SOME STRUCTURAL, ELECTRICAL AND OPTICAL PROPERTIES OF VACUUM EVAPORATED CdS THIN FILMS

Abstract

In this work, some structural, electrical and optical properties of thermally evaporated CdS thin films with different deposition parameters were investigated. The stoichiometric films that have thicknesses around 2 mu m were found to be in a polycrystalline state of hexagonal form with a preferred direction of crystallization in (002) plane. The current transport mechanisms of the films have been studied as a function of temperature over the temperature range 100-430 K. Temperature dependent conductivity data indicated that thermionic emmission and Mott's variable range hopping are the dominant transport mechanisms above and below 200 K, respectively. Scattering mechanisms over the specified temperature range were also studied and it was found that neutral impurity scattering was dominant in the low temperature region while ionized impurity scattering takes place in the high temperature region. The absorption spectra showed that the optical band gap of the films were around 2.4 eV which makes these low resistive films suitable as a window layer for solar cell applications.