Doping nature of Cu in epitaxial topological insulator Bi2Te3 thin films

Using angle-resolved photoemission spectroscopy (ARPES), we investigate the electronic structure of Cu-doped topological insulator Bi2Te3 on Si(111) substrate prepared by molecular beam epitaxy (MBE) to clarify the doping nature of Cu atoms in the films. By systematic studying the structural and electronic properties of the Cu-doped Bi2Te3 films by different doping methods, we find that Cu acts as electron donors when deposited onto the surface of Bi2Te3 films while behave as holes when doped in the process of Bi2Te3 thin film growth. The model of the formation of Cu+, five/seven layer lamella structures and Cu2 −xTe is proposed to explain the different doping mechanisms. The robustness of topological surface states and insensitivity to non-magnetic impurities is indicated.