Tunable zinc interstitial related defects in ZnMgO and ZnCdO films

Abstract

We report tunable band gap of ZnO thin films grown on quartz substrates by radio frequency magnetron sputtering. The zinc interstitial (Zni) defects in ZnO films were investigated by X-ray diffraction, Raman scattering, Auger spectra, first-principle calculations, and Hall measurement. Undoped ZnO film exhibits an anomalous Raman mode at 275 cm−1. We first report that 275 cm−1 mode also can be observed in ZnO films alloyed with Mg and Cd, whose Raman intensities, interestingly, decrease and increase with increasing Mg and Cd alloying content, respectively. Combined with the previous investigations, it is deduced that 275 cm−1 mode is attributed to Zni related defects, which is demonstrated by our further experiment and theoretical calculation. Consequently, the concentration of Zni related defects in ZnO can be tuned by alloying Mg and Cd impurity, which gives rise to different conductivity in ZnO films. These investigations help to further understand the controversial origin of the additional Raman mode at 275 cm−1 and also the natural n-type conductivity in ZnO.