Impedance spectroscopy studies on chemically deposited CdS and PbS polycrystalline films

Room temperature impedance spectroscopy measurements on chemically deposited CdS and PbS films were performed using the ‘sandwich’ geometry. The experimental data for both materials represented by the complex plane diagrams showed two well-defined semicircles. The results were analyzed in terms of the ‘brick-layer’ model, appropriate for polycrystalline materials in which the crystallites and its boundary are well developed. According to this model, the equivalent circuit which best represent the polycrystalline films, consists of two RC circuits connected in series, one representing the grain and the other the grain boundaries. By fitting the spectral response of the equivalent circuit to the impedance measurements, electrical and structural parameters were obtained.