Low-temperature scanning electron microscopy for low noise studies of high-T-c superconductors

Low-Temperature Scanning Electron Microscopy (LTSEM) has been successfully applied to the investigation of the local superconducting properties of thin films and Josephson junctions as well as to the study of more complex superconducting circuits. Since many superconducting devices and circuits can be operated successfully only in low ambient magnetic fields, we have built a liquid nitrogen cooled low temperature stage with improved magnetic shielding for the temperature range between 77 and 130 K. For effective magnetic shielding we use a superconducting YBa2Cu3O7-delta tube in addition to several Mumetall shields. We established 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.