Microprobe Photocurrent Investigations and Laser Induced Radiation Effects on TiO2‐Films

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Abstract
A scanning laser system has been set up, which allows microprobe photocurrent measurements and the generation and investigation of localized radiation effects. The laser beam was focused on a spot size of less than 10 μm and the sample could be scanned with a digitally controlled x — y stage in steps of 1 μm. Local photocurrent fluctuations on anodically formed TiO2‐films are quantitatively correlated to the microscopically observed grain structure of the underlying metal. — Moreover, laser irradiation was found to change the colour, the crystallinity and the photoresponse of the oxide film. This is explained by light induced changes of the electric field within the passive film and the Helmholtz layer, which supports an epitaxial oxide formation on top of the already existing film. The influence of light intensity, illumination time and electrode potential is investigated in detail.