Characterization of CuInS 2 Thin Films Grown by Close-spaced Vapor Sulfurization of Co-sputtered Cu–In Alloy Precursors

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Abstract
Cu–In alloy films were prepared on bare or Mo-coated glass by co-sputtering from Cu and In targets at ambient temperature. The formation of CuInS2 films was accomplished by sulfurization within a graphite container under high S vapor pressure. X-ray diffraction (XRD) analysis of the alloy films showed predominant variation of the phases from In→CuIn2→Cu11In9 as the Cu content in the films increased. The sulfurized In-rich films formed the CuIn5S8 phase that steadily transformed into CuInS2 as film composition changed toward the Cu-rich region. SEM analysis showed different morphologies for the CuIn5S8 and CuInS2 films. Cu-rich films exhibited very dense crystal structures. EDX composition measurements on the films showed Cu/(Cu+In) varying from 0.21 to 0.64 and S/(Cu+In) from 0.80 to 1.36. Resistivities in the range of 2.36 to 1.7×108 Ω·cm were obtained. Studies of the growth mechanism indicated formation of CuIn5S8 as the main secondary phase in both Cu-rich and In-rich films at low temperatures before conversion into CuInS2 at temperatures >400°C.
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