Tunneling spectroscopy of superconducting MoN and NbTiN grown by atomic layer deposition

Abstract

A tunneling spectroscopy study is presented of superconducting MoN and Nb${}_{0.8}$Ti${}_{0.2}$N thin films grown by atomic layer deposition (ALD). The films exhibited a superconducting gap of 2meV and 2.4meV respectively with a corresponding critical temperature of 11.5K and 13.4K, among the highest reported $T_c$ values achieved by the ALD technique. Tunnel junctions were obtained using a mechanical contact method with a Au tip. While the native oxides of these films provided poor tunnel barriers, high quality tunnel junctions with low zero bias conductance (below $\sim$10%) were obtained using an artificial tunnel barrier of Al${}_2$O${}_3$ on the film's surface grown $\text{ex situ}$ by ALD. We find a large critical current density on the order of $4\times 10^6$A/cm${}^2$ at $T=0.8T_c$ for a 60nm MoN film and demonstrate conformal coating capabilities of ALD onto high aspect ratio geometries. These results suggest the ALD technique offers significant promise for thin film superconducting device applications.

5 pages, 4 figures

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