Investigation of trapping states in a Nb-doped rutile by admittance spectroscopy

Abstract

In order to obtain semiconductivity, rutile crystals have been doped with Nb by means of diffusion. The resulting Nb‐doped rutile crystals have an electrical resistivity ≂80 Ω cm at room temperature. Impedance analysis of a Nb‐doped TiO₂‐Au diode suggests that the measurement frequency must be lower than 10 kHz to detect the capacitance and conductance of the depletion layer. Thus, an admittance spectroscopic method is used to study traps in the diode of the Nb‐doped TiO₂‐Au. Two trap levels, located at 0.24 and 0.37 eV below the bottom of the conduction band, have been detected by this method. The state densities and capture cross sections of these trap levels are also determined.