[en] Spatially resolved resistivity measurements of current transport across individual grain boundaries have been made on superconducting YBa₂Cu_eO₇. These experiments were done by low-temperature scanning electron microscopy with a resolution of 1 to 2 micrometers, and they show directly the limitation of the critical current density caused by grain boundaries in YBa₂Cu₃O₇. Furthermore, complex spatial patterns of the current transport across grain boundaries were observed. These patterns reflect self-excited resonances of the grain boundaries and are closely correlated to the unexplained sub-gap structure in the current-voltage characteristics of polycrystalline YBa₂Cu₃O₇

[en] Low Temperature Scanning Electron Microscopy represents a promising technique for studying the local superconducting properties of high-T/sub c/ films. The spatial and temporal structure of the electron beam induced thermal perturbation of high-T/sub c/ films and the resulting spatial resolution limit is discussed. Typical examples illustrating the new imaging technique are presented

[en] We report the first spatially resolved measurement of the critical transport current density of c-axis oriented epitaxial Y₁Ba₂Cu₃O₇ films on left-angle 100 right-angle SrTiO₃ using low-temperature scanning electron microscopy (LTSEM). The local critical current density, imaged with a spatial resolution of ∼1 μm, has been found to vary considerably in these films. Possible reasons for the observed spatial inhomogeneities are surface imperfections of the substrate and precipitates in the film. The spatial inhomogeneity of the critical current density in epitaxial films might be a reason for differences in the temperature dependences of the critical current density obtained by magnetic and transport measurements