Effect of Substrate Properties on Nanostructure and Optical Properties of CdTe Thin Films

Cadmium telluride (CdTe) nanoparticles were deposited on amorphous glass and crystal quartz as nonconductive films, indium tin oxide and fluorine doped tin oxide as transparent conducting films, and silver as a metal at 100 degrees C under pressure of 2x10(-5)mbar. CdTe thin films prepared by a thickness about 80nm. The results of x-ray diffraction analysis show the grain size of preferential orientation was between 5.48nm and 15.37nm. Also, the preferential orientation changed from (111) for non-conducting substrates to (220) for conducting substrates. The investigation of texture coefficient (T-C) has indicated the deviation of T-C from unity for metals substrates is further than the other substrates. The optical properties of CdTe thin films such as the optical band gap, extinction coefficient and refractive index, real and imaginary parts of dielectric constant were investigated by ultraviolet-visible spectroscopy (UV-Vis) as a function of photon energy in the wavelength range of 600-1600nm. These measurements indicated the increasing of optical band gap by increasing the conductivity of substrates. Scanning electron microscopy analysis used to investigate the morphology of thin films.