Fabrication and Properties of High- $T_{\rm c}$ YBCO Josephson Junction and SQUID With Variable Thickness Bridges by Focused Ion Beam

We have successfully fabricated YBCO Josephson junctions and SQUIDs with variable thickness bridges. The variable-thickness bridges of YBCO thin film were fabricated by photolithography and Focused ion beam mill. The Josephson effects of variable thickness bridges were obtained in a 80 nm-thick-film of high-T
_c
YBa
₂
Cu
₃
O
_y
. The Shapiro steps were observed in single junction in the gigahertz range from 3.02 to 14.64 GHz. The voltage-current and voltage-field characteristics were measured in SQUID magnetometer. The SQUID shows a peak-to-peak voltage swing of 1.5 μV at 70 K. The properties of one junction and SQUID magnetometer have been investigated.