Studies on cadmium selenide (CdSe) thin films deposited by spray pyrolysis

Cadmium selenide (CdSe) thin films have been deposited onto well cleaned glass substrates at different substrate temperatures by spray pyrolysis. Aqueous solutions containing precursors of Cd and Se have been used to obtain good quality films. The as-deposited films are characterized for structural, morphological, optical, electrical and thermo electrical properties. X-ray diffraction (XRD) studies reveal that the films are polycrystalline in nature with hexagonal crystal structure. SEM studies reveal that the grains are uniform with uneven spherically shaped, distributed over the entire surface of the substrates. AFM analysis shows uniform deposition of the film over the entire substrate surface. EDAX analysis confirms nearly stoichiometric deposition of the film at 300 degrees C. In optical studies, the transition of the deposited film is found to be a direct allowed with optical energy gaps in the range from 1.74 to 1.87 eV depending on the substrate temperature. The activation energy of the films has been found to be in the range of 0.19-0.27 eV at low temperature and 0.36-0.56 eV at high temperature. Semiconducting behavior has been observed from resistivity measurements. The thermoelectric power measurements reveal that films exhibit n-type conductivity. (C) 2009 Elsevier B.V. All rights reserved.