Growth of heteroepitaxial ZnO thin film and ZnO/(Mg,Zn)O nanomultilayer by off-axis rf magnetron sputtering

Abstract

Heteroepitaxial ZnO thin film was deposited on a sapphire (001) substrate using off-axis radio-frequency magnetron sputtering. The crystallinity of the ZnO thin film was affected by deposition pressure, substrate temperature, and postannealing temperature. The low-temperature photoluminescence of heteroepitaxial ZnO thin film grown under optimum conditions of 650 degreesC. 120 W, and 10 mTorr showed strong UV emission at 3.36 eV with a full width at half maximum (FWHM) of 16.0 meV. After annealing in an O-2 ambient at 950 degreesC, the high-resolution x-ray diffraction rocking curve FWHM of the ZnO thin film markedly decreased from 0.38degrees to 0.19degrees although UV emission decreased. These results indicated that a heteroepitaxial ZnO thin film with strong UV emission can be grown by off-axis rf sputtering and that O-2 annealing helps enhance the crystallinity of ZnO thin film which can be used as a buffer layer in ZnO/(Mg,Zn)O multiple quantum well structures. To demonstrate an application of the ZnO thin film, a ZnO/(Mg,Zn)O nanomultilayer was grown on a ZnO-buffered sapphire substrate and its optical properties were measured. (C) 2005 American Vacuum Society.