INTERFACIAL DIFFUSION OF METAL ATOMS DURING AIR ANNEALING OF CHEMICALLY DEPOSITED ZNS-CUS AND PBS-CUS THIN-FILMS

We report on the interfacial diffusion of metal ions occurring during air annealing of multilayer CuS films (0.15-0.6 mum) deposited on thin coating of ZnS or PbS (almost-equal-to0.06 mum) on glass substrates. All the films are deposited from chemical baths at room temperature. The interfacial diffusion on the metal atoms during the air annealing is illustrated by x-ray photoelectron spectroscopy studies. A multilayer of 0.3 mum thick CuS film deposited over a thin film of ZnS upon annealing at 150-degrees-C shows atomic ratios of Zn to Cu of approximately 0.15 and approximately 0.48 at the surface layers of the samples annealed for 12 and 24 h, respectively. In the case of CuS on PbS film, the corresponding Pb to Cu atomic ratios at the surface layers are 0.43 and 0.83. The optical transmittance spectra and sheet resistance of these multilayer films indicate thermal stabilities superior to that of the CuS-only coatings. Application of the interfacial diffusion process in the production of thermally stable solar control coatings, solar absorber coating, or p-type films for solar cell structures is discussed.