Comparative studies of spray pyrolysis deposited copper sulfide nanostructural thin films on glass and FTO coated glass

Abstract

Cu _x S thin films with different Cu to S molar ratios (0·33 and 0·43) have been deposited by spray pyrolysis method on glass and FTO coated glass substrates using an aqueous solution of copper (II) acetate and thiourea at a substrate temperature of 285°C. The structural, surface morphological, optical and electrical characterizations of the samples were carried out using XRD, FESEM, UV-Vis and PL spectrophotometer and four-probe apparatus, respectively. X-ray diffraction analysis showed that while the layer/glass sample has an individual CuS (covellite) crystalline phase, the layer/FTO sample includes two additional phases of Cu₂S (chalcocite) and Cu_1·8S (digenite) as well. Optical measurements showed that all these materials have a relatively high absorption coefficient (~5 × 10⁴–2·3 × 10⁵ cm^− 1) in the visible region and direct bandgap of the layers was confirmed with the corresponding room temperature PL spectra. With the resistivity measurements at room and higher temperatures (up to 100°C) confirm that all samples are degenerate in nature with high electrical conductivities of ~10³ (Ω.cm)^− 1.