Effect of thermal treatment time on high-performance varistors prepared by hot-dipping oxygen-deficient zinc oxide thin films in bismuth oxide powder

Abstract

Through radio-frequency magnetron sputtering zinc oxide sintered ceramic target, oxygen-deficient zinc oxide (ZnO0.81) thin films with a thickness of roughly 270 nm were deposited. Then, through hot-dipping the as-deposited films in Bi2O3 powder at 400 °C, high-performance varistors were fabricated. The effects of thermal treatment time (20–60 min) on the varistors were explored. After hot-dipping, Bi2O3 could enter into the zinc oxide grain boundaries, constructing the typical double-Schottky barriers of varistors. With extending hot-dipping time, the nonlinear coefficient (α) and varistor voltage (VB) of the fabricated thin film varistors initially increase and then decline. Resultantly, the leakage current (IL) decreases firstly and drops down later. The varistor fabricated by hot-dipping in Bi2O3 at 400 °C for 40 min displays the highest α = 15.1 and VB = 0.0176 V/nm, and the lowest IL = 0.0223 mA/cm2. The present nanoscaled film varistors would find wide applications in low-voltage electrical/electronic devices.