Crystal structure and spectral photosensitivity of thermally evaporated ZnxCd1-xSe thin films

Single layers of ZnxCd1-xSe with various compositions (x = 0.39, 0.52, 0.59, 0.69 and 0.8) were prepared by thermal vacuum evaporation. Consecutive deposition of films from ZnSe and CdSe with equivalent thickness of 0.12, 0.25 or 0.37 nm was applied and the composition was varied by alloying ZnSe and CdSe films with different equivalent thicknesses. Single layers from ZnSe were prepared for comparison. X-ray diffraction, Raman scattering and spectral photocurrent measurements were carried out to get information on the film crystallinity and spectral photosensitivity. It was observed that both binary and ternary films are of cubic structure and nanocrystalline. No pure CdSe or ZnSe phases were found in the ZnxCd1-xSe films but the Raman data indicated that Cd-enriched nanosized regions can exist. The Raman scattering and spectral photocurrent results showed that the optical band gap of the ternary films gradually increased with increasing x and achieved a value of around 2.4 eV for the films with x = 0.8.