Journal of the Electrochemical Society, Vol.141, No.2, 558-561, 1994
Preparation of Homogeneous Polycrystalline CuInSe2 Thin-Films by a 2-Step Chemical-Vapor-Transport Process
A two-step chemical-vapor-transport (CVT) process has been developed to prepare homogeneous polycrystalline CuInSe2 thin films and to restrict formation of the second phase. In the two-step CVT process, an electrodeposited Cu/In double layer was heated to 150-degrees-C for 10 min for the first step and then, as the next step, heated to various temperatures in Se vapor. CuInSe2 thin films selenized by the one-step CVT process, where the double layers were heated directly to the selenization temperature, were nonuniform in composition since second phases were formed due to the nonuniform loss of In in the films. The two-step CVT process largely prevented the formation of second phases. High-angle-resolution x-ray diffraction results showed that the grain size of the polycrystalline CuInSe2 films selenized by the two-step CVT process increased as the selenization time and the temperature increased. The characteristic peak at 173 cm-1 in the Raman spectra of the film indicated that the CuInSe2 films were homogeneous in composition. The reason for the restriction of second-phase formation in the two-step CVT process is probably that evaporation of In was blocked by the Se layer deposited on the Cu/In double layer in the first CVT step, which was held at 150-degrees-C for 10 min in Se vapor.