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

• The ternary Zn1−xCdxO films are obtained by dc reactive magnetron sputtering method.
• The band-gap of Zn−xCdxO was tuned from 3.24 to 2.04 eV by varying x from 0 to 0.5.
• The chemical states of Zn, Cd and O are identified by XPS analysis.
• The band-gap variations were analyzed from the viewpoint of band structure.

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 (0 0 2) preferred orientation. The optical band-gap energies of the Zn1−xCdxO thin films were tuned from 3.24 eV at x = 0 to 2.04 eV 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 (2 0 0) preferred orientation. Correspondingly, the optical band-gap energies of the Zn1−xCdxO thin films decreased from 2.35 eV at x = 0.8 to 2.22 eV 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.

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