Enhancement of the light emissions from zinc oxide films by controlling the post-treatment ambient

Abstract

Highly-oriented zinc oxide (ZnO) films were grown on quartz glass substrates by radio frequency magnetron sputtering method. The temperature dependence of the photoluminescence spectra of the ZnO films annealed in argon, argon mixed with 5% hydrogen $({\mathrm{H}}_2/\mathrm{Ar})$ and oxygen ambient, respectively, was investigated from −190 to 600 °C. Results shown that UV light emission was greatly enhanced by annealing the as-grown ZnO film in ${\mathrm{H}}_2/\mathrm{Ar}$ ambient. Meanwhile, strong visible light emission was observed from the ZnO film annealed in oxygen ambient, and intense emissions in both UV and visible region were obtained from the ZnO films annealed in argon ambient. The UV emission from the ZnO films showed a high thermal stability that can be clearly observed up to 400 °C. The effect of the annealing ambient and the photoluminescence temperature dependence are discussed with the relations to the structural defects.