A low temperature focused ion beam system: Application to in situ processing of high Tc superconducting devices

A modified focused ion beam (FIB) equipment is described. It enables real time imaging by electron scanning microscopy during the FIB milling of cooled samples down to 82 K with liquid N2 cooling, or down to 25 K with liquid He cooling. Experimental results on the patterning of high Tc YBaCuO superconducting thin films are given which show the possibility of ‘‘in situ’’ control of the critical current of micro or nanosuperconducting bridges during the milling. The application of this FIB system to the design of a microthermometer, operating in the pẆ/√Hz range, and of a SQUID, whose Josephson effects correspond to a coherent vortex flow in nanobridges, is detailed.