YBA2CU3O7 DIRECT CURRENT-SUPERCONDUCTING QUANTUM INTERFERENCE DEVICESWITH ARTIFICIAL PRBA2CU3O7 BARRIERS ABOVE 77-K

Direct current-superconducting quantum interference devices (dc-SQUIDs ) from YBa2Cu3O7 with PrBa2Cu3O7 barriers and insulating MgO layers th at modulate up to a temperature of 85 K are prepared by laser depositi on with a KrF excimer laser and an ex situ patterning process. In orde r to utilize the longer coherence length of c-axis oriented YBa2Cu3O7 films in the a-b plane, an edge geometry is used for the definition of the Josephson junctions. By the variation of the barrier thickness th e critical current of the junctions can be controlled within close lim its and can be chosen for optimum dc-SQUID performance at a given work ing temperature. At 80 K we find a flux-voltage modulation of 3.4 muV.