Toward a Voltage Standard Using YBa 2 Cu 3 O 7-x Josephson Junction Arrays Fabricated by He-FIB

Recent results with shunted YBa2Cu3O7-xJosephson junctions (JJs) fabricated using direct-writing by helium-focused ion beam (He-FIB) demonstrate that this technology is useful to achieve a YBa2Cu3O7-xvoltage standard. By adding a shunt resistor via a subsequent lift-off step, the$\rm{{\mathit{R}}}_\rm{n}$value and thereby the spread of the JJs can be reduced. These results were achieved with one large shunt across multiple JJs. This study presents different designs of shunt resistors, which allow measuring the JJs individually. The different shunt resistor designs are described and evaluated by comparing measurement results without and with the shunt resistor. These show the desired effect of controlling$\rm{{\mathit{R}}}_\rm{n}$, but also a change in$\rm{{\mathit{I}}}_\rm{c}$is visible. The spread in parameters is investigated both without and with shunt resistors. Shapiro steps at gigahertz frequencies are presented for single JJs. The study concludes with a comparative measurement between a YBa2Cu3O7-xHe-FIB JJ and a Josephson Arbitrary Waveform Synthesizer from PTB Braunschweig, showing a deviation of 0.05% and thus demonstrating its potential applicability.