Characterization of NbN/AlN/NbN tunnel junctions fabricated without intentional heating

• Published in: IEEE transactions on applied superconductivity Vol. 7; no. 2; pp. 2805 - 2808
• Main Authors: Iosad, N.N., Balashov, D.V., Kupriyanov, M.Yu, Polyakov, S.N., Roddatis, V.V.
• Format: Journal Article
• Language: English
• Published: IEEE 01.06.1997
• Subjects: Current density; Current measurement; Density measurement; Josephson junctions; Magnetic analysis; Niobium; Temperature; Voltage; X-ray diffraction; X-ray scattering
• DOI: 10.1109/77.621820
• ISSN: 1051-8223

We have fabricated by SNEP process Nb/Al/NbN/AlN/NbN Josephson junctions with the gap voltage V/sub g/=2/spl Delta//e/spl ap/4.0 mV, subgap leakage R/sub sg//R/sub n//spl ap/6.0, current density measured at the gap current rise J/sub g//spl ap/1.5 kA/cm/sup 2/. The (111)-textured NbN with transition temperature T/sub c//spl ap/16 K have been deposited at ambient substrate temperature. Phase composition and structure of the NbN films were investigated by X-ray diffraction analysis (XRD). It was found that the films have a structure close to the cubic /spl delta/-NbN (JCPDS card N38-11556) and the phase composition and intrinsic stress in NbN depend on Ar and N/sub 2/ partial pressure during DC magnetron sputtering. Cross-sectional TEM analysis showed that in-situ deposition of thin Al layer in the base Nb/Al/NbN electrode provides effective planarization of its surface and the result in improvement of tunnel junction parameters.