Influence of thermal and compositional variations on conduction mechanisms and localized state density of amorphous Cd50S50-xSex thin films

This work reports the study of dc-electrical conductivity of the amorphous chalcogenide Cd50S50-xSex (30 <= x <= 50 at.%) thin films and its dependent upon the temperature and composition. Thin films were prepared by the thermal evaporation process onto normal glass substrates in a vacuum about 8.2 x 10(-4) Pa. The deposition rate and the film thickness were maintained constant at about 8 nm/s and 200 nm, respectively. X-ray diffraction was used to check the amorphous nature of thin-film samples. The resistance of the film samples has been measured in the temperature range 293 K to 473 K by using the two-point probe technique. DC-electrical conductivity was determined from the resistance measurements. The sheet resistance, the conduction mechanisms, activation energies, Mott parameters, barrier potential energy, trapping state energy and the density of localized states near the Fermi level, were investigated and studied. Obtained electrical data of the ternary Cd-S-Se thin films were investigated and studied in terms of Mott's variable range hopping model. All studied electrical parameters were found to be strongly dependent on the Se-content.