CZTS film remains stoichiometric up to 400C.However, the composition of the thin film becomes Zn-poor above 450 C because Zn vaporizes at the elevated temperatures.This leads to the loss of zinc.It can be compensated by spraying Zn and S vapors. But then the sulphur vapours may oxidize.In order to avoid it, CZTS films are taken out of the deposition chamber and are exposed to the atmosphere before sulphurization is performed to grow thin CZTS polycrystalline thin films. Moisture gets adsorbed on the surface and prohibits oxidation of S. The adsorbed moisture later leaves during annealing.This, IN LINE, sulphurization prevents oxidation.JIMBO ET AL employed this method with sputtered CZTS precursor films to prevent oxidation.