Direct writing of low T-c superconductor-normal metal-superconductor junctions using a focused ion beam

Using a focused ion beam, we have produced superconductor-normal metal-supe rconductor junctions by controllably removing a portion of the top layer of a patterned superconductor-normal metal thin film. The high-quality juncti ons showed Josephson coupling which scaled qualitatively with barrier prope rties and temperature as expected. The largest product of a junction's crit ical current and the normal state resistance measured is 98 mu V at 4.2 K. The method has good reproducibility and could be exploited in a number of s uperconducting electronics applications. (C) 1999 American Institute of Phy sics. [S0003-6951(99)04728-2].