2018)
[4] R. Gutzler, L. Cardenas, J. Lipton-Duffin, M. El Garah, L. E. Dinca, C. E. Szakacs, C. Fu, M. Gallagher, M. Vondráček, M. Rybachuk, D. F. Perepichka, F. Rosei
Nanoscale 6, 2660 (2014)
[5] L. Cardenas, R. Gutzler, J. Lipton-Duffin, C. Fu, J. L. Brusso, L. E. Dinca, M. Vondráček, Y. Fagot-Revurat, D. Malterre, F. Rosei, D. F. Perepichka, Chem. Sci., 3, 3263 (2013)Speaker: Josh Lipton-Duffin (Queensland University of Technology)
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Speaker Sessions and Seminars: Vacuum Science & Technology - 2
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Atmospheric-pressure microwave plasma system for cleaning and deposition 15m
Current wet chemical processes for cleaning and painting of metal surfaces require multiple steps including cleaning, degreasing, deoxidizing and anodizing/chemical conversion coating to impart the necessary surface modification all while using chemicals with significant environmental and health hazards. The most common alternative surface modification methods are laser and plasma-based systems. Plasma systems show promise because a single pass can perform both the surface cleaning and the pretreatment of the metal. The development of a single pass, corrosives-free process for both cleaning and pretreatment of metal surfaces requires a simple but robust process. Atmospheric plasma meets these requirements as it can sequentially clean surfaces, provide surface activation for bond formation, and deposit thin film coatings.
The Center for Plasma Material Interaction (CPMI) at University of Illinois has developed novel patented technologies of Evaporative Coatings at Atmosphere Pressure (ECAP). This atmospheric plasma-based system is designed to eliminate chemical waste and remove contaminants using a microwave plasma. The experiments conducted using this system have showed that that it can effectively clean the aluminum surface from heavy oil contamination. Contact angle measurements, XPS and ATR-FTIR techniques were involved to show the cleaning and activation effect of our system. EM field simulations and gas flow modeling were used to predict and set the experimental conditions. With this setup, treatment time under a minute and 400-600 W power is enough to sufficiently clean the aluminum surface. For example, an aluminum sample contaminated with oil layer had a contact angle of 65.02°±0.49°. After a 30 s plasma treatment in Air using 600 W microwave power and distance of 0.45” from the plasma torch, the contact angle decreased to 8.86°±0.06° indicating the contamination removal while making the surface hydrophilic.
A design reiteration of the old system enables an effective coating deposition in addition to the cleaning and activation processes. This allows for deposition of protective and anticorrosive layers using precursors commonly used in ALD and CVD application. Depositions can also be conducted via Cathodic arc deposition technique (or Arc-PVD) enabled by biasing the target filament with HiPIMS.Speaker: Prof. David N. Ruzic (University of Illinois at Urbana-Champaign) -
11:15
Diamond-Edge Gaskets for the Ultrahigh Vacuum Systems 30m
A special designed aluminum diamond-edge (DE-) gasket was applied to seal the aluminum vacuum chamber on the diamond-edge flat (DEF-) flange, instead of the traditional assembly of the aluminum metallic gasket with the ConFlat (CF-) flange, can achieve the ultrahigh vacuum (UHV) specified leak rate < 1x10-10 Pa∙m3/s and the ultimate pressure of < 10-8 Pa. Since both the DE-gasket and the DEF-flange, made of A1050 and A6061T6 aluminum alloys respectively, are manufactured by the CNC machining with the special tools, therefore the cross section of the flanges and gaskets can be made either in circular shape or in other non-circular shapes, e.g. the rectangular, racetrack, or elliptical shapes. For the ultrahigh vacuum systems, the chambers made of aluminum alloys with the DEF-flanges and the aluminum DE-gaskets sealing can be customer-designed and machined easily. No further cleaning for the aluminum chambers is necessary if adopting the oil-free ethanol CNC machining process. The features of the DE-gasket include: (1) flexible dimensional changes from smaller to larger or from uniform to non-uniform, (2) flexible cross section changes from circular to non-circular, (3) wide range of vacuum extends from 1 atm to the ultrahigh vacuum, (4) more tolerance of mounting accommodates the DE-gasket to the flat DEF-flange, (5) DE-gasket can be reused few more cycles if still compressible. The assembly of the DE-gasket and the DEF-flanges provides reliable sealing-capabilities, flexible and easier machining properties, that is applicable for all the UHV systems including the aluminum ones. Several experimental results will be addressed in this presentation.
Speaker: Mr Gao-Yu Hsiung (National Synchrotron Radiation Research Center, Taiwan) -
11:45
Molecular layer formation on cooled sapphire mirrors in KAGRA Japanese gravitational wave observatory 15m
KAGRA is Japanese gravitational wave observatory which is located in the underground site to reduce seismic motion. In order to decrease the mirror thermal fluctuation, four antenna mirrors have to be cooled down. To achieve 20K for mirror temperature, sapphire was chosen as a material of cooled mirrors and their suspension components in the final vibration reduction stage because of its advantages of thermal conductivity and high mechanical Q value at cryogenic temperature.
The requirements of KAGRA vacuum pressure is 1×10^(-7) Pa, or lower, to avoid refractivity fluctuation due to vacuum residual gases. In order to achieve above requirement in huge volume/area of vacuum chambers and ducts, surface processing for reducing outgassing was applied and materials for use as large suspension systems are carefully chosen. Furthermore, by cooling down, cryostat works as cryo-pump so pressure around cryostat becomes quite low.
Recently, it was revealed that the vacuum residual molecules were adsorbed on cooled sapphire mirrors and finally many numbers of molecules form an adlayer. This molecular adlayer works as a kind of optical coating and changes mirror reflectivity depending on its thickness. To investigate the molecular layer formation in KAGRA, a small optical cavity, having high finesse, was installed in KAGRA cryostat and its finesse was monitored for 35
days.Speaker: Mr Kunihiko Hasegawa (ICRR, University of Tokyo)
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Lunch 1h
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Plenary: Atsushi Fujimori
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X-ray dichroism studies of magnetic anisotropies in thin films 1h
Magnetic anisotropy (MA) is one of the most important properties of ferromagnetic materials since it leads to magnetic hysteresis and coercive forces, which are necessary for permanent magnets and information storage devices [1]. MA arises from combined effects of spin-orbit cou-pling (SOC) and anisotropic electronic structure. Soft x-ray dichroism is a powerful method to investi-gate the anisotropic electronic and magnetic states of atoms in solids, at interfaces, and at surfaces, and the effect of SOC on them. Through measurements of x-ray magnetic circular dichroism (XMCD) with varying magnetic field direction including transverse geometry, we have studied the origin of MA in 3d transition-metal oxide (La$_{1-x}$Sr$_x$MnO$_3$) thin films whose MA is controlled by epitaxial strain [2], and in 3d transition metal-heavy metal alloy (L1$_0$-ordered FePt) thin films showing strong perpendicular MA [3].
