Characterisation of YBCO/Au/YBCO resistors for HTS Josephson noise thermometry

A crucial component of a resistive SQUID noise thermometer is the shunt resistor, which is required to have a value <0.1 m/spl Omega/. The problems of contact resistance between normal metal and HTS superconducting thin films have up to now hindered the implementation of an HTS resistive SQUID. Suitable Au/YBCO/Au shunt resistors /spl sim/20 /spl mu//spl Omega/ have recently been achieved and their characteristics under cryogenic operating conditions have been measured using the Josephson frequency-voltage relationship.