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

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.

Electrical and mechanical properties of tantalum nitride thin films deposited by reactive sputtering

“…The resistivity of the TaN films varied slightly as their thicknesses changed. When R was maintained at 0.5, the resistivity of the TaN films was around 1 mO cm, which matched with the previously reported values [10,14]. As the thickness of the TaN films increased from $50 to $100 nm while R was maintained at 0.5, the resistivity of the films did not change much.…”

“…As the thickness of the TaN films increased from $50 to $100 nm while R was maintained at 0.5, the resistivity of the films did not change much. When R was maintained at 1, the resistivity of the TaN films was between $500 and $5000 mO cm, which was slightly higher than the previously reported values [10,14]. As the thickness of the TaN films increased from $50 to $80 nm while R was maintained at 1, the resistivity of the TaN films decreased from $5000 to $500 mO cm.…”

Exact dynamical mean-field theory of the Falicov-Kimball model

“…Indeed, we find I c R n is maximized on the insulating side of the metal-insulator transition, and the optimization remains for a wide range of temperature (the reduction in I c R n arises mainly from the temperature dependence of R n for a correlated insulator). These results are consistent with experiments performed on junctions made out of NbTiN for the superconductor and Ta x N for the barrier (Kaul et al, 2001). As tantalum is removed from TaN, it creates tantalum vacancies, which are strongly interacting with the conduction electrons and can trap them at the vacancy site.…”

Superconducting tantalum nitride-based normal metal-insulator-superconductor tunnel junctions

“…In its normal state, it has been used as a barrier material in superconductor-normal metalsuperconductor (SNS) Josephson junctions with NbN (Refs. [18][19][20] and NbTiN (Ref. 21) as the superconducting electrode materials.…”