Asymmetrical FIB junctions as components for HTS SFQ circuits

High-temperature superconductor (HTS) Josephson junctions have been formed on asymmetrical V-shape grooves etched by a Ga focused-ion beam (FIB). The asymmetrical groove is made by tilting the substrate during FIB etching. Transmission electron microscopy (TEM) shows a tilted V-shape groove and two clear grain boundaries in the NBCO film. The I-V characteristics of the junctions are controlled by the dose amount of Ga ions and the NdBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (NBCO) film thickness. The inductance of the lines was estimated to be 0.5 pH//spl mu/m for the film thickness of 200 nm for the characteristics of a SQUID fabricated with the asymmetrical FIB junctions.