Influence of Sn incorporation on the properties of CuInS2 thin films grown by vacuum evaporation method

Structural, morphological and optical properties of Sn-doped CuInS2 thin films grown by double source thermal evaporation method were studied. Firstly, the films were annealed in vacuum after evaporation from 250 to 500 DDGC for Sn deposition time equal to 3 min. Secondly, the films deposited for several Sn evaporation times were annealed in vacuum after evaporation at 500 DDGC. The X-ray diffraction spectra indicated that polycrystalline Sn-doped CuInS2 films were obtained and no Sn binary or ternary phases are observed for the Sn evaporation times equal to 5 min. Scanning electron microscopy observation revealed the decrease of the surface crystallinity with increasing the Sn evaporation times and the annealing temperatures. The Sn-doped samples after annealing have bandgap energy of 1.42-1.50 eV. Furthermore, we found that the Sn-doped CuInS2 thin films exhibit N-type conductivity after annealing.