Halogen adsorption and reaction with Bi${}_2$(Se,Te)${}_3$ and Bi/Bi${}_2$(Se,Te)${}_3$

Abstract

Bi${}_2$Se${}_3$ and Bi${}_2$Te${}_3$, and these same surfaces covered with Bi films, are exposed to Br${}_2$ and Cl${}_2$ in ultra-high vacuum. Low energy electron diffraction (LEED) and low energy ion scattering (LEIS) are used to investigate the surface composition before and after halogen exposure. It is found that Br${}_2$ weakly chemisorbs to the Se- or Te-terminated clean surfaces and light annealing removes the adsorbates restoring the intact surfaces. In contrast, halogens dissociatively adsorb onto surfaces covered with an additional bilayer of Bi, having a p-doping effect. Annealing these halogen-covered surfaces at 130°C causes Bi atoms to be chemically etched away and the surface reverts to a Se- or Te-termination. This work shows how halogen adsorption and reaction can be used to modify the surface termination of such materials.

36 pages, 6 figures, 2 tables