The nature of the metal-CO interaction and bonding

The surface chemistry and stoichiometry of p- and n-type CdTe photoelectrodes treated with oxidizing and reducing etches have been characterized by x-ray photoelectron and Auger electron spectroscopies. The results of surface analysis have been correlated with the photoelectrochemical and capacitance-potential behavior of the photoelectrodes. “Oxidized” surfaces are covered by a thin Te⁰/TeO₂layer (or a thicker Te° layer, if the etching procedure is slightly altered), resulting in Fermi level pinning: a constant photovoltage is found for a wide range of redox potentials and potential-independent space charge layer capacitance obtains. “Reduced” surfaces closely resemble ion sputtered CdTe in chemical state and stoichiometry, resulting in more nearly “ideal” behavior: the semiconductor/electrolyte interface is rectifying in the dark; capacitance-potential behavior follows the Mott-Schottky equation near flat band conditions; and photovoltage varies with redox potential, from 0 to —0.7 V for /?-CdTe.