Structural and surface characterization of cold deposited zinc sulfide thin films

Zinc sulfide thin films with the thickness of about 0.5 µm were deposited using a thermal evaporation system onto oxidized silicon substrates at cold temperature (Tcold = -50°C) and at ambient temperature (Tambient = 25°C). A special substrate holder with a thermoelectric cooler was used to cool the substrates. The crystalline structure and the morphology of the films were investigated by X-Ray Diffraction and atomic force microscopy, respectively. XRD results show that the structure of the cold deposited ZnS thin film was completely amorphous. The ambient deposited ZnS thin film has a mixture of amorphous structure and polycrystalline structure with the preference orientation of (111) plane. The crystallite size of ambient deposited ZnS thin film was about 10 nm as calculated using the Scherrer formula. The AFM analysis revealed that the estimated grain size of cold deposited and ambient deposited ZnS were about 360 nm and 1220 nm, respectively. The surface roughness of the cold deposited ZnS thin film was greater than the surface roughness of the ambient deposited ZnS thin film