OXIDATION OF N-INP AND INDIUM IN THE NEGATIVE POTENTIAL REGION AT PH-5

A study of the oxidation of n-InP in pH 5.0 aqueous media was undertak en to confirm the formation of InPO4 in the negative potential region. The study necessitated the use of the two buffers, acetate and phosph ate, in order to demonstrate phosphate formation. In order to interpre t the voltammograms and XPS results of the n-InP systems, passivation studies of metallic indium were performed in the same buffer systems. Voltammetry and XPS results of indium and n-InP in acetate buffer syst ems depicted the formation of InPO4 (and/or In(PO3)(3)) on InP. Simila r studies in phosphate buffers showed that n-InP does not undergo oxid ation to the phosphate species. AFM images of polarized n-InP indicate d that the formation of InPO4 (In(PO3)(3)) in acetate buffer is due to the oxidation of the exposed InP on the surface of the n-InP electrod es. The polarized n-InP surfaces in phosphate buffer were completely c overed with metallic indium. The surface of n-InP after successive vol tammograms in acetate buffer contained a large amount of In(OH)(3) and was accompanied with greater amounts of phosphate species closer to t he interface.