Characterization of co-sputtered Cu-In alloy precursors for CuInSe 2 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 CuInSe 2 production. But the CuInSe 2 films fabricated from these precursors using H 2Se 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 CuInSe 2 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, CuIn 2 and Cu 11In 9 phases which were found to vary in intensities as the composition changes. Different morphological properties were displayed as the alloy composition changes. The selenized CuInSe 2 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 CuInSe 2 films with dense crystals and sizes of about 5 μm. Film resistivities varied from 10 −2–10 8 Ω cm. The films had compositions with Cu/In of 0.40–2.3 and Se/(Cu+In) of 0.74–1.35. All CuInSe 2 films with the exception of very Cu-rich ones contained high amount of Se (>50%).