Phase separation and compositional changes in two-stage processed chalcopyrite thin films

It is generally accepted that selenization of metallic alloys is a promising process to produce low cost. large area CuInSe2, thin films. In addition, it has been widely reported that the reaction kinetics of these processes are rather complex and that material losses (especially In) during the high temperature selenization stages leads to the formation of detrimental copper rich binary phases. In this study, CuInSe2, thin films were prepared by classical two-stage growth processes in which the precursor formation step as well as the reaction conditions were varied. The compositional features of the samples were investigated by X-ray fluorescence (XRF), which revealed no material losses (i.e. Cu and In) in the temperature range of interest for thin film chalcopyrite synthesis. Comparative XRF K-alpha1.2 and L-alpha1 studies, however, revealed a pronounced segregation of metals under specific experimental conditions. Against this background, the commonly reported material losses of two-stage processed films are explained as a measurement artefact of the widely used electron probe microanalysis (EPMA) under the typical measurement conditions for thin films. (C) 2001 Elsevier Science B,V. All rights reserved.