Fermi level tuning of Ag-doped Bi(2)Se(3) topological insulator

The temperature dependence of the resistivity (ρ) of Ag-doped Bi(2)Se(3) (Ag(x)Bi(2−x)Se(3)) shows insulating behavior above 35 K, but below 35 K, ρ suddenly decreases with decreasing temperature, in contrast to the metallic behavior for non-doped Bi(2)Se(3) at 1.5–300 K. This significant change in transport properties from metallic behavior clearly shows that the Ag doping of Bi(2)Se(3) can effectively tune the Fermi level downward. The Hall effect measurement shows that carrier is still electron in Ag(x)Bi(2−x)Se(3) and the electron density changes with temperature to reasonably explain the transport properties. Furthermore, the positive gating of Ag(x)Bi(2−x)Se(3) provides metallic behavior that is similar to that of non-doped Bi(2)Se(3), indicating a successful upward tuning of the Fermi level.