FUNDAMENTAL OPERATION OF SINGLE-FLUX-QUANTUM CIRCUITS USING COPLANAR-TYPE HIGH-T-C SQUIDS

We have fabricated coplanar type dc SQUIDs using NdBa2Cu3Oy supercondu cting thin films and operated fundamental single-flux-quantum (SFQ) ci rcuits. The Josephson junctions were made by the narrow-focused ion be am irradiation technique. For a 145 mu m wide and 10 mu m long logic S QUID having a critical current of 105 mu A and an inductive parameter (beta(L)) of 28, a store and a restore of the flux quantum have been d emonstrated at temperatures of 4.2-30 K. These operations were perform ed with an input pulsewidth of 5 ns (5 ns was the shortest input pulse width available from our function generating equipment). These result s show experimentally the possibility of high speed operation in all h igh-T-c superconducting digital circuit. (C) 1996 American Institute o f Physics.