FABRICATION OF HIGH-TEMPERATURE SUPERCONDUCTOR JOSEPHSON-JUNCTIONS BYFOCUSED ION-BEAM MILLING

We have fabricated high-critical-temperature Josephson junctions using a focused ion beam (FIB) milling to define the gap, in a-axis oriente d YBa2Cu3O7 (YBCO) films. A good quality normal metal/YBCO interface i s obtained by in situ Au deposition. The effect of FIB milling has bee n studied with different milling conditions and the resulting devices exhibit different I-V characteristics, i.e., flux flow or superconduct or/normal/superconductor Josephson junction behavior. The junctions ex hibit Shapiro steps in their I-V characteristics under microwave irrad iation. The critical current and normal resistance product (IcRn) of t he order of 1 mV has been obtained. We also show that there is a volta ge modulation in the superconducting quantum interference devices as a function of an applied magnetic flux up to 80 K. (C) 1997 American Va cuum Society.