User Meeting 2014

Stability and Surface Reconstruction of Bi2Se3 on Exposure to Atmosphere

20 Nov 2014, 13:30

30m

Oral Surface Science Surface Science

Speaker

Dr Mark Edmonds (Monash University)

Description

The new class of topological materials including Bi2Se3 offer opportunities to develop next generation electron devices that utilize spin generation and detection without ferromagnetism [1]. However, the fate of the Bi2Se3 surface upon exposure to atmosphere remains unclear. In particular whilst the topology of Bi2Se3 guarantees the presence of a metallic surface, the topological properties of the metallic surface depend on the surface and its reconstruction [2]. Therefore, it is essential to understand the structure of the air-exposed Bi2Se3 surface in order to interpret the properties of any air-exposed Bi2Se3 device. Utilizing high-resolution surface sensitive XPS we reveal that five minute air exposure causes a drastic change to the surface of in-situ cleaved Bi2Se3. An additional component within the Bi 5d core level was observed after exposure that corresponds to the formation of isolated ~0.8 nm thick Bi2 layers at the surface of Bi2Se3 [3]. This Bi2 layer is found to occur across multiple samples and is precipitated rapidly by exposure to atmosphere, while samples left for several days in UHV after in-situ cleaving show no change. This finding offers new avenues to study a 2D TI (Bi2) interfaced with a 3D TI (Bi2Se3) but also has significant consequences in understanding the electronic structure of air-exposed Bi2Se3. [1] Y. Xia, et al., Nature Physics 5, 398 (2009). [2] Q. D. Gibson, et al., Phys. Rev. B 88, 081108(R) (2013). [3] M. T. Edmonds, et al., J. Phys. Chem. C 118, 20413 (2014).