Title :
Characterization of NbN/AlN/NbN tunnel junctions fabricated without intentional heating
Author :
Iosad, N.N. ; Balashov, D.V. ; Kupriyanov, M.Yu. ; Polyakov, S.N. ; Roddatis, V.V.
Author_Institution :
Inst. of Radioelectron., Acad. of Sci., Moscow, Russia
fDate :
6/1/1997 12:00:00 AM
Abstract :
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.
Keywords :
Josephson effect; X-ray diffraction; aluminium compounds; niobium compounds; sputter deposition; superconducting thin films; transmission electron microscopy; DC magnetron sputtering; Josephson junction; Nb-Al-NbN-AlN-NbN; Nb/Al/NbN electrode; NbN/AlN/NbN tunnel junction; SNEP process; X-ray diffraction; cross-sectional TEM; cubic /spl delta/-NbN film; current density; fabrication; gap voltage; intrinsic stress; phase composition; structure; subgap leakage; surface planarization; transition temperature; Current density; Current measurement; Density measurement; Josephson junctions; Magnetic analysis; Niobium; Temperature; Voltage; X-ray diffraction; X-ray scattering;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
