Preparation of covellite and digenite thin films by an intermittent spray pyrolysis deposition method

Intermittent spray pyrolysis of 0.01–0.20 M aqueous solutions of CuCl (dissolved in the presence of 3-fold molar amount of thiourea) onto a heated alkali-free glass substrate in air already at 225–275°C resulted in various thin films of CuS (covellite) and/or Cu1.8S (Cu9S5, digenite). A combination of low pyrolysis temperatures (225–250°C) and low solution concentrations (0.01–0.02 M) has resulted in the formation of thin solid CuS films. At a pyrolysis temperature of 275°C Cu1.8S films have been obtained. The higher concentration range (0.05–0.20 M) has been found favorable for simultaneous formation of Cu1.8S and CuS. In the two-phase layers the crystal growth of CuS has seemed to be limited, whilst the growth of Cu1.8S has been preferentially favored especially on its (0 0 15) lattice plane.