Cd-composition induced effects on structure, optical and electrical properties of sputtered Zn1−xCdxO films

Zn1−xCdxO films with different Cd contents (0≤x≤1) were successfully deposited on quartz substrates by the direct current reactive magnetron sputtering and post-annealing techniques. It was found that structures, band gaps and electrical properties of the films can be tuned by changing Cd contents x. The Zn1−xCdxO film consists of wurtzite phase with highly (002)-preferred orientation at x from 0 to 0.2, mixture of wurtzite and cubic phases at x=0.5, and cubic phase with highly (200)-preferred orientation at x≥0.8. The band gap decreases from 3.25 eV at x=0 to 2.75 eV at x=0.2 for the wurtzite Zn1−xCdxO, and decreases from 2.52 eV at x=0.8 to 2.42 eV at x=1, which has a little change for cubic Zn1−xCdxO. In addition, Hall measurement results indicate that the influence of Cd content on the conduction behavior of Zn1−xCdxO films is significant. The chemical compositions and the bonding states of Zn1−xCdxO films were examined by X-ray photoelectron spectroscopy analysis.