Recent studies have shown that the critical currents of several metallic
superconducting nanowires and Dayem bridges can be locally tuned using a gate
voltage {V_g}. Here, we report a gate-tunable Josephson junction structure
constructed from a three-dimensional (3D) niobium nano-bridge junction (NBJ)
with a voltage gate on top. Measurements up to 6 K showed that the critical
current of this structure can be tuned to zero by increasing {V_g}. The
critical gate voltage Vgc was reduced to 16 V and may possibly be reduced
further by reducing the thickness of the insulation layer between the gate and
the NBJ. Furthermore, the flux modulation generated by Josephson interference
of two parallel 3D NBJs can also be tuned using {V_g} in a similar manner.
Therefore, we believe that this gate-tunable Josephson junction structure is
promising for superconducting circuit fabrication at high integration levels.Comment: 15 pages, 5 figure