In the transition-metal-oxide thin films, epitaxial strain from the substrate is shown to induce aniso-tropic distribution of spin-polarized electrons [2], which leads to MA through the orbital magnetic moment anisotropy (OMA). As a reverse process of the strain-induced MA, we have detected a field-induced anisotropic electron distribution using x-ray magnetic linear dichroism (XMLD). In the transition metal-heavy metal alloy thin films, the relationship between the MA and OMA, well-known Bruno relationship, is shown to breakdown [3], and the anisotropic distribution (i.e. quadrupole moment) of spin-polarized electrons, which is unrelated with OMA, is shown to make dominant contribu-tions to MA.
This work has been done in collaboration with G. Shibata, K. Ikeda, Y. Nonaka, Y. Takahashi, K. Ishi-gami, T. Harano, T. Kadono, T. Koide, K. Amemiya, M. Sakamaki, Y. Takeda, M. Suzuki, N. Kawamu-ra, T. Seki, K. Takanashi, M. Kitamura, M. Minohara, K. Yoshimatsu, H. Kumigashira and A. Tanaka.
References
[1] M. J. D. Coey, Magnetism and Magnetic Materials (Cambridge, 2009).
[2] G. Shibata, A. Fujimori et al., npj Quantum Mater. 3, 3 (2018).
[3] K. Ikeda, A. Fujimori et al., Appl. Phys. Lett. 111, 142402 (2017).Speaker: Prof. Atsushi Fujimori (University of Tokyo)
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Break 15m
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Speaker Sessions and Seminars: Electronic Materials & Processing - 1
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Zero resistance materials and technologies 45m
Electrical power consumption occurs because of the resistance to the flow of electrical current. The power lines and transformers as well as information and computation consume more than 20% of the world's electricity. In this presentation, we will discuss the latest development on superconductors and emerging materials in which electrical current can flow without resistance for ultra-low energy consumption technology. A number of emerging electronic materials such as topological insulators, parabolic or Dirac type spin gapless semiconductors (SGSs), Weyl metals with exotic band structures, Dirac type systems or topological Dirac system, and excitonic insulators will be discussed. How to achieve zero resistance transport in spin gapless semiconductor and topological insulators will be presented. Realization of emerging quantum effect such as quantum Hall, Quantum anomalous Hall, quantum spin or quantum anomalous spin Hall effects will be discussed. A few emerging technologies which can drive 2D systems into zero resistance state will be discussed. Furthermore, the ultimate questions in material and property’s design are raised: 1) How many new electronic materials or new electronic properties are still there? 2) What are they? 3) How to create them? I will present a number of new strategies we have developed for the design of new class of materials and properties. We will discuss how new electronic materials can be designed by shaping electronic band structures. To answer the three questions, a very simple model, the codes of matter/materials, based on the three ubiquitous and paramount attributes of all existing matter/materials, charge (Q), spin (S), and moment (K) is introduced. We will introduce a new periodic table which consists of all codes responsible for physical properties. The principles of the codes and their applications in design of new materials and properties will be presented. Many new types of exotic physical states and their possible experimental realizations will be discussed.
This work is supported by Australian Research Council (ARC) through the ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET) and an ARC Professorial Future Fellowship project (FT130100778).
Speaker: Prof. Xiaolin Wang (University of Wollongong)
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Speaker Sessions and Seminars: Nanometer Scale Science & Technology - 1
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Functional surfaces and devices enabled by two-dimensional materials 45m
Two-dimensional (2D) materials and their derivatives have attracted unprecedented enthusiasm during the past decade due to their exceptional mechanical, thermal, optical, and electrical properties not available in conventional materials. This article explores the innovative surfaces of 2D materials, which enable diverse applications of 2D materials by using the one-step mask-free direct laser printing (DLP) method [1]. Our results have demonstrated the great potentials of two-dimensional material films as an emerging integratable platform for ultrathin, light-weight and flexible photonic, electronic and biological devices towards all-optical communication, microscopic imaging, energy storage and biological applications [2-4].
Reference:
[1] H Lin, B Jia, M Gu, Optics letters 36 (3), 406-408 (2011).
[2] X. Zheng, B. Jia, X. Chen, M. Gu, Adv. Mater 26, 2699 (2014).
[3] S. Fraser, X. Zheng, L. Qiu, D. Li, B. Jia, Applied Physics Letters, 107, 031112 (2015).
[4] X. Zheng, B. Jia, H. Lin, L. Qiu, D. Li, M. Gu, Nature Communications, 6, 8433 (2015).Speaker: Baohua Jia (Swinburne University of Technology)
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Speaker Sessions and Seminars: Surface Science - 6
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The role of lattice dynamics in the superconductivity enhancement at FeSe/SrTiO3 interface 15m
The superconducting transition temperature (TC) of monolayer FeSe on SrTiO3 is significantly enhanced to 60-70 K in comparison with the bulk TC of 8 K. To understand the mechanism of the extraordinary interfacial phenomenon, extensive investigations have been carried out with complementary surface analyses techniques. We use the high-resolution electron energy loss spectroscopy (HREELS) to study the system from the perspective of lattice dynamics. Recently we have developed a new strategy for HREELS, which can simultaneously measure the energy and momentum of surface elemental excitations with high energy and angular resolution, as well as detecting efficiency and sampling density. By growing epitaxial FeSe films on SrTiO3, we study the phonon behaviors of FeSe. Although the superconductivity shows dramatic dependence on FeSe film thickness, no change of phonon energy or line width is detected. On the other hand, we detect the Fuchs-Kliewer (F-K) phonon modes of SrTiO3 substrate on FeSe surface. It is revealed that the electric field generated by the F-K phonon can penetrate into FeSe and strongly interact with electrons. With the increase of FeSe thickness, the penetrating field intensity decays exponentially, associated with the superconductivity enhancement weakened. We conclude that the SrTiO3 F-K phonon penetrating into FeSe is essential in the interfacial superconductivity enhancement.
Speaker: Prof. Guo Jiandong (Institute of Physics, Chinese Academy of Sciences) -
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On-surface bottom-up synthesis of azine derivatives displaying strong acceptor behavior 15m
Organic heterostructures based on acceptor-donor molecules on surfaces have become strategic materials due to their huge technological impact in fields such as organic light-emitting diodes (OLEDs), organic field effect transistors (OFETs), or solar cell devices, amongst others. In particular, the charge transfer process promoted by donor/acceptor molecules at the interface with metal electrodes may induce a realignment of the energy levels that can be exploited to tune the transport properties of the system [1].
In the present work, we use on-surface chemistry to synthesize a strong electron acceptor organic molecule directly on a Cu(110) surface [2]. By a thermal annealing process, p-aminophenol (p-Ap) molecules deposited on Cu(110) undergo an azine-coupling reaction. Both, the chemical reaction mechanism and the charge transfer process induced by the substrate were followed by complementary surface techniques (nc-AFM/STM, XPS, NEXAFS and LEED) as well as by theoretical calculations (Fig.1). We observe that Cu(110) catalyzes a chemical reaction between two p-Ap molecules giving rise to a quinoneazine (QAz) molecule. The resulting molecule accepts 1.2e- from the substrate, which brings on a charge redistribution with recovering aromaticity, leading to an azo compound behavior.[1] R. Otero, A. L. Vázquez de Parga, J. M. Gallego, Surf. Sci. Rep. 2017, 72, 105–145.
