IMAGING OF ELECTRICAL INHOMOGENEITIES IN YBA2CU3O7-X THIN-FILM STRUCTURES BY ROOM-TEMPERATURE LASER-SCANNING MICROSCOPY

Imaging of local electrical inhomogeneities in YBa2Cu3O7-x thin films and grain-boundary junctions was demonstrated at room temperature. The spatial distributions of the voltage response of the samples to the f ocused laser beam were measured with and without bias current through the samples. High-contrast electrical images consisting of 512 x 512 p oints with 8 bit signal resolution and a spatial resolution of up to 1 mum were obtained for all YBa2Cu3O7-x samples under study. The zero-b ias response was shown to reveal the grain-boundary regions in the sam ples and might be explained by thermoelectric effects. The response pr oportional to the current bias was shown to be due to the bolometric e ffect in the material itself and this response can be used to study th e inhomogeneities in grain composition.