SUBMICRON YBA2CU3O7-DELTA GRAIN-BOUNDARY JUNCTION DC SQUIDS

We have fabricated and measured the properties of micron-size single grain boundary junctions and dc superconducting quantum interference devices (SQUIDs). The width of the junctions was varied between 0.25 and 2-mu-m. The junctions were formed in c-axis oriented epitaxial films with a single 24-degrees tilt boundary. They were fabricated using electron beam lithography and ion milling. All of the junctions operate at 77 K The noise properties of SQUIDs made of these junctions have been characterized. They show a significant l/f component which is comparable to published values. However, the white noise level, 3 X 10(-31) J/Hz measured at 77 K, is the lowest ever reported.