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

Through radio-frequency magnetron sputtering zinc oxide sintered ceramic target, oxygen-deficient zinc oxide (ZnO0.81) thin films with a thickness of roughly 270nm were deposited. Then, through hot-dipping the as-deposited films in Bi2O3 powder at 400 degrees C, high-performance varistors were fabricated. The effects of thermal treatment time (20-60min) 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 () and varistor voltage (V-B) of the fabricated thin film varistors initially increase and then decline. Resultantly, the leakage current (I-L) decreases firstly and drops down later. The varistor fabricated by hot-dipping in Bi2O3 at 400 degrees C for 40min displays the highest =15.1 and V-B=0.0176V/nm, and the lowest I-L=0.0223mA/cm(2). The present nanoscaled film varistors would find wide applications in low-voltage electrical/electronic devices.