[2] N. Ruiz del Arbol, I. Palacio, G. Otero-Irurueta, J. I. Martínez, P. de Andrés, O.Stetsovych, M. Moro, P. Mutombo, M. Svec, P. Jelinek, L. Floreano, G. J. Ellis, M. F. López, J.A. Martín-Gago. Andgewvante chimie, in press.Speaker: Prof. jose a. martin-Gago -
14:45
Free-Standing Graphene on 3C-SiC Nanostructures 15m
There is a growing body of literature that recognizes the potential of graphene for use in electronics [1]. However, graphene’s lack of bandgap challenges its remarkable range of applications [2]. Theoretical work suggests that a bandgap might be opened in graphene through quantum confinement, for example in graphene nanoribbons. Thermal decomposition of SiC has proven to be an excellent method to grow transfer-free wafer-scale graphene [3]. Growing graphene on SiC thin films on Si is a cheaper alternative to the growth on bulk SiC. In this research we attempt to manipulate the SiC substrate dimension to grow graphene over nanostructures and use hydrogen intercalation to produce free-standing graphene.
SiC mesas have been fabricated by patterning SiC/Si substrates using Focused Ion Beam (FIB) milling [4]. Hydrogen intercalation procedure has been employed at 600 °C to fabricate free-standing graphene on the structures [5]. Synchrotron radiation near-edge X-ray absorption fine structure (NEXAFS) with core-level photoelectron spectroscopy (PES), scanning tunnelling microscopy (STM), scanning electron microscopy (SEM), and Raman spectroscopy were used to investigate the process. Our result indicates the possibility of growing free-standing epitaxy graphene over SiC nanostructures. However, more research is needed to better understand the impact of patterning procedure on the graphene growth and decrease the damage caused by milling process.
References
[1] M. Kusunoki et al, Journal of the Physical Society of Japan, 84(2015) 121014.
[2] K. Novoselov et al, Nature, 438(2005) 197-200.
[3] B. Gupta et al, Carbon, 68(2014) 563-572.
[4] M. Amjadipour et al, Nanotechnology, 34 (2017) 345602.
[5] M. Amjadipour et al, Nanotechnology, 14 (2018) 145601.Speaker: Mr Mojtaba Amjadipour (Queensland University of Technology)
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Afternoon Tea 30m
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Speaker Sessions and Seminars: Applied Surface Science - 1
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Sulfides, Surfaces and Synchrotrons 45m
The physical and chemical properties of sulfide mineral surfaces and their interactions with aqueous environments and microbes, is crucial to minerals processing. Over the past 30 years surface analysis techniques including X-ray photoelectron spectroscopy (XPS), Auger Electron Spectroscopy (AES), Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), Atomic Force Microscopy (AFM) and X-ray absorption Spectroscopy (XAS) have been used to elucidate the surface properties of sulfide minerals at selected stages during processing. Their use is now commonplace and has driven interest for further development of advanced in and ex situ nano-spectroscopic techniques.
Nanospectroscopic imaging techniques have provided the opportunity to investigate the effects of mineral heterogeneity and interaction of microbes on the distribution of surface chemical products during dissolution. A prototype Electrochemical Nanoreactor, for high resolution spectroscopic imaging in a hydrated and controlled electrochemical state has been developed and used to study the growth of Cu dendrites and the dissolution of pyrite and chalcopyrite in the presence of Af. The results support the preferential attachment of bacteria to pyrite and the modification of its surface with polysaccharides. The technique shows promise for applications in in-situ geomicrobiological and electrochemical research.
Speaker: Prof. Sarah Harmer (Flinders University) -
16:15
XPSSurfA - An Online Open Access XPS Database 30m
X-ray photoelectron spectroscopy (XPS) is a widely used surface analysis technique employed in fundamental research, applied research, service laboratories and industry. Good quality analytical outcomes depend critically on spectral references. Many examples of XPS reference databases exist, including print editions, sets of spectral peak positions drawn from the literature, and digital archives and libraries. We have developed a new digital XPS database comprising survey and region spectra for a range of materials types, collected under a common set of analytical conditions. Detailed metadata are provided for each material and each spectrum, presented using a schema that incorporates the ISO 16243 and 14976 standards, guidelines developed by IUVSTA technical groups, and extensions developed in this work. Spectra are shared under a Creative Commons International (4.0) attribution, non-commercial licence (CC BY-NC) in Kratos (.dset), VAMAS (.vms) and XML (.xml) formats. We will demonstrate the database and its usage, and discuss current case studies incorporating XPSSurfA data.
Speaker: Dr Anders Barlow (La Trobe University) -
16:45
Rapid multivariate analysis of 3D ToF‐SIMS data: graphical processor units (GPUs) for large‐scale principal component analysis 30m
Principal component analysis (PCA) and other multivariate analysis methods have been used increasingly to analyse and understand depth‐profiles in XPS, AES and SIMS[1]. For large images or three‐dimensional (3D) imaging depth‐profiles, PCA has been difficult to apply until now simply because of the size of the matrices of data involved. We have developed two algorithms that improve the speed of PCA for large ToFSIMS datasets[2], and allow these datasets to be of unlimited size. We apply these to perform PCA on full 3D time‐of‐flight SIMS data for the first time[3]. An example is the processing of a 128 × 128 pixel depth‐profile of 120 layers, each voxel having a 70 439 value mass spectrum associated with it. This forms over a terabyte of data when uncompressed. We have implemented this algorithm on a PC having a graphical processor unit (GPU) card containing 2880 individual processor cores. This increases the speed of calculation by a factor of around 4.1 compared with what is possible using a fast commercially available desktop PC having central processing units alone, and full PCA of this terabyte of ToFSIMS data is performed in less than 7 seconds. We show a number of datasets and PCA results, including biological examples and 3D "tomographic" views of the PCA results[4].
[1] M S Wagner, D G Castner, Langmuir 17 (2001) 4649–4660
[2] P J Cumpson et al, Surface and Interface Analysis 47 (2015) 986–993
[3] P J Cumpson et al, Surface and Interface Analyis 48 (2016) 1328-1336
[4] www.youtube.com/watch?v=bUT0kYuad2ESpeaker: Peter Cumpson (Newcastle University)
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Speaker Sessions and Seminars: Electronic Materials & Processing - 2
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Electric Field Tuned Quantum Phase Transition from Topological to Conventional Insulator in Few-Layer Na3Bi 30m
Na3Bi in bulk form represents a zero-bandgap topological Dirac semimetal (TDS), but when confined to monolayer it is predicted Na3Bi is a 2D topological insulator with a bandgap of ~300 meV.1 Application of an electric field to few-layer Na3Bi has been predicted to induce a topological phase transition, opening up the possibility of creating new types of electronic switches known as 'topological transistors'.2 However, opening a bandgap in TDS has proven elusive, as efforts to grow thin films have only succeeded in growing 15-20 nm films that remain zero-bandgap semimetals.
