Sub-micron bicrystalline grain boundary junctions were fabricated, for the first time, by using a focused ion beam process. Although this process was considered to be detrimental, due to Ga contamination, high-quality 24° [001] tilt junctions were identified by their RSJ current–voltage characteristics, ICRN products of the order of 104 to 4 x 104A/cm2 at 77K and Fraunhofer-like modulation patterns. No significant degradation was observed after more than 3 months. The critical current density and the characteristic voltage exhibited clear maxima for widths of the order of the Josephson penetration depth. The asymptotic normal resistance exhibited a typical reciprocal width dependence; thus indicating that the focused ion beam process did not increase the grain boundary resistivity of sub-micron junctions.

Sub-Micron YBa2Cu3O7-x Bicrystal Grain Boundary Junctions by Focused Ion Beam. G.Testa, A.Monaco, E.Sarnelli, A.D’Agostino, D.J.Kang, E.J.Tarte, S.H.Mennema, C.Bell, M.G.Blamire: Superconductor Science and Technology, 2004, 17[2], 287-90