Effect of pH on the electrochemical deposition of cadmium selenide nanocrystal films

Cadmium selenide (CdSe) nanocrystalline thin films have been electrodeposited on titanium and indium tin oxide substrates in an electrolyte containing CdSO4 and H2SeO3 at pH 2.50 and temperature 298 K. The influence of pH and the substrate on the chemical composition of the films, optical properties and their crystallinity have been discussed. Nearly stoichiometric CdSe nanocrystalline films with larger absorption and smaller grain sizes were obtained from 0.25 MCdSO4+0.25 mM H2SeO3+0.25 M Na2SO4 solution at a pH of 2.5, employing deposition potential −0.70 V vs. saturated calomel electrode (SCE). X-ray diffraction patterns exhibited single-phase, cubic structure of CdSe thin films. Atomic force microscopy results indicated that the films were smooth, compact with particle sizes about 80 nm when deposited at −0.70 V vs. SCE in pH 2.5 solution of 0.25 M CdSO4+0.25 mM H2SeO3+0.25 M Na2SO4.