ESTIMATION OF INDUCTANCE FOR HIGH-T-C DC-SQUIDS IN COPLANAR WAVE-GUIDE

We have investigated the electrical properties of high-T-c dc-SQUID's formed in a coplanar waveguide, and discussed their applicability to s ingle flux quantum (SFQ) circuits, The planar type Josephson junctions were fabricated in NdBa2Cu3Oy (NBCO) superconducting thin films by a narrow-focused ion beam (FIB) irradiation technique. The critical curr ent and normal resistance values of the Josephson junction at 4.2 K we re 115 mu A and 8 Omega respectively, The inductance was estimated by applying a direct injection of the control current into the dc-SQUID l oop and measuring the periodic voltage response, a loop inductance of 47 pH was obtained for a 25 mu m-wide and 20 mu m-long dc-SQUID at 4.2 K. It has been clarified that for a stable operation of SFQ logic cir cuits, a 10 mu m-square dc-SQUID's are required.