Determination of the structural and optical characteristics of Cu$_2$ZnSnS$_4$ semiconductor thin films

The results of X-ray diffraction and optical studies of Cu$_2$ZnSnS$_4$ films produced by the flash evaporation of binary sulfide compounds under different technological conditions is reported. It is shown that it is possible to produce Cu$_2$ZnSnS$_4$ films, rather perfect in structural and optical respects, by choosing the optimal annealing temperatures at different Ar vapor pressures. The lattice parameters of the compounds are determined. The systematic shift in the photoluminescence bands under variations in the excitation level is established. It is found that the characteristics of the bands depend to a large extent on the annealing temperature, the Ar pressure during thermal treatment, and the resultant stoichiometry composition of the samples. It is shown that Raman studies and luminescence measurements can be used to assess the quality of the synthesized Cu$_2$ZnSnS$_4$ films and to obtain data on the energy structure of defects in the band gap.