The structural, electrical and optical properties of copper-indium alloys sulphurised in H2S atmosphere have been studied by varying the thermal cycle of the sulphurisation process. Cu-In alloy prepared by elemental evaporation of copper and indium was used as the precursor for sulphurisation. The chalcopyrite CuInS2 phase was found at sulphurisation temperature as low as 250degreesC and single phase at sulphurisation temperature 350degreesC. At low sulphurisation temperature different binary phases like CuS, Cu2S, InS and In6S7 were found. Short sulphurisation time also results in secondary binary phases. The optimum sulphurisation temperature was 350degreesC for three hours, which resulted in single-phase p-type chalcopyrite CuInS2 films with a band gap of 1.45 eV. The dependence of processing parameters and the Cu/In ratio of the starting precursors on the electrical, optical and structural properties have also been studied. (C) 2003 Elsevier B.V. All rights reserved.