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

2014    Groll, Nickolas R.; Klug, Jeffrey A.; Cao, Chaoyue; Altin, Serdar; Claus, Helmut; Becker, Nicholas G.; Zasadzinski, John F.; Pellin, Michael J.; Proslier, Thomas

A tunneling spectroscopy study is presented of superconducting MoN and Nb0.8Ti0.2N 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 similar to 10%) were obtained using an artificial tunnel barrier of Al2O3 on the film's surface grown ex situ by ALD. We find a large critical current density on the order of 4 x 10(6) A/cm(2) at T = 0.8T(c) for a 60 nm MoN film and demonstrate conformal coating capabilities of ALD onto high aspect ratio geometries. These results suggest that the ALD technique offers significant promise for thin film superconducting device applications. (C) 2014 AIP Publishing LLC.