Internally shunted sputtered NbN Josephson junctions with a TaNx barrier for nonlatching logic applications

TLDR

TaNx film resistivity can be tuned from a few hundred micro‑ohms to a few hundred milliohms by adjusting N₂ pressure during reactive sputtering. The authors aim to grow, fabricate, and characterize NbN internally shunted Josephson junctions incorporating a TaNx barrier. They fabricated the junctions by reactive sputtering, varied the TaNx barrier thickness, and performed device characterization including IcRn measurements. The junctions exhibited a coherence length of 5 nm, and by tuning barrier thickness they achieved IcRn values exceeding 500 µV up to 8.3 K, making them suitable for single‑flux‑quantum digital circuits.

Abstract

We report on the growth, fabrication, and device characterization of NbN internally shunted Josephson junctions with a TaNx barrier. The resistivity of TaNx films could be varied from a few hundred micro-ohms to a few hundred milliohms by increasing the N2 pressure during reactive sputtering. The temperature dependence of IcRn of the junctions with ∼13 mΩ cm barrier resistivity was measured for various barrier thicknesses. The coherence length of the barrier was determined to be 5 nm. By adjusting the barrier thickness, IcRn values >500 μV were observed up to 8.3 K, with Ic and Rn of magnitudes that are suitable for single-flux-quantum digital circuits.