Anti-site defect effect on the electronic structure of a Bi₂Te₃ topological insulator

Tuning the Fermi level (E_F) in Bi₂Te₃ topological-insulator (TI) films is demonstrated on controlling the temperature of growth with molecular-beam epitaxy (MBE). Angle-resolved photoemission spectra (ARPES) reveal that E_F of Bi₂Te₃ thin films shifts systematically with the growth temperature (T_g). The key role that a Bi-on-Te(1) (Bi_Te1) antisite defect plays in the electronic structure is identified through extended X-ray-absorption fine-structure (EXAFS) spectra at the Bi L₃-edge. Calculations of electronic structure support the results of fitting the EXAFS, indicating that the variation of E_F is due to the formation and suppression of Bi_Te1 that is tunable with the growth temperature. Our findings provide not only insight into the correlation between the defect structure and electronic properties but also a simple route to control the intrinsic topological surface states, which could be useful for applications in TI-based advanced electronic and spintronic devices.