Structural and optical properties of vapor deposited multi-layer CdSe thin films

Structural and optical properties of multi-layer cadmium selenide thin films of various thicknesses were studied. CdSe thin fims were prepared by physical vapor deposition method with alternate layers of cadmium and selenium on unheated glass substrate. The structural investigation performed by X-ray diffraction (XRD) and scanning electron microscopy showed that most of the films were polycrystalline in nature. The stoichiometry of the films determined from EDX results revealed that most of the films did not have equal atomic contents of cadmium and selenium. Refractive indices and absorption coefficient of the film were calculated from the optical transmission spectra. It is found that the size of the crystallites in the polycrystalline films determined from XRD measurements and the optical energy band gap, Eg, calculated from optical measurements depend on the thickness and the composition of the films.