Tin Sulphide is a layered compound which retains its structure when deposited as thin films by thermal evaporation. The films were found to have oriented growth with the direction of orientation changing with film thickness. The films morphology was
found to change with orientation. The poor conductivity of the thicker samples made it difficult to make photocunductivity characterisation. However, unlike reported the thinner samples showed photo-sensitivity to be independent of film thickness and grain size with a high persistent photocurrent. With their absorption, photosensitivty, optimum band-gap and traps within the band-gap giving the charge carriers a longer life-time, thin samples of tin sulphide gives adequate scope designing efficient photovoltaics. The refractive index was modeled using Sellmeirs model, while most of the previous studies talk of Wemple-DiDomenico single oscillator model or Cauchys dispersion relation. The Sellmeirs fitting parameters are reported which can be of use in ellipsometric studies.
The parameters influencing the band gap of tin sulphide thin nano-crystalline films have been investigated. Both grain size and lattice parameters are known to influence the band gap. The present study initially investigates each contribution individ
ually. The experimentally determined dependency on lattice parameter is verified by theoretical calculations. We also suggest how to treat the variation of band gap as a two variable problem. The results allow us to show dependency of effective mass (reduced) on lattice unit volume.