In this talk I will discuss our efforts in growing epitaxial few-layer Na3Bi via MBE, and then subsequent measurements of the electronic structure and response to an electric field using scanning probe microscopy/spectroscopy and angle-resolved photoelectron spectroscopy. We demonstrate that few-layer Na3Bi is a 2D topological insulator with a bandgap >400 meV. Furthermore, via application of an electric field the bandgap can be tuned to semi-metallic and then re-opened as a trivial insulator with bandgap greater than 100 meV. The electric fields required to induce this transition are below the breakdown field of many conventional dielectrics, making the creation of a topological transistor based on a few-layer TDS within reach.
1 C. Niu, et al., Phys. Rev. B 95, 075404 (2017)
2 H. Pan, et al., Scientific Reports 5, 14639 (2015)Speaker: Mark Edmonds (Monash University) -
16:00
Electronic Structure and Electron Dynamics in Single-Layer Transition Metal Dichalcogenides 30m
The size of a band gap determines the suitability of a material for use in different applications such as computers or in solar cells. In the case of artificial two-dimensional (2D) materials, such as graphene or single-layer (SL) transition metal dichalcogenides (TMDCs), electronic properties, including the band gap, are drastically different from their parent compounds, where dimensionality is not reduced.
The electronic properties of 2D materials do not only depend on the material, but also on its environment, for example, the substrate it is placed on. By changing the dielectric properties of the substrate or the carrier concentration in the material, the band gap size can be modified. Besides control of the band gap, control of the spin- and valley-degrees of freedom has been suggested as a new, potential tuning knob for carrier dynamics, and SL TMDCs, such as SL MoS2 and WS2, are particularly promising candidates for new spin- and valley-tronic devices. This is due to the breaking of the inversion symmetry in their crystal lattice, a strong spin-orbit coupling, and a direct band gap at the K and K' valleys in their electronic structures.
In order to obtain information about ultrafast carrier dynamics and valley-degrees of freedom, it is necessary to probe the samples in a manner that can provide both time and angular resolution. The time- and angle-resolved photoemission spectroscopy (TR-ARPES) technique provides exactly that. TR-ARPES is, however, limited by the technical requirement for high photon energies, since the interesting part of the aforementioned materials' electronic structures is located at the 2D Brillouin zone boundary. This technical limitation was recently overcome with the arrival of ultrafast high harmonic laser sources. These sources can be used to directly access the size and character of the electronic band gap in a semiconducting 2D material, while in the case of 2D metallic layers, the effect of the low dimensionality on electronic instabilities such as charge density waves and superconductivity can be investigated.
This talk will cover single layers of MoS2, WS2 and TaS2 epitaxially grown on Au(111), Ag(111) and graphene. Furthermore, technical requirements, the experimental system and growth procedures will be presented, along with the future experimental directions.Speaker: Dr Antonija Grubisic-Cabo (Monash University) -
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Defects physics in emergent 2D material SnSe with binary black phosphorus lattice 30m
In this talk, we will show the pronounced effects of various defects in determing the physical properties of the emergent 2D material SnSe with binary black phosphorus lattice. SnSe has been reported with record-breaking thermoelectric conversion efficiency very recently. However, to date a comprehensive understanding of the electronic structure and most critically, the self hole-doping mechanism in SnSe is still absent. We for the first time fully unfold the highly anisotropic electronic structure of SnSe by angle-resolved photoemission spectroscopy, which reveals a unique pudding-mould-shaped valence band with quasi-linear energy dispersion. We prove that p-type doping in SnSe is extrinsically controlled by local phase segregation of SnSe2 microdomains via interfacial charge transferring. The multivalley nature of the pudding-mould band is manifested in quantum transport by crystallographic axis-dependent weak localisation and exotic non-saturating negative magnetoresistance. Strikingly, quantum oscillations also reveal 3D Fermi surface with unusual interlayer coupling strength in p-SnSe, in which individual monolayers are interwoven by peculiar point dislocation defects. The fingerprinting pudding-mould multivalley band structure is well reserved in bismuth-doped n-type SnSe, which suggest the feasibility of an all-SnSe functioning device.
Speaker: Prof. Yi Zheng (Zhejiang University) -
17:00
Elemental 2D Materials Beyond Graphene 30m
Two-dimensional (2D) materials, which possess atomic or molecular thickness and infinite planar lengths, are regarded as a novel family of materials that have a great potential to transform modern electronics due to their unique nanostructures and electronic states, especially since the discovery of graphene, which possesses amazing functionalities such as high electron mobility and the quantum Hall effect at room temperature. Silicene, germanene, blue phosphorene, new allotropes of silicon, germanium and phosphorous, in 2D one-atom-thick honeycomb structures, could have the potential for promising applications in electronics, photonics, and the other related areas because they not only demonstrates essentially the same electronic properties as graphene, such as linear dispersion of the electron band and high Fermi velocity, but they also possess an energy gap at the Dirac point, stronger spin-orbital coupling (SOC) and inherent compatibility with the current semiconductor industry.
In this talk, I will review our recent work on silicene, germanene, and blue phosphorene. By molecular beam epitaxial deposition, we successfully synthesized large-scale silicene, germanene and blue phosphorene layers on various substrates. The atomic honeycomb structures have been clearly demonstrated by scanning tunneling microscopy (STM). Their phonon properties and distinct electron-phonon coupling effects have been revealed by in-situ Raman spectroscopy. Electronic structures of silicene, germanene and blue phosphorene were demonstrated by scanning tunneling spectroscopy (STS) and angle-revolved photoemission spectroscopy (ARPES). The electronic dispersion, band gap, Fermi velocity, and surface reactive sites at the nano scale and atomic scale on the surfaces of these 2D elemental materials have been studied in details. We also successfully tuned their electronic properties by physical and chemical modulations.Speaker: Dr Yi Du (University of Wollongong)
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Speaker Sessions and Seminars: Nanometer Scale Science & Technology - 2
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Growth and fabrication of molybdenum disulfide devices 30m
The two-dimensional layered material MoS2 is the most common transition metal dichalcogenide. The bulk MoS2 is a semiconductor material with an indirect energy gap (about 1.3 eV) with strong sulfur and molybdenum metal in the plane of the monolayer valence bond function, and there is a very weak Van der Waals force between layers. The monolayer MoS2 has a direct energy gap (about 1.9 eV) and an N-type semiconductor material with strong light emission characteristics, high planar electron mobility and tough mechanical properties, making it applicable applies to transistors, gas sensing detector, photodetector, battery, optoelectronic components. In the past, our laboratory successfully used CVD method to grow graphene and molybdenum disulfide films, combined with the hyper-spectral imaging for the optical properties detection of a few layers of thin film. On the other hand, we also have been successfully fabricated some nanostructures of cuprous oxide and zinc oxide. These nanostructures are made of anodized aluminum and two-beam interference technology. We expect to combine two-dimensional materials and semiconductor device fabrication into biochip through the use of biochips. Using biosensors based on semiconductor material synthesis and micro-nanostructure technology, we hope to develop a low-cost and fast response time, simultaneous detection of biosensors simple program. Recent studies have found that the change of surface stress of transition metal dichalcogenide will change its optical properties such as energy gap, absorption spectrum, even the electron mobility and induced magnetic force. The changes of these properties will enhance the optoelectronic performances of the transition metal dichalcogenide device and material properties. In this study, we will design the best transition metal dichalcogenide devices based on the previous research results. We will apply these devices to biological, gas, and photoelectric sensors and discuss the relationship between the photoelectric characteristics and stress distribution of various devices, and through the deep learning technology to enhance the photoelectric efficiency of devices.
