Electrical and structural characteristics of spray deposited (ZnO)$_{X}$-(CdO)$_{1 - X}$ thin films

Abstract

(ZnO)$_{X}$(CdO)$_{1 - X}$ thin films were deposited on glass substrates at 300$^{\circ}$C and 400$^{\circ}$C by ultrasonic spray pyrolysis with compositions ranging from CdO to ZnO. The electrical properties were obtained by impedance spectroscopy and Hall Effect measurements. Scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction, were used to study the structural characteristics of the films. Ellipsometry, in addition, was used to confirm the structural characteristics. The films as deposited resulted mainly polycrystalline and dense, depending on the substrate temperature and on their relative composition. All the films showed n-type conductivity and the films with intermediate compositions resulted in a mixture of both phases; CdO and ZnO. Hall Effect measurements showed that the highest conductivity of CdO was close to 1$\times$10$^{3}$ ($\Omega $-cm)$^{ - 1}$, the highest value obtained for CdO, without doping. Impedance spectroscopy confirmed the Hall Effect results, showing that the highly conducting character of CdO influenced dramatically the conductivity of the (ZnO)$_{X}$(CdO)$_{1 - X}$ films. In addition, depending on the substrate temperature and on the relative composition of the films, both, the bulk or grains, as well as the grain boundaries properties limit the conductivity in them.