AN INVESTIGATION ON THE GROWTH OF THIN CHALCOPYRITE CUINSE2 FILMS BY SELENIZATION OF CU-IN ALLOYS IN A BOX

The morphological and structural properties of copper-indium alloys se lenized In a box by selenium vapours have been studied by varying the thermal cycle of the selenization process. In the first series of sele nizations, equal metallic precursors were exposed for 30 min to the se lenium vapours at different temperatures in the range 175-405 degrees C. The chalcopyrite CuInSe2 phase was found at temperatures as low as 250 degrees C and as a single phase at T greater than or equal to 375 degrees C. At low temperatures different copper selenides were found, like CuSe, Cu2-xSe and CuSe2, which affected in a different way the co mposition and morphology of the film. Indium loss was detected in the 250-300 degrees C range and was attributed to the evolution in the gas phase of the In2Se species. Short selenization cycles were also used with the purpose of identifying the chemical precursors of CuInSe2. Th e determination of the selenium content in the alloys at different tem peratures allowed us to determine a 7 kcal/mol activation energy for t he kinetics of selenium incorporation. Long selenizations at 450 degre es C allowed us to obtain a large-grained, compact layer of chalcopyri te CuInSe, which could be used for the fabrication of photovoltaic dev ices.