Growth of Nanocrystalline PbS Thin Films by Solid-Vapor Deposition

Abstract

Solidvapor deposition was used to synthesize nanocrystalline PbS thin films on a Si (100) substrate. Lead sulfide (PbS) powder was first prepared and then heated to 1050 °C in a tube furnace. The resulting vapor was carried to the substrate zone by an argon flow. The structure of the nanocrystalline PbS thin films was determined by X-ray diffraction (XRD). The grain size of the PbS thin films and powder was also estimated by XRD. The surface morphology and stoichiometric ratio of these ingots were observed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy. The SEM image revealed that the film had a uniform surface morphology over the entire substrate. The optical absorbance of the deposited films and powder were measured by Fourier-transform infrared spectroscopy. The optical band gap Eg of the samples was calculated using the Tauc formula. The absorption of the thin films was found to be higher than that of the powder and lower for the entire wavenumber range (15005000 nm). The Eg values of the films determined were 3647 nm (0.34 eV), and that of the powder was 3100 nm (0.40 eV).