Mts. Nair et al., CDSE THIN-FILMS - CHEMICAL-DEPOSITION USING N,N-DIMETHYLSELENOUREA AND ION-EXCHANGE REACTIONS TO MODIFY ELECTRICAL-CONDUCTIVITY, Journal of the Electrochemical Society, 140(10), 1993, pp. 2987-2994
Deposition of CdSe thin films from chemical baths containing cadmium c
itrate or cadmium tartrate complex ions and using N,N-dimethylselenour
ea 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 ai
r at 450-degrees-C for 1 h, well-defined diffraction peaks matching wi
th the hexagonal phase of CdSe are observed. These films have electric
al conductivities (sigma(dark) approximately 10(-8) OMEGA-1 cm-1 and a
re only weakly photosensitive. However, the photosensitivity improves
to approximately 10(6) on annealing in air at 450-degrees-C. Ion-excha
nge reactions of the films in dilute HgCl2 solUtiOns lead to sigma(dar
k) approximately 1 OMEGA-1 cm-1(n-type) with low photosensitivities. A
nnealing of these films at temperatures > 200-degrees-C leads to a red
uction in sigma(dark) while it enhances the photosensitivity. Immersio
n of the CdSe films in dilute CuCl, solution makes the films P-type, s
igma(dark) approximately 0.1 OMEGA-1 cm-1. Annealing of these films at
temperatures >200-degrees-C causes degradation of the films. XPS dept
h profiles of the films are presented to illustrate the ion-exchange r
eactions.