First-principles study on electronic and optical properties of sn-doped topological insulator Bi₂Se₃

Electronic structures and optical properties of pure and sn-doped Bi₂Se₃ were investigated by first-principles calculations based on density functional theory (DFT). For Bi_2-xSn_xSe₃ (x = 0, 0.083, 0.167, 0.25), the introduction of Sn induced impurity bands near the Fermi level. Sn@(0,3) configuration with longer sn-Sn distance was more stable for the smallest formation energy. From the charge density result, sn-doped Bi₂Se₃ was the material with covalent and ionic characteristic. There was obvious blue shifting in the dielectric function and ultraviolet absorption edges for sn-doped Bi₂Se₃. The results had implications for the fabrication of sn-doped Bi₂Se₃ optical devices that can be blue-shifted in ultraviolet (UV) region.