HIGH-QUALITY YBA2CU3O7 JOSEPHSON-JUNCTIONS MADE BY DIRECT ELECTRON-BEAM WRITING

High-T(c) Josephson junctions have been fabricated by direct electron beam writing over YBa2Cu3O7 thin-film microbridges, using scanning transmission electron microscope (STEM) with an accelerating voltage of 80-120 kV. Annealing at 330-380 K increases T(c) and I(c) of the junctions and makes them more stable. In the operating range of a few degrees below T(c), the junctions show 100% magnetic field modulation of the critical current, microwave-induced Shapiro steps oscillating according to the resistively shunted junction (RSJ) model, and RSJ current-voltage characteristics with I(c)R(n) product up to 0.5-0.6 mV at 75 K and 0.3 mV at 77 K.