Influence of post-annealing atmosphere on microstructure, optical and electrical properties of zinc cadmium oxide films deposited by DC and RF magnetron co-sputtering

Zinc cadmium oxide (Zn1−xCdxO) films were deposited on quartz substrates by direct current (DC) and radio frequency (RF) reactive magnetron co-sputtering and the influence of post-annealing atmosphere on their microstructure, optical and electrical properties were investigated by X-ray diffraction (XRD), optical absorbance, photoluminescence (PL) and Hall measurements. Results indicate that the band gap (Eg) of all Zn1−xCdxO films annealed in different atmospheres are smaller than that of the undoped ZnO, the observed shifts in Eg being 0.43, 0.37 and 0.32 eV for the Zn1−xCdxO films annealed in argon, oxygen and vacuum, respectively. Hall measurement results indicate that all Zn1−xCdxO films annealed in different atmospheres show the n-type conduction, but the Zn1−xCdxO film annealed in vacuum has low resistivity and high concentration, which has room-temperature resistivity of 1.59 Ω cm and carrier concentration of 2.07×1017 cm−3. Compared with Zn1−xCdxO films annealed in oxygen and argon, Zn1−xCdxO film annealed in vacuum has the best crystal quality, luminescence and electrical properties. The influencing mechanism of the post-annealing atmosphere on the electrical and optical properties of the Zn1−xCdxO film is discussed.