Characteristics of bi-crystal grain boundary junctions with different tilt angles for digital circuit applications

We have characterized bi-crystal grain boundary junctions with various tilt angles, i.e., 24/spl deg/, 30/spl deg/, 36.8/spl deg/, and 45/spl deg/ for digital applications. A simple rapid single-flux-quantum (RSFQ) logic circuit has been fabricated using a single layer high-T/sub c/ superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ (YBCO) thin film structure with 4 bi-crystal grain boundary Josephson junctions. The circuit includes one readout superconducting quantum interference devices (SQUID) and one storage SQUID. We have focussed upon the readout SQUID properties, including J/sub c/, R/sub n/A, and I/sub c/R/sub n/, as a function of the tilt angles of the grain boundary junctions. The 24/spl deg/-tilt grain boundary junctions were the best candidates for the simple digital circuits among the bi-crystal grain boundary junctions of the tilt angle from 24/spl deg/ through 45/spl deg/. The response of the readout SQUID was demonstrated by an input signal through the storage SQUID at 82 K.