Local characterization of Y-Ba-Cu-O thin films

A high-resolution spatially resolved study of electrical inhomogeneities in high-T_c thin films by Laser Scanning Microscopy has been carried out. A laser beam was focused onto a submicrometer spot on the surface of the thin film microbridge resulting in an increase in its local temperature. Bolometric or thermo-electric effects in the heated region result in a voltage change across the sample that has been measured as a function of the beam position. These two electrical images have been compared with optical images formed by subtracting two conventional images taken with polarized light. The correlation between the three images strongly suggest that interfaces between grains with different twin boundary orientations are more resistive than interfaces between grains with the same twin boundary orientation