Structural and Optical Properties of CdSxTe1-xThin Films Fabricated by Thermal Evaporation

CdSxTe1-x films in the range of ( x=0.9 , 0.8, 0.7 ) about 300 nm thickness have been formed on glass substrates by thermal evaporation . X-ray results showed that the CdTe film was polycrystalline with cubic zinc blend structure and had preferred growth of grains along the (111) crystallographic direction. Also, CdS was polycrystalline with hexagonal wurtzite structure and had preferred growth of grains along (002) crystallographic direction while CdSxTe1-x films studied the phase change with an inversion point related to the x-value . Transmittance and absorbance spectra of the films were measured as a function of wavelength (300-1100) nm . Then the band gap of the films calculated by using absorption spectrum , where the direct optical energy gap for CdTe is 1.48 eV and for CdS is 2.5 eV while the direct optical gap of CdSxTe1-x films be limited to between CdS and CdTe , and varied non-linearly , showing downward with decrease x-value .Also the refractive index (n) of these films are discussed.