On the electrical and optical characteristics of CdO thin films

Cadmium Oxide (CdO) thin films (d=0.15 mu m - 0.70 mu m) were deposited by thermal evaporation under vacuum onto glass substrates kept at 300 K and 473 K respectively. Depending on the substrate temperature, films with polycrystalline or amorphous structures were obtained. The influence of substrate temperature and post-deposition heat treatment on the electrical conductivity, a, and optical transmittance in visible region was investigated. An irreversible temperature dependence of a during heating/cooling cycles of as-grown samples was observed. The results are discussed in relation with cadmium excess and the film recystallization during annealing process. The optical energy bandgap (E-g congruent to 2.4 CV) determined from absorption spectra, indicates direct interband transitions.