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

We have characterized bi-crystal grain boundary junctions with various tilt angles, i.e., 24 degrees, 30 degrees, 36.8 degrees, and 45 degrees for dig ital applications. A simple rapid single-flux-quantum (RSFQ) logic circuit has been fabricated using a single layer high-T-c superconducting YBa2Cu3O7 -x (YBCO) thin film structure with 4 bi-crystal grain boundary Josephson ju nctions, The circuit includes one readout superconducting quantum interfere nce devices(SQUID) and one storage SQUID, We have focussed upon the readout SQUID properties, including J(c), R(n)A, and IcRn, as a function of the ti lt angles of the grain boundary junctions, The 24 degrees-tilt grain bounda ry junctions were the best candidates for the simple digital circuits among the bi-crystal grain boundary junctions of the tilt angle from 24 degrees through 45 degrees. The response of the readout SQUID was demonstrated by a n input signal through the storage SQUID at 82 K.