Crystal order in Cu2S thin films obtained by spray pyrolysis

Thin films of Cu2S (chalcocite) were obtained onto TCO (SnO2:F) glass, by Spray Pyrolysis Deposition (SPD). As precursors, aqueous and water:ethanol:glyceryne solutions of copper(II) chloride and thiourea with molar ratio Cu:S = 1:3 have been used. The substrate temperature was maintained at 235 deg C, respectively at 285 deg C. The structural and the morphological characterisation of the films has been carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The deposited Cu2S thin films may have tetragonal or monoclinic crystal structure built around two or three preferred orientation OM planes, the (111) plane being the common one. The porous morphology and smaller crystallite sizes suggest that crystal germination is the limiting step in the films deposition, at 235 deg C, from precursor solution containing water or mixtures of water:ethanol:glycerine solvents. Increasing the substrate temperature at 285 deg C, the deposition of dense films with large crystallites/aggregates is favoured, suggesting that crystal growth is the limiting step when water:alcohol mixtures are used as solvents.