Adsorption and Diffusion of Atoms of Groups 1, 2 and 13 Elements on Antimony Telluride Surface

The paper presents ab initio calculations of the adsorption and diffusion of atoms of groups 1, 2 and 13 elements on the (0001) surface of antimony telluride (Sb2Te3) topological insulator. It is shown that most of the investigated adatoms possess minimum energy when occupying the face-centered cubic (FCC) hollow site. Exceptions are presented only for beryllium, boron, indium and thallium atoms which adsorb at the hexagonal close-packed (HCP) hollow site. The adatom diffusion on Sb2Te3 (0001) surface occurs in two stages, i.e. adatoms hop from an FCC site to an HCP site and vice versa. For beryllium, boron, indium and thallium atoms the order of these hops is modified because the HCP hollow site is more favorable location in terms of the absorption energy. The energy barriers are determined for hops on Sb2Te3 (0001) surface, and the obtained hop frquencies are used to analytically calculate the diffusion lengths. The diffusion activation temperature is determined, when the adatom passes through the interatomic spacing of 2.5 Å in one minute. It is found that the highest (165 K) activation temperature belongs to beryllium, while the lowest (39 K) corresponds to cesium.