Surface Band Tuning of Bi2Te3 Topological Insulator Thin Films by Gas Adsorption

The surface band tuning of the topological insulator Bi2Te3 by gas adsorption is investigated on the basis of aba initio pound calculations. It is shown that, with the increase of Te vacancies, the topologically non-trivial surface state which originates from the second quintuple layer coexists with the topologically trivial surface. Molecular dynamics simulation reveals that O-2 and NO2 easily occupy the Te vacancy sites and further bind to the Bi atoms from the second atomic layer. Moreover, the surface band with the Dirac cone is observed. Our results suggest that the topological surface state can be effectively regulated by NO2 and O-2 adsorption.