Influence of substrate temperature on structural and optical properties of ZnCdO thin films deposited by dc magnetron sputtering

Zn1−xCdxO (x=0.2) thin films were deposited on glass substrates at different substrate temperatures (Ts) by the direct current (dc) reactive magnetron sputtering method. The influence of substrate temperature on structural and optical properties was investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), optical absorption spectra and Raman scattering in detail. Results indicated that all the obtained Zn1−xCdxO (x=0.2) thin films were of highly (002)-preferred orientation and possessing the hexagonal wurtzite structure of pure ZnO, the crystalline quality first was improved and then deteriorated as the Ts increased up from 25 °C to 600 °C, when Ts is 550 °C, the film had the best crystalline quality. Meanwhile, the optical band gap of Zn1−xCdxO films was tuned from 2.728 to 2.782 eV, which was attributed to the variation of the compressive stress and the Cd re-evaporation in the films. In addition, the residual stress and defects of films were evaluated from Raman spectroscopy.