Gas Doping on the Topological Insulator Bi2Se3 Surface

TL;DR

This study uses first-principles calculations to explore how gas molecules like NO2 and O2 can passivate Se vacancies on Bi2Se3 topological insulator surfaces, restoring their electronic properties and suggesting new device applications.

Contribution

It reveals the specific interactions of gas molecules with Se vacancies on Bi2Se3, including NO2 dissociation, providing insights into doping mechanisms and experimental validation strategies.

Findings

NO2 and O2 occupy Se vacancies and restore band structure

NO and H2 do not passivate vacancies effectively

NO2 dissociation explains photon-doping effects

Abstract

Gas molecule doping on the topological insulator Bi2 Se3 surface with existing Se vacancies is investigated using first-principles calculations. Consistent with experiments, NO2 and O2 are found to occupy the Se vacancy sites, remove vacancy-doped electrons and restore the band structure of a perfect surface. In contrast, NO and H2 do not favour passivation of such vacancies. Interestingly we have revealed a NO2 dissociation process that can well explain the speculative introduced "photon-doping" effect reported by recent experiments. Experimental strategies to validate this mechanism are presented. The choice and the effect of different passivators are discussed. This step paves the way for the usage of such materials in device applications utilizing robust topological surface states.