HIGH-SPATIAL-RESOLUTION RESISTIVITY MAPPING OF LARGE-AREA YBCO FILMS BY A NEAR-FIELD MILLIMETER-WAVE MICROSCOPE

We demonstrate a new millimeter-wave technique for the resistivity map ping of large-area conducting films, namely, a near-field resistivity microscope. The microscope is based on the idea that electromagnetic w aves are transmitted through a narrow resonant slit with high efficien cy. By scanning this slit at fixed height above an inhomogeneous condu cting surface and measuring the intensity and phase of the reflected w ave, the resistivity of this surface may be determined with a 10-100 m u m spatial resolution using 80-GHz radiation. Using this technique, w e map normal-sate resistivity of 1 in x 1 in YBCO films at ambient tem perature. In some films we find inhomogeneities of the normal-state sh eet resistance of the order of 10%-20%.