Electrodeposition of CdTe semiconductor from ammoniacal aqueous solutions

Electrodeposition of CdTe was studied using aqueous ammonia-alkaline electrolytic baths in which CdII- and Te-IV-ions are dissolving as Cd-II(NK3)(4)(2+) and (TeO32-)-O-IV ions, respectively. Cathodic polarization curves of the baths suggest the presence of strong interaction between the CdII- and Te-IV-ions; electrodeposition of tellurium is inhibited by the presence of Cd(NH3)(4)(2+) ions. The interaction makes it possible to electrodeposit CdTe films with stoichiometric composition. Polycrystalline CdTe thin film of about 1 mu m thickness was electrodeposited at 343 K from ammonia-alkaline solutions (pH = 10.7) containing TeO32-(< 20 mmol dm(-3)) and Cd(NH3)(4)(2+) (< 60 mmol dm(-3)) ions. Increasing Cd(NH3)(4)(2+)/TeO32- mole ratio or decreasing total concentration of ammonia/ammonium-ion gave flat and smooth crystalline CdTe deposits at constant cathode potential -0.70 to -0.30 V vs SHE at 343 K.