Trimming of step-edge junctions for improvement of SQUID performance

Abstract

We have applied an Ar ion beam etching technique to trim the critical current, Ic, and the normal resistance, Rn, of step-edge Josephson junctions which provides a means to optimize SQUID performance. By using this technique, Ic can be reduced by more than one order of magnitude and Rn can be increased to over 10 Ω. Significant improvements in SQUID performance have been demonstrated with this technique. White noise of 80 f T Hz−1/2 was achieved from a trimmed 5 mm dc SQUID that had poor initial performance.