Speaker: Prof. Wang Hsiang-Chen (National Chung Cheng University)
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Speaker Sessions and Seminars: Renewable Energy Technologies
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Nano- and microfabrication technologies for photovoltaic and supercapacitor device applications 45m
Over the last decades, nano- and microfabrication technologies of semiconductors have received considerable attraction for energy and optoelectronic device applications. Various fabrication techniques such as thermal dewetting, anodization, laser interference lithography, etc., followed by dry etching as well as glancing angle deposition and material growth/synthesis have been employed to create the nano- and microstructures. The fabrication technologies were developed to make something better and cheaper for facile scale-up process, which is easily adaptable to industrial applications. The nano- and microstructures are formed by a combination of several fabrication technologies. Their size and height can be controlled by changing the process parameters. Recently, energy-harvesting devices including different types of solar cells for a sustainable energy source as well as sensing devices such biosensors and photodetectors are very important in the fourth industrial revolution. For use of solar cells, coverglass is typically used during the packaging process. The light trapping in packaged solar cells should be enhanced over a wide wavelength range by overcoming some limitations. Still, the design of the structures and the device performance improvement are required. In this talk, we present the formation of nano- and microstructures of metal oxides (ZnO, TiO2, etc.) by different fabrication techniques including glancing angle deposition and thermal dewetting processes, and the structural and optical characteristics are analyzed. The fabricated structures are applied to photovoltaic and sensing devices to improve the device performance.
Speaker: Prof. Jae Su Yu (Kyung Hee University) -
16:45
Performance improvement of perovskite solar cells using novel structure design 30m
In the past decades, many types of the renewable energy, such as solar power, wind power, and biomass energy, are extensively developed owing to the nature fuel has been gradual decrease. Among these renewable energies, solar power is the most promising. The solar power includes Si-based solar cells, III-V solar cells, organic solar cells, and so on. Among them, the organic solar cells have many advantages including easy fabrication in large area, flexibility, lightness, and low cost. For organic solar cells, perovskite is superior to other organic materials in terms of its small absorption bandgap, small exciton binding energy, long exciton lifetime, and large carrier-diffusion length. Consequently, the perovskite solar cells have attracted much attentions.
In this work, multi-layer electron and hole transportation structures were applied to perovskite solar cells to improve the mismatch problem of the carrier mobility. In the perovskite solar cells, the balance electron and hole mobilities reduced the carrier recombination in the cells, which could improve the performance of the cells. The space-charge-limited current (SCLC) method was used to calculate the electron and hole mobilities of the perovskite devices with various electron transportation layers (ETLs) and hole transportation layer (HTL). Compared with the perovskite devices with PC60BM ETL, the current density and PCE of the perovskite solar cells with PC70BM/C70 dual ETLs and PTB7 HTL treated at temperatures of 100 oC were enhanced from18.22 mA/cm2 to 24.11 mA/cm2 and 7.07 % to 14.11 %, respectively. The performance improvement of the perovskite solar cells with PC70BM/C70 dual ETLs and PTB7 HTL treated at temperatures of 100 oC was attributed to that The best carrier mobility balance ratio (μh/μe) of 0.90 for the perovskite devices with PC70BM/C70 dual ETLs and PTB7 HTL treated at temperatures of 100 oC was obtained.
This work was supported from the Ministry of Science and Technology of the Republic of China under contract No. MOST 105-2221-E-006-149-MY2.Speaker: Prof. Hsin-Ying Lee (National Cheng Kung University)
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Conference Gala Dinner Cruise (Sydney Harbour): To Be Confirmed
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Registration
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Plenary: Francesca Iacopi
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Incorporating nanomaterials into semiconductor technologies 1h
Semiconductor technologies are at the basis of most miniaturized systems available to us, whether in the form of microprocessors, or micro and nano -sensors, miniaturised cameras and acoustic systems, etc. Such systems are made of integrated circuits and nanoscale components built in parallel on a semiconductor substrate, following a sequence of hundreds of subtractive, thin -film based processes.
Over several decades, semiconductor technologies could afford to use only a few well -known materials, such as silicon as the semiconductor, silicon dioxide as the insulator, and generally aluminium for the wiring. In more recent times though, this very conservative industry has been forced to introduce a wide range of new materials to enable the downscaling of feature sizes as dictated by Moore’s Law. Nanotechnology, and specifically nanostructured materials, have already or are being introduced in semiconductor technologies, while striving towards the ultimate miniaturisation. Nevertheless, introducing a new material is anything but a straightforward process, due to the strong constraints by chemical and particle contamination, process compatibility, thermal and mechanical stability, quality, and uniformity requirements of the processes in semiconductor manufacturing, as they dictate yield, performance and reliability of a product.
The bottom -up approach most often needed for the synthesis of nanomaterials, the intrinsically higher variability and other difficulties proper to scaling up their synthesis over large areas, as well as considerations related to the compatibility or materials and processes are only some of the bottlenecks to the incorporation of nanostructured materials in semiconductor technologies. We will review the history of successful and unsuccessful attempts to integrate 1D (nanowires) and 2D (graphene) materials as examples. We will conclude that in order for nanomaterials to be meaningfully incorporated in semiconductor technologies, their synthesis needs to be designed and informed from the start by the requirements and constraints of semiconductor manufacturing.Speaker: Prof. Francesca Iacopi (University of Technology)
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Break 15m
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Speaker Sessions and Seminars: Accelerator / Radiation Sciences & Technology - 1
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What is Brilliant and BRIGHT at the AUstralian Synchrotron 45m
The 3 GeV Australian Synchrotron is one of Australia’s premier research facilities and represents one of the biggest single investments in scientific excellence in the nation’s history. Following its operation on behalf of the State of Victoria, the Australian Synchrotron is now owned and operated as part of the Australian Nuclear Science and Technology Organisation (ANSTO). While the majority of ANSTO’s operations are in Sydney, the Australian Synchrotron is located in the Melbourne suburb of Clayton and is staffed by ~140 scientists, engineers, technicians, and support staff.
The Australian Synchrotron has become an integral part of the Australian and New Zealand research landscape. The facility has now supported over 40,000 user visits to its 10 operational beamlines, resulting in scientific research that has already had a significant and lasting impact. The facility generates more than 500 peer reviewed journal articles annually, with 20% appearing in the world’s leading journals.
