Characterization of superconducting YBaCuO-films by low temperature scanning electron microscopy

Low-temperature scanning electron microscopy has been performed for imaging the spatial distribution of the critical current densityj_c(x,y) and of the critical temperatureT_c(x,y) in polycrystalline superconducting YBaCuO films. Strongly inhomogeneous behavior has been observed, and the spatial resolution limit has been found to be 1–2 m. The local temperature increment in the specimen film caused by the electron beam scanning has been demonstrated experimentally as the underlying mechanism of the imaging principle, and the beam-induced thermal perturbation of the high-T_c film/substrate configuration is discussed in detail. The radiation hardness of the sample films against the electron beam irradiation in our imaging experiments has been evaluated. No radiation damage could be detected up to the maximum applied dose of well above 10²⁰ electrons/cm² for a typical beam energy of 26 keV.