Optical Properties of Vacuum Evaporated amorphous CdTe Thin Films

In this paper, we have reported the optical properties of vacuum evaporated CdTe thin films. Thin films have been prepared from the polycrystalline powder of CdTe on well-cleaned glass substrate under the vacuum of 10⁻⁶ Torr. The thicknesses of the films were calculated by the quartz crystal monitor (57nm to 575nm). The transmittance characteristics of films were studied by the spectrophotometer. The films were analyzed by an X-ray diffractometer. Lattice constants of the films were determined from the X-ray diffraction pattern using a Nelson-Relay plot. The optical constants (the refractive index n and the absorption constant k) and absorption coefficient α were measured on CdTe thin films in the wavelength range 190nm to 2500 nm. In these, we have observed direct band gap decreases with increasing thickness. The refractive index is found to be decreases of the wavelength of incident photon.