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

Abstract

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.