Optimization of Zr-Doped ZnO Thin Films Prepared by Sol-Gel Method

Abstract

Semiconductor thin films of Zr-doped ZnO, with Zr concentrations varying from 0 to 5 at%, have been prepared using a sol-gel method. Crystallinity, microstructure, and optical properties affected by Zr concentration were investigated. In this study, Zr-doped ZnO thin films were deposited onto alkali-free glass substrates by spin-coating. The as-deposited films were preheated at 300°C and then annealed at 500°C in air. The experimental results showed that doping ZnO thin films with Zr not only refined the grain size but also increased transmittance and resistivity. Among all the thin films investigated in the present study, the 3 at% Zr-doped ZnO thin film exhibited the best properties with a transmittance of 86.3% and a RMS roughness value of 5.86 nm. In addition, thin-film transistors were fabricated by spin-coating a 3 at% Zr-doped ZnO active channel layer onto a transistor subassembly. These transistors exhibited n-type depletion mode in which threshold voltage and drain current on-to-off ratio were −18.0 V and 9.6×10⁵, respectively.