Stability and Surface Reconstruction of Topological Insulator Bi₂Se₃ on Exposure to Atmosphere

Abstract

The stability of the surface of vacuum-cleaved topological insulator Bi2Se3 single crystals is investigated with high-resolution synchrotron-based photoelectron spectroscopy. While the surface is stable at room temperature in vacuum, a Bi2 layer always forms at the surface of Bi2Se3 upon even brief (5 min) exposure to atmosphere. This is accompanied by a depletion of selenium in the near surface region and a 1.4 eV decrease in work function. The Bi2 surface is found to be stable upon return to ultrahigh vacuum conditions but is unstable with prolonged exposure to air, ultimately resulting in two possible different reconstructed surfaces, explaining previous contradictory results on long-term atmosphere exposure of Bi2Se3.