STRUCTURE AND OPTICAL-PROPERTIES OF CUGASE2 THIN-FILMS

Thin films of CuGaSe2 were prepared by electron beam evaporation of pre-reacted material onto Corning glass substrates maintained at 350 to 450°C. The structure of the films were examined by XRD, Scanning and Transmission electron microscopy. The measured grain sizes were 1-2 μm. At Ts < 400°C, XRD data showed secondary phase formation due to excess copper, where as at Ts ≥ 400°C the films were always chalcopyrite with strong (112) preferred orientation. The optical absorption data showed three characteristic energy gaps at 1.66, 1.76 and 2.45 eV, which correspond to fundamental, band splitting and copper 3d level transitions, respectively. The absorption coefficient was found to decrease with the rise of substrate temperature. © 1990.