Electrodeposition of CdTe from Acidic Aqueous Solutions Containing Citric Acid

Potentiostatic cathodic electrodeposition of CdTe compound on a gold-plated substrate was studied at 70oC using new acidic aqueous electrolytic baths (pH3.0) containing citric acid. The composition of the deposits was controlled by changing the deposition potential, which depended on the concentrations of Te(IV) and citrate. The stoichiometric CdTe layers obtained were polycrystalline, having a uniform surface morphology without pinholes. In the presence of citrate ions, the solubility of tetravalent tellurium species in the citrate bath at pH3.0 was more than 10mM, which was about one or two orders higher than that in conventional acidic sulfate baths. The increase in the solubility will be accounted for by a complexation between Te(IV) and citrate ions, which has not been reported so far. A set of linear sweep cathodic voltammograms for Te(IV)-citrate baths suggested the presence of the complex.

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