Characterization of co-sputtered Cu-In alloy precursors for CuInSe2 thin films fabrication by close-spaced selenization

Abstract

Sputtering technique for Cu-In precursor films fabrication using different Cu and In layer sequences have been widely investigated for CuInSe2 production. But the CuInSe2 films fabricated from these precursors using H2Se or Se vapour selenization mostly exhibited poor microstructural properties. The co-sputtering technique for producing Cu-In alloy films and selenization within a close-spaced graphite box resulting in quality CuInSe2 films was developed. All films were analysed using SEM, EDX, XRD and four-point probe measurements. Alloy films with a broad range of compositions were fabricated and XRD showed mainly In, CuIn2 and Cu11In9 phases which were found to vary in intensities as the composition changes. Different morphological properties were displayed as the alloy composition changes. The selenized CuInSe2 films exhibited different microstructural properties. Very In-rich films yielded the ODC compound with small crystal sizes whilst slightly In-rich or Cu-rich alloys yielded single phase CuInSe2 films with dense crystals and sizes of about 5 mu m. Film resistivities varied from 10(-2)-10(8) Ohm cm. The films had compositions with Cu/In of 0.40-2.3 and Se/(Cu + In) of 0.74-1.35. All CuInSe2 films with the exception of very Cu-rich ones contained high amount of Se (> 50%). (C) 1998 Elsevier Science B.V. All rights reserved.