Ilona Oja

Composition of CuInS2 thin films prepared by spray pyrolysis

CuInS 2 films were prepared by spray pyrolysis technique using CuCl 2 , InCl 3 and SC(NH 2 ) 2 as initial chemicals. The content of Cl, O, C and N impurities in sprayed CuInS 2 films were measured by EDS, WDS, RBS and organic elemental analysis. The growth temperatures of 260-280°C result in Cl, C, N content of 8 mass% and the impurity phases contain SCN, CN, NH, SO 4 groups as identified by FTIR. The increase in the growth temperature up to 380°C decreases the concentration of Cl, C, N to 1-2 mass%, concurrently leading to oxidation of inorganic and organic phases resulting in O content of 16.7 at.%. The content of impurities originated from precursors is mainly controlled by the growth temperature and in less extent by the Cu/In ratio in spray solution as Cu-rich solutions result in the films with reduced content of organic residues. Thermal treatments in reducing atmospheres at 450°C improves the crystallinity of the films while annealing in flowing H 2 effectively reduces the content of Cl and O impurities.

Structural and optical characterization of sprayed ZnS thin films

The cost-effective spray pyrolysis technique was applied to prepare ZnS thin films for large-scale applications. Aqueous solutions containing ZnCl2 and SC(NH2)2 were deposited onto glass and n-type Si(100) substrates at 430-600°C. The structure and phase composition were studied by XRD and FTIR, the surface morphology by SEM. The optical properties were determined from the transmittance and reflectance measurements in the UV-visible and near-IR regions. The phase composition, crystallinity, and surface morphology of the films could be controlled by the Zn:S molar ratio in the stock solution and the deposition temperature. Highly (001) oriented ZnS films with wurtzite structure were grown at temperatures above 500°C using the Zn:S molar ratio 1:2 in the solution. The sprayed films had high optical transmittance in a wide spectral range and the refractive index of up to 1.9 at 632.8 nm. It was also found that the sprayed ZnS films are capable of being used as antireflection coatings in Si-based devices.