Effects of Cd concentration on microstructure and optical properties of the ternary Zn1−xCdxO alloy thin films synthesized by magnetron sputtering

Abstract

The ternary Zn1−xCdxO (0≤x≤1) alloy thin films were deposited on quartz substrate by the direct current (dc) reactive magnetron sputtering method. As x varied from x=0 to 0.5, the Zn1−xCdxO thin films had a hexagonal wurtzite structure of pure ZnO and highly (002) preferred orientation. The optical band-gap energies of the Zn1−xCdxO thin films were tuned from 3.24eV at x=0 to 2.04eV at x=0.5. But for the samples with x≥0.8, the Zn1−xCdxO thin films had a rock–salt structure of pure CdO and highly (200) preferred orientation. Correspondingly, the optical band-gap energies of the Zn1−xCdxO thin films decreased from 2.35eV at x=0.8 to 2.22eV at x=1, which has a little change. The variations of the band-gap energies for the thin films with hexagonal wurtzite structure were analyzed from the viewpoint of band structure.