Moving to Commonwealth operation has allowed provision of funds to significantly refurbish our existing suite of beamlines and machine systems. This presentation will highlight some of the major development projects currently underway at the Australian Synchrotron, as well as indicate the capabilities and activities of several of the current suite of operational beamlines.
Looking forward, the facility has commenced the next phase of Beamline construction, with the development of eight new beamlines. This expansion of the Australian Synchrotron – called the “BRIGHT” program – will deliver a substantial set of new beamline capabilities to complement the existing excellent instrumentation at the facility.Speaker: Prof. Michael James (ANSTO)
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Speaker Sessions and Seminars: Applied Surface Science - 2
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Epitaxial growth of graphene and 2D heterostructures on SiC for nanoelectronic applications 30m
Future applications of graphene in nanoelectronics will depend critically on the perfect control at the atomic level of its direct growth on semiconducting substrates and on the development of novel approaches to introduce a bandgap while preserving carrier mobility. Thermal decomposition of bulk SiC has proven to be an excellent method to grow transfer-free wafer-scale graphene, with the advantage of being perfectly integrated to the Si microelectronic industry fabrication process. Translating this to SiC/Si substrates is a promising but challenging route to decrease the costs.
In this work we present results on two processes that are expected to lead to semiconducting 2D nanostructures based on graphene.
In the first process narrow SiC mesas, fabricated by patterning SiC/Si substrates using Focused Ion Beam (FIB) are annealed at 1250˚C in UHV. Synchrotron radiation spectroscopy and Scanning Tunnelling Microscopy confirm the presence of free standing graphene on the nanostructures after hydrogen intercalation at 600˚C [1].
In the second process lateral graphene/h-BN heterostructures are grown by topological conversion of epitaxial graphene on bulk SiC, allowing the realization of semiconducting hybrid atomic layers with tunable properties. Boron and Nitrogen replace Carbon upon heated exposure of graphene to ammonia ($NH_3$) and boric acid ($H_3BO_3$) vapors: the concentration of h-BN can be controlled via the reaction time. The substitution of h-BN domains in the epitaxial graphene layer is confirmed by x-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), while Raman spectroscopy confirms that the reaction starts at defects sites.[1] M.Amjadipour, et al., Nanotechnology, 29,145601 (2018)
Speaker: Nunzio Motta (Queensland University of Technology) -
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Lateral graphene/h-BN heterostructures from chemically converted epitaxial graphene on SiC (0001) 15m
Graphene has attracted a great deal of interest due to its remarkable properties, but as a zero-bandgap semimetal its full potential for next generation electronic devices is yet to be realized. Unlocking its potential for future applications in nanoelectronics will depend critically on the development of novel approaches to introducing a bandgap while preserving carrier mobility. In-plane heterostructures of graphene and its insulating analogue, h-BN, have been predicted to allow tuning of the bandgap and carrier mobility according to the carbon concentration [1]. Such hybrid structures have previously been synthesized by CVD on metal foils, and patterned using photolithography/reactive ion etching followed by a second growth step, before transfer onto insulating substrates [2].
In this research lateral graphene/h-BN heterostructures are grown on directly on 6H- and 4H-SiC (0001) by topological conversion of epitaxial graphene. Graphene can be chemically converted to h-BN upon heated exposure to ammonia (NH3) and boric acid (H3BO3) vapors, and the concentration of h-BN can be controlled by limiting the reaction time [3]. By x-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), we observe the substitution of h-BN domains in the epitaxial graphene layer. The reaction nucleates at defects or functionalized carbon atoms which we confirm by Raman spectroscopy. This technique allows the growth of semiconducting hybrid atomic layers with tunable properties directly on a substrate suitable for device fabrication.
[1] Wang, J., et. al., Small 9(8) 1373 (2013)
[2] Liu, Z., et. al., Nat Nanotechnol 8(2) 119 (2013)
[3] Gong, Y., et. al., Nat Commun 5 3193 (2014)Speaker: Jonathan Bradford (Queensland University of Technology)
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Morning Tea 30m
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Speaker Sessions and Seminars: Accelerator / Radiation Sciences & Technology - 2
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Overview of the Neutron Scattering Capabilities at the OPAL Research Reactor 10m
The Australian Centre for Neutron Scattering (ACNS) utilises neutrons from Australia’s multi-purpose research reactor, OPAL, to solve complex research and industrial problems for Australian and international users via merit-based access and user-pays programs. Neutron scattering techniques provide the research community and industry with unique tools to study the structure, dynamics and properties of a range of materials, helping scientists understand why materials have the properties they do, and helping tailor new materials.
An overview of the ACNS neutron scattering capabilities at the OPAL reactor will be given together with a selection of scientific and industry case studies.
Speaker: Dr Jamies Schulz (ANSTO) -
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Neutron Imaging Facility DINGO targetting new fields of research with high resolution upgrade 30m
The new neutron radiography / tomography / imaging instrument DINGO is operational since October 2014 to support research at ANSTO. It is designed for a broad national and international scientific user community and for routine quality control for defence, industrial, cultural heritage and archaeology applications. In the field of industrial application it provides a useful tool for studying cracking and defects in concrete or other structural material. Since being operational we gathered experience in various scientific fields, with industrial applications and commercial customers demanding beam time on DINGO. The measured flux (using gold foil) for an L/D of approximately 500 at HB-2 is 5.3 x 107 [n/cm2s], which is in a similar range to other facilities. A special feature of DINGO is the in-pile collimator position in front of the main shutter at HB-2. The collimator offers two pinholes with a possible L/D of 500 and 1000. A secondary collimator separates the two beams by blocking one and positions another aperture for the other beam. The neutron beam size can be adjusted to the sample size from 50 x 50 mm2 to 200 x 200 mm2 with a resulting pixel size from 10µm to ~100µm. First results on 3D-printed functional ceramics tomography and porosity analysis on carbon fibre object will be preseted.
A further upgrade available begin of next year will deliver a pixel size of 2-3µm wit a custom made lens camera setup in combination with an isotope enriched Gadox scintillation screen. In addition we will present an outlook into a real neutron microscope magnifying the neutron image with magnetic lenses targeting the sub micron area. This new imaging instrument concept is a potential candidate for a second guide hall planned at ANSTO.Speaker: Dr Ulf Garbe (ANSTO)
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Speaker Sessions and Seminars: Applied Surface Science - 3
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Tuning the Electronic Structure of NiO by Li doping for Electrocatalytic Water Oxidation 30m
Earth-abundant transition metal (TM) oxides are excellent materials as electrocatalysts for oxygen evolution reaction (OER). It has been proposed that similar to the d-band theory in metal catalysts, the intrinsic OER activity of TM oxides is strongly linked with their electronic structures, i.e., transition metal cations with an occupation of eg=1 showing a high OER activity. This provides guideline for rational design of electrocatalysts.1 We have synthesized Li doped NiO (LixNi1-xO, x= 0, 0.09, 0.17, 0.33 and 0.5) powders and found the materials show increasing catalytic activity for OER as x increases, with comparable OER activity to that of precious IrO2 when x=0.5. The dependence of structure and electronic properties on composition were systematically investigated using high-resolution X-ray photoemission spectroscopy (XPS) and X-ray absorption (XAS) at synchrotron, and density functional theory (DFT) calculations. NiO is a wide bandgap (Eg=3.6 eV) semiconductor with a nominal charge state of Ni2+ (eg2), while Ni in the other end member Li0.5Ni0.5O has a nominal charge state of Ni3+ (eg1). O-K edge XAS indicates development of unoccupied states at 0.5 eV above the top of valence band (VB) with increasing Li doping. These experimental results supplemented with DFT calculations established a direct correlation between the enhancement of catalytic activity with the change of electronic structure.
