STRUCTURAL AND DEFECT CHARACTERIZATION OF CUINS2 SINGLE-CRYSTALS GROWN UNDER ELEVATED PRESSURES

By using an argon overpressure, large CuInS2 single crystals were produced. Upon modification of the temperature gradient over the melt a change of structural features was induced. Low temperature gradients resulted in the growth of large single crystals, whereas for increased temperature gradients sheet-like material was prepared. The lamellar material cleaved along the (112) planes as revealed by reflection high-energy electron diffraction, and the appearance of Kikuchi lines indicates good crystallinity. Within the limits of X-ray diffraction the material was shown to be single-phase CuInS2. IR measurements were employed for comparison of materials with different structural properties. Possible origins for the new lamellar structure are discussed. Additional information obtained by a new angle-resolved reflection spectroscopy on the defects in CuInS2 single crystals is presented. The method permits the room temperature detection of small variations of the complex dielectric function-epsilon. The variation of epsilon = epsilon-1, + i-epsilon-2 is correlated to the defect centres and their energetic position in the band gap. The defect levels determined from this method are compared with photoluminescence and transmission spectroscopy results.