Spray pyrolytic deposition and characterization of SnS and SnS₂thin films

The spray pyrolysis technique is employed to prepare thin films of SnS on glass substrates and SnS 2 on glass as well as fluorine doped tin oxide (FTO) coated glass substrates. The pyrolysis temperatures of SnS and SnS 2 are 350 °C and 275 °C, respectively. The films are found to be n-type semiconductors. The SnS thin film is amorphous, whereas the SnS 2 shows polycrystalline structure and the calculated average grain size is 115 Å for SnS 2 on glass and 324 Å on the FTO substrate. From an analysis of the high absorption region data a direct-allowed transition at 2.44 eV has been observed for SnS 2 . In the optical investigations of SnS layers an non-direct-allowed transition at 1 eV is revealed. The corresponding absorption coefficients near the fundamental absorption edge are ~2 × 10 4 cm -1 and 4.6 × 10 3 cm -1 for SnS 2 and SnS thin films. The room temperature dark conductivity of SnS is of the order of 10 -3 -1 cm -1 and 10 -4 -10 -3 -1 cm -1 for SnS 2 films. The corresponding photoconductivity values of SnS, SnS 2 on glass and SnS 2 on FTO are ten, four and two times higher than the dark conductivity.