LOW-TEMPERATURE SCANNING ELECTRON-MICROSCOPY FOR LOW-NOISE STUDIES OFHIGH-T-C SUPERCONDUCTORS

Low-Temperature Scanning Electron Microscopy (LTSEM) has been successf ully applied to the investigation of the local superconducting propert ies of thin films and Josephson junctions as well as to the study of m ore complex superconducting circuits. Since many superconducting devic es and circuits can be operated successfully only in low ambient magne tic fields, we have built a liquid nitrogen cooled low temperature sta ge with improved magnetic shielding for the temperature range between 77 and 130 K. For effective magnetic shielding we use a superconductin g YBa2Cu3O7-delta tube in addition to several Mumetall shields. We est ablished further improvements such as an in-vacuum motorized x-y-slide , which allows us to shift the sample with a minimum step width of 1.5 mu m. We present first test measurements of the transport properties of a high T-c de SQUID that demonstrate the functionallity of the new stage.