Grain Boundary Josephson Junctions Using Y-Ba-Cu-O Films Operative at 77 K

Grain boundary Josephson junctions were fabricated from superconducting oxide Y-Ba-Cu-O films. The junctions were made by a chemical wet etching technique with phosphoric acid (H3PO4) solution. Typical dimensions of the junctions were a width of 4 µm and a length of 20 µm. The junctions showed the so-called bridge-type Josephson effect. Shapiro steps were observed in the I-V curves at a temperature as high as 77 K.