Nano Josephson junctions patterned with a focused helium ion beam

We will present Y-Ba-Cu-O nano Josephson junctions directly written with a focused helium ion beam. Junctions with widths as small as 25 nm were created with precise control over junction parameters like resistance and critical current. In some geometries the voltage state resistance of these nano junctions can be made larger than 1kΩ! For typical planar Y-Ba-Cu-O junctions the Stewart-McCumber Parameter β_C=2e*2π/h*I_C*R_N*R_N*C is very small, however, in these devices we demonstrate high β_C, hysteretic current-voltage characteristics by tuning junction resistance and capacitance.