Preparation of CulnSe₂ thin films by rapid thermal processing of Se-containing precursors

Abstract

In this study, CuInSe₂ thin films were prepared by the rapid thermal treatment (RTP) of metallic precursors in a close-spaced graphite container. The thermal diffusion process of selenium into the InSe/Cu/InSe precursor stacks critically influenced the structural properties (i.e., morphological features, formation of crystalline phases and in-depth compositional uniformity) of the films. In cases where pure elemental Se layers were incorporated into the stacks (i.e., InSe/Cu/InSe/Se), RTP treatment yielded compound films with poor structural properties. Single-phase material with uniform and dense surface morphologies was obtained when InSe/Cu/InSe precursors were reacted to an elemental Se atmosphere during RTP treatment. In these cases, single Se pellets were placed in close proximity to the samples in a partially closed graphite container. The container was then rapidly heated in 1 min to 550 °C, followed by a reaction period of 6 min at this temperature. X-ray fluorescence (XRF) K_α1,2 line intensity measurements from these specific samples, after different stages of etching, revealed a relatively high degree of in-depth compositional uniformity. The deposition of this high quality material with a relatively simple and rapid two-stage technique represents an important technological advantage.