Stable Bismuthene on Au/Si(111) Substrate
Bheim M. Llona1*, Hsin-Lei Chou1, Shih-Yu Wu1, Liang-Wei Lan1, Chien-Cheng Kuo1
1Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
* Presenter:Bheim M. Llona
A monolayered bismuth with a buckled honeycomb structure on a Si(111)-α-(√3x√3)-Au-substrate was identified theoretically as a two-dimensional topological insulator (2D TI) [1,2]. However, no experimental evidence has been explicitly shown to materialize this predicted system. Here, we realized a stable bismuth honeycomb structure experimentally on the Au/Si(111) substrate suitable for the characterization of its 2D TI property. The bismuthene on Au/Si(111) was prepared using the technique with modification adapted from ref. [3]. We performed optimization of the parameters to ensure the fabrication of the desired structure be close as possible to the theoretical prediction. It was then followed by an investigation of its signatures as a topological insulator by comparing the topography images, line profiles, I-V curves, density of states (DOS) at the interior, DOS at the periphery and quasiparticle interference (QPI) images. Using the scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS) and Fourier transform-scanning tunneling spectroscopy (FT-STS), we analyzed the interior and the edge state of the bismuthene system. Moreover, the STM was used to characterize the 2D TI bismuthene features including its topography, morphology and real space atomic resolution images of the insulating interior and the conducting edge state. On one hand, the STS was employed to examine both the DOS at the interior and edge state. This approach was to reveal the location of the conduction and the valence bands and to bring out the gapless conducting state along with the Dirac point and Fermi energy. On the other hand, the FT-STS was utilized to show the distinct pattern of energy dispersion relation of the system.

[1] Chuang, F.-C. et al, Nano Lett., 14, 2505−2508 (2014).
[2] Chuang, F.-C. et al, Phys. Rev. B 93, 035429 (2016).
[3] Wu, S-Y. et al, Phys. Rev. B 90, 235407 (2014).

Keywords: Bismuthene, Scanning tunneling microscopy, Scanning tunneling spectroscopy, Fourier transform-scanning tunneling spectroscopy, Two-dimensional insulator