[1] J. Suntivich, K. J. May, H. A. Gasteiger, J. B. Goodenough and Y. Shao-Horn, Science 334 (6061), 1383-1385 (2011).Speaker: Prof. Kelvin H.L. Zhang (Xiamen University) -
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Controlling the photocatalytic activity of TiO2 thin films grown by atomic layer deposition 15m
Controlling the photocatalytic activity of TiO2 thin films grown by atomic layer deposition
Titanium dioxide (TiO2) represents a perfect example of a multifunctional metal-oxide semiconductor with applications ranging from microelectronics to photo catalysis or medical device materials [1]. Atomic layer deposition (ALD) is widely regarded as one of the most promising techniques for the growth of thin TiO2 films due to its simplicity, reproducibility, the high conformity of the obtained films and an excellent control of the layer thickness at the angstrom level [2].
One of the factors that often dictates the properties of ALD films, and therefore their possible applications, is the crystallinity of the final film. While amorphous films of TiO2 are preferable if diffusion barriers are required for a particular application, crystalline films with a specific phase are often desired for their specific chemical or electrical properties. In addition, the formation of crystallites in TiO2 films is of great technological interest. For example, TiO2 has been regarded as one of the most promising photo-catalytic materials for environment-protective coatings due to its high photo-catalytic activity, high chemical stability and low toxicity [3].
In the present work, the photocatalytic activities of TiO2 thin films, grown by ALD, were investigated as a function of the grain size and crystal structure. The samples were characterized by scanning electron microscopy, grazing incidence X-ray diffraction, secondary ion mass spectrometry, X-ray photoelectron spectroscopy, atomic force microscopy, and near-edge X-ray absorption fine structure spectroscopy. We show that the crystallinity and the size of crystallites can be controlled over a large range of diameters, from around 70 nm up to 1 μm with five parameters: the type of substrate, the type of Ti precursor, the deposition temperature, the number of ALD cycles (i.e. the film thickness) and the nanometric Al2O3 buffer layers deposited on substrates in the same ALD sequences prior to TiO2 films. The most dramatic increase in size of the plate-like anatase grains, to more than 1 μm in diameter, was obtained on films grown at 250 oC on Si substrate covered with a 10 nm Al2O3 layer.
The photocatalytic activity, determined for each TiO2 film from the degradation of methylene blue under UV irradiation, is more efficient for the anatase phase of TiO2 than for the rutile phase, and increases with the grain size of crystallites. The high photocatalytic activity, combined with the low processing temperatures used in the present study, open a wide range of applications for different substrates coated with ALD TiO2 films, such as polymers or cellulose-based substrates, ranging from packaging materials for food to water or air purification systems.
[1] X. Chen, and S. S. Mao, Chem. Rev. 107, 2891 (2007).
[2] M. Knez et al., Adv. Mater. 19, 3425 (2007).
[3] J. G. Chen, Surf. Sci. Rep. 30, 1 (1997).Speaker: Prof. Mladen Petravic (University of Rijeka, Department of Physics)
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Lunch 1h
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Plenary: Fred Watson
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Dark Secrets of the Universe 1h
Aside from the search for extraterrestrial life, the biggest questions confronting astronomers today relate to two fundamental properties of the Universe. Despite their similar names, dark matter and dark energy have vastly different attributes. The nature of both is unknown, yet together they constitute 95 percent of the Universe’s mass-energy budget. In this talk, astronomer Fred Watson reviews the observational evidence relating to dark matter and dark energy, and highlights some of the work being carried out to understand their origin.
Speaker: Prof. Fred Watson (DIIS)
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Break 15m
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Speaker Sessions and Seminars: Accelerator / Radiation Sciences & Technology - 3
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Micro- and nano-tomography with nanoparticles 30m
The new generation synchrotron and X-ray Free Electron Laser facilities mark an important milestone on the development of x-ray science. Two examples will be presented to illustrate the bright potential of x-rays. The extremely bright hard-x-rays provide a unique opportunity to synthesize metal nanoparticles of high quality with high throughput. On the other hand, the same high brightness x-ray photons enable the phase contrast imaging and transmission x-ray microscopy of unprecedented performance. The nanoparticles synthesized by x-rays and the x-ray characterization already impacted life science by tackle important questions, such as the tumor related micro-angiogenesis. With the capability to characterize quantitative all the structural factor of the microvasculature of complete tumor region or an organ, aided with the innovative use of nanoparticles, we could conclude that the phenotype dependent tumor angiogenesis in mouse glioma models.
Using the excellent performances of the SACLA (RIKEN/HARIMA, Japan) x-ray free electron laser (X-FEL), coherent diffraction imaging (CDI) was successfully implemented to image individual liposome particles in water, with or without inserted doxorubicin nanorods. In spite of the low cross section of the original ingredients, the diffracted intensity of drug-free liposomes was sufficient for spatial reconstruction yielding quantitative structural information. For particles containing doxorubicin, the structural parameters of the nanorods can be extracted from CDI. Furthermore, the measurement of the electron density of the solution enclosed in each liposome provides direct evidence of the incorporation of ammonium sulphate into the nanorods. This is an important test for extending the X-FEL analysis of individual nanoparticles to low cross-section-systems in solution, and also for its potential use to optimize the manufacturing of drug nanocarriers.Speaker: Prof. Yeukuang Hwu (Institute of Physics, Academia Sinica)
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Speaker Sessions and Seminars: Catalytic Materials and Processes - 1
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Rational Design of Nano-Catalysts for Sustainable Chemicals and Fuels: Insights from Theory and Simulation 45m
With the ever increasing consumption of the world’s fossil-fuel resources due to the rapid development of industry, as well as climate change which is mainly induced by a surge in CO2 concentration in the atmosphere, both energy and environmental issues are two key problems facing humanity[1]. Over the last decade there has consequently been a substantial increase in innovative utilization of renewable and environmentally benign energy resources. In particular, with the globally increasing socio-political pressure to reduce CO2 emissions, CO2 has become a promising carbon source with a zero or even negative cost and practically unlimited availability for sustainable chemical manufacturing of hydrocarbon fuels and their derivatives. Central to further advancement in the creation of renewable and benign energy sources and environmental protection, is the breakthrough developments of new nanocatalysts.
