CDSE THIN-FILMS - CHEMICAL-DEPOSITION USING N,N-DIMETHYLSELENOUREA AND ION-EXCHANGE REACTIONS TO MODIFY ELECTRICAL-CONDUCTIVITY

Deposition of CdSe thin films from chemical baths containing cadmium citrate or cadmium tartrate complex ions and using N,N-dimethylselenourea as the source of selenide is presented. Good quality thin films of thickness in the 0.1-0.5 mum range were deposited at 24 or 50-degrees-C. The as-prepared films are of poor crystallinity. On annealing in air at 450-degrees-C for 1 h, well-defined diffraction peaks matching with the hexagonal phase of CdSe are observed. These films have electrical conductivities (sigma(dark) approximately 10(-8) OMEGA-1 cm-1 and are only weakly photosensitive. However, the photosensitivity improves to approximately 10(6) on annealing in air at 450-degrees-C. Ion-exchange reactions of the films in dilute HgCl2 solUtiOns lead to sigma(dark) approximately 1 OMEGA-1 cm-1(n-type) with low photosensitivities. Annealing of these films at temperatures > 200-degrees-C leads to a reduction in sigma(dark) while it enhances the photosensitivity. Immersion of the CdSe films in dilute CuCl, solution makes the films P-type, sigma(dark) approximately 0.1 OMEGA-1 cm-1. Annealing of these films at temperatures >200-degrees-C causes degradation of the films. XPS depth profiles of the films are presented to illustrate the ion-exchange reactions.