Detection and characterization of trap centers in ZnO varistor by ICTS

Abstract

The isothermal capacitance transient spectroscopy (ICTS) was applied to ZnO-Bi2O2-MnO2 ternary varistor system. The ICTS signals caused by three trap levels were detected in three temperature ranges. The detected traps, which were calculated from the slope of Arrhenius plots of ln (τ·T2) vs 1000/T, located at 0.19, 0.29, and 0.60 eV below the conduction band edge. The ICTS signals caused by the traps of 0.19 and 0.29 eV had no dependence on the bias voltage, so that the detected levels were referred to the bulk traps. On the other hand, the signal caused by the trap of 0.60 eV was referred to the interface state because the signal had the dependence on the bias voltage.