Hsin-Lei Chou1*, Chia-Hsiu Hsu1, Shih-Yu Wu1, Hsin Lin2, Feng-Chuan Chuang1, Chien-Cheng Kuo1
1Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan
2Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore
* presenting author:Hsin-Lei Chou,
The carbon with the honeycomb structure, i.e. graphene, was predicted as a topological insulator [1,2]. Nevertheless, the spin orbital coupling (SOC) of carbon is insufficient for showing the topological properties [3-5]. One solution is to replace carbon with Bi having the strong SOC [6,7]. However, growing the honeycomb structure is a tough work because the honeycomb is unstable on the substrate. Bi deposited on Si(111), as one of the examples, forms the trimmer instead of the honeycomb [8]. To overcome this problem, we propose the Si(111)-α-√3×√3-Au to be an ideal template to stabilize the Bi honeycomb [9]. In our work, we found the Bi honeycomb formed on the Si(111)-α-√3×√3-Au by the low energy electron diffraction (LEED) and scanning tunneling microscopy (STM). Bi was deposited on Si(111)-α-√3×√3-Au at room temperature and followed with post-annealing at 550 K for 2 min. An ordered structure of Bi was observed, showing the √3×√3 superstructure in LEED. The surface formed the atomic flat area on the surface from observation of STM. After zooming into the atomic resolution, Bi honeycomb was found on the surface. By density functional calculation, we propose a possible atomic model of 2/3 ML Bi on Si(111)-α-√3×√3-Au, which is consistent with the Bi honeycomb observed in the experiment. This indicates that Au trimmers play the role to stabilize the Bi honeycomb.

[1] C. L. Kane et al., Phys. Rev. Lett. 95, 226801 (2005).
[2] C. L. Kane et al., Phys. Rev. Lett. 95, 146802 (2005).
[3] Yoichi Ando. J. Phys. Soc. Jpn. 82, 102001 (2013).
[4] C. L. Kane et al., Reviews of Modern Physics (2010).
[5] Hongki Min et al., Phys. Rev. B, 74, 165310 (2006).
[6] Miao Zhou et al., Proc. Natl. Acad. Sci. USA, 111, 14 378 (2014).
[7] Miao Zhou et al., Sci. Rep. 4, 7102 (2014).
[8] R. H. Miwa et al., J. Phys.: Condens. Matter 15, 2441 (2003).
[9] Feng-Chuan Chuang, Chia-Hsiu Hsu, Hsin-Lei Chou, Christian P. Crisostomo, Zhi-Quan Huang, Shih-Yu Wu, and Chien-Cheng Kuo, Wang-Chi V. Yeh, Hsin Lin and Arun Bansil (Unpublised).

Keywords: topological insulator, honeycomb structure, Bi, scanning tunneling microscope