EFFECT OF SOME SPRAY-PYROLYSIS PARAMETERS ON ELECTRICAL AND OPTICAL-PROPERTIES OF ZNS FILMS

Polycrystalline ZnS films of cubic phase were prepared by spray pyroly sis on amorphous substrate. The films were found to be uniform and to adhere well to the substrate. The effects of deposition time (10-30 mi n) and substrate temperature (300-500-degrees-C) on their electrical a nd optical properties were studied. The resistivity was measured at ro om temperature using the square four-probe method. The dark resistivit y was measured as a function of deposition time and substrate temperat ure. Optical data were recorded in the wavelength range 200-1000 nm. T he effect of deposition time (thickness) on resistivity proved the ass umption that the resistivity decreases as the film grows owing to the increase in crystallinity and preferred orientation. The dark resistiv ity increased as the substrate temperature increased. This may be owin g to the decrease in film thickness and improvement in stoichiometry o r the decrease in electron density and mobility. Increasing thermal mi smatch is another important factor. A considerable difference in trans mittance was observed for films prepared at different substrate temper atures. The absorption coefficient was measured and then correlated wi th the photon energy to estimate the energy gap, which was about the v alue for the cubic phase with a direct transition.