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Temperature-dependent Raman investigation of CuInS2 with mixed phases of chalcopyrite and CuAu

Authors

  • Kunjie Wu,

    1. Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
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  • Deliang Wang

    Corresponding author
    1. Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
    2. CAS Key Laboratory of Energy Conversion Materials, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
    • Phone: +86 551 3600450, Fax: +86 551 3606266
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Abstract

CuInS2 thin films with mixed phases of chalcopyrite (CH) and CuAu (CA) were prepared by using sulfurization of co-evaporated Cu[BOND]In alloy films. Detailed temperature-dependent Raman scattering was carried out on the CuInS2 films at temperatures ranging from 83 to 693 K. The temperature dependences of Raman shifts were well fitted by using the Ridley model for both the CH and the CA A1 modes. The Raman frequency softening upon increasing the sample temperature could be well described by the combined contributions of both thermal expansion and three/four-phonon anharmonic processes. Different Raman linewidths broadening behaviors were observed for the CH and CA A1 modes at temperature below ∼400 K. For the CH A1 mode, the fitting using multiple-phonon anharmonic process matched the experimental linewidth data very well, while for the CA A1 mode, the multiple-phonon fitting could only match the experimental linewidth data at high temperature. At low temperature, the unusual temperature-dependent broadening of the CA A1 mode was believed to arise from the phonon scattering at the CH/CA phase boundary, which encompassed the nano-sized CA domains embedded in the CH crystallite. It was found that the intensity ratio between CA A1 and CH A1 modes (I(CA)/I(CH)) was more reliable in assessment of CH crystallinity at different temperature than CH A1 linewidth. According to the temperature dependence of I(CA)/I(CH), it showed that no phase transformation took place during the test.

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