X-Ray Photoelectron and Auger Electron Spectroscopic Study of the CdTe Surface Resulting from Various Surface Pretreatments: Correlation of Photoelectrochemical and Capacitance-Potential Behavior with Surface Chemical Composition

摘要

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 Te/TeO2 layer (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 approx. 0.7 V for p-CdTe. (Author)