Study on Anodic Oxidation of Metals and Semiconductors by Electroluminescence Measurement

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Measurements of electroluminescence (EL) from metals and semiconductors during anodic oxidation were carried out in order to investigate the relation between EL behaviors, growth processes of anodic oxide films, and their defective structures and to examine the availability of EL phenomena as an in-situ method for characterization of anodic oxide films.EL was observed from p-type Si during anodic oxidation in ethylene glycol solution of KNO_3. It is suggested that the information on trap levels in SiO_2 and electronic strucutre of SiO_2/Si interface is obtained from the EL spectra. The measurement of changes in EL intensity was capable of monitoring the breakdown of SiO_2 film due to Cl^- ions.EL observed from Nb during anodic oxidation in Na_2SO_4 solution depended sensitively on the surface treatments. Particularly, the mechanical polishing of Nb surface with emery papers gave the maximum EL intensity. The surface impurities remaining on the Nb surface such as SiC become EL sources during anodic oxidation of Nb.These results indicate that EL is useful as an in-situ method for characterization of anodic oxide films on metals and semiconductors.