In the present talk, an over-view and recent results based on first-principles theory calculations, in synergy with experiment will be presented for several key catalytic reactions. These include, the dry reforming of methane with carbon dioxide over a nickel based composite catalyst, conversion of methane and carbon dioxide to the higher value product chemical acetic acid over metal-exchanged zeolites[2], as well as ammonia synthesis from nitrogen reduction over graphitic carbon nitride[3]. Finally, results will be presented illustrating how theory and computation can aid in the screening of candidate materials for particular desired functionalities.
1 G. A. Olah, G. K. S. Prakash, A. Goeppert, Journal of the American Chemical Society 2011, 133 (33), 12881-12898.
2 P. Zhang, X. Yang, X. Hou, J, Huang, C. Stampfl, to be submitted.
3 H. Liu, P. Wu, H. Li, Z. Chen, X. Zeng, Y. Zhu, Y. Jiang, X. Liao, B. Haynes, J. Ye, C. Stampfl, J. Huang, submitted.Speaker: Prof. Catherine Stampfl (The University of Sydney)
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Afternoon Tea 30m
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Speaker Sessions and Seminars: Accelerator / Radiation Sciences & Technology - 4
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The Present Status of Siam Photon Source and Recent Development of Soft X-ray Beamline 30m
The Siam Photo Source (SPS), one of two light sources in South East Asia, has been operating for more than 10 years serving academic and industrial users in Thailand, and users from International. The machine is 1.20 GeV second generation light source with storage ring of 8 bending magnets and 3 insertion devices (undulator, multipoles wiggler and superconducting wavelength shifter). The additional superconducting multipoles wiggler will be installed in August 2018 for new beamline called “ASEAN Beamline”. The full energy injection mode has been studied to replace 1.0 GeV injection mode. The beamlines themselves are developed to improve the capability and operating performance. The Soft X-ray beamline is the first beamline installed at SPS. Initially, it was sourced by bending magnet, but later it was upgraded to undulator since 2011. This beamline is for PES, Soft-XAS and PEEM techniques with photon energy range from 40eV and 1040eV. The detail of development will be discussed.
Speaker: Pat Photongkam (Synchrotron Light Research Institute (Public Organization))
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Speaker Sessions and Seminars: Catalytic Materials and Processes - 2
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An ex situ near edge X-ray absorption fine structure spectroscopy study of metal phthalocyanine catalysts for CO2 reduction 15m
The electrochemical reduction of CO2 is a process that has attracted considerable attention due to the combined benefits associated with the environmental remediation of CO2 and the production of valuable feedstock materials (e.g. CO) for the production of liquid fuels [1]. We have been studying the use of molecular catalysts such as metal phthalocyanines (MPc) as desirable candidates for CO2-to-CO electrochemical catalysis as they can be tuned to achieve high activity and selectivity over proton reduction. In particular, iron phthalocyanine (FePc) is particularly interesting because the Fe(0) centre can donate electrons in the activation of CO2 molecules and exhibits a relatively low onset potential for CO2 reduction when compared with other metal phthalocyanine systems.
Recently, we observed that the addition and self-assembly of metal-oxide nanoclusters (MOx, where M = Ni or Co) on FePc catalysts can result in improved catalytic performance compared to the neat material [2]. Ex situ near edge X-ray absorption fine structure (NEXAFS) measurements were performed on the catalyst materials as a function of applied potential during CO2 reduction. Remarkably, the NEXAFS investigation revealed that at certain potentials, electrochemical substitution occurs between the active iron centre in FePc with the Ni or Co from the MOx nanoclusters. In this presentation, details of the ex situ NEXAFS investigations will be presented, in addition to transmission electron microscopy, atomic force microscopy and electrochemical results that demonstrate improved electrocatalytic performance.
References:
[1] Wilhelm D., Simbeck A., Karp R., Dickenson R., Fuel Process Technol. 71, 139 (2001).
[2] Cheng Y., Veder J.-P., Thomsen L., Zhao S., Saunders M., Demichelis R., Liu C., De Marco R., Jiang S.P., J Mater. Chem. A 6, 1370 (2018).Speaker: Dr Jean-Pierre Veder (Curtin University) -
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Oxygen Reduction Reaction Activity for Pt/Zr/Pt(111) Model Catalyst Surfaces Prepared by Arc-plasma deposition 15m
Oxygen reduction reaction (ORR) activity enhancement mechanisms of Pt-based alloy (Pt-M) catalysts is a key for developing highly-efficient cathode catalysts for polymer electrolyte fuel cell. In particular, the relation between the outermost structure of the Pt-M catalysts and electrochemical (EC) properties, e.g., ORR activity is a key issue. In this study, ORR activities are investigated for Pt/Zr model catalysts prepared on Pt(111) substrate through alternative arc-plasma depositions (APD) of Pt and Zr nano-meter-thick-layers.
The UHV-APD-EC apparatus is described elsewhere [1]. Nano-meter-thick Pt and Zr layers were alternately deposited onto a clean Pt(111) substrate by the APD method. Structural analysis for the prepared model nano-structures are performed by using in-plane XRD, cross-sectional STEM. For the ORR activity evaluation, the UHV-prepared samples were transferred to an N2-purged glove box without air exposure. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were conducted in N2-purged and O2-saturated 0.1M HClO4 in the glove-box.
Surface strain that estimated by the in-plane XRD depended on the deposition thickness ratios of Pt and Zr layers: tensile strain worked on the topmost Pt(111) shell. Estimated ORR activity enhancement factors vs. clean Pt(111) are determined by the tensile surface strain and chemical effects of the topmost Pt(111) layers induced by underlying Zr.
We wish to acknowledge the NEDO of Japan.
[1] S.Kaneko et al., JPCLett. 8, 5360 (2017).Speaker: Prof. Toshimasa Wadayama (Graduate School of Environmental Studies, Tohoku University) -
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Surface defect engineering in semiconducting (photo)electrocatalyst 15m
Surface and near surface regions play a vital role in the determining catalytic activities of photocatalysts and electrocatalysts. Firstly, catalytic reactions take place on the surface of catalysts, where the adsorption/desorption and charge transfer occur between catalyst and molecular. Secondly, abundant surface mismatches, low coordinated ions or atoms, and defects are prevalent on the surface of a materials, which can strongly alter the electronic properties of catalysts and the adsorption/desorption behaviors of molecular on catalysts. Therefore, effective control of the species, concentration, and distributions of surface defects can modulate surface electronic structure and are of great significance in promoting the catalytic activities. Here, we show several approaches of modifying the electronic structure, and molecule adsorption/desorption behavior of various semiconducting (photo)electrocatalysts through manipulating surface defects. In addition, applications of scanning probe microscopies (SPM) techniques, including scanning tunneling microscope (STM) and atomic force microscope (AFM), in revealing the effects of surface defects on these catalysts are highlighted.
Speaker: Mr Haifeng Feng (University of Wollongong)
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Closing and Awards
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