Far-infrared investigations of the surface modes in CdS thin films

The properties of Cadmium sulphide (CdS) thin films were investigated by applying atomic force microscopy (AFM) and far-infrared spectroscopy. CdS thin films were prepared using thermal evaporation technique under a base pressure of 2 x 10(-5) torr. The quality of these films was investigated by AFM spectroscopy. We apply far-infrared spectroscopy to investigate the optical properties of CdS thin films, and reveal the existence of a surface optical phonon (SOP) mode at 297 cm(-1). For the first time, the dielectric function of CdS thin film is modeled as a mixture of homogenous spherical inclusions in air by the Maxwell-Garnet formula. In the analysis of the far-infrared reflection spectra, a numerical model for calculating the reflectivity coefficient for a system which includes films and substrates has been applied.