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Title: Systematic materials study of NbN and TaN thin films for SNS Josephson junctions.

Abstract

Abstract not provided.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1380085
Report Number(s):
SAND2016-8522C
647030
DOE Contract Number:
AC04-94AL85000
Resource Type:
Conference
Resource Relation:
Conference: Proposed for presentation at the 2016 Applied Superconductivity Conference held September 4-9, 2016 in Denver, CO.
Country of Publication:
United States
Language:
English

Citation Formats

Missert, Nancy A., Brunke, Lyle Brent, Henry, Michael David, Wolfley, Steven L., Howell, Stephen W., Miner, John, and Lewis, Rupert M.. Systematic materials study of NbN and TaN thin films for SNS Josephson junctions.. United States: N. p., 2016. Web.
Missert, Nancy A., Brunke, Lyle Brent, Henry, Michael David, Wolfley, Steven L., Howell, Stephen W., Miner, John, & Lewis, Rupert M.. Systematic materials study of NbN and TaN thin films for SNS Josephson junctions.. United States.
Missert, Nancy A., Brunke, Lyle Brent, Henry, Michael David, Wolfley, Steven L., Howell, Stephen W., Miner, John, and Lewis, Rupert M.. Mon . "Systematic materials study of NbN and TaN thin films for SNS Josephson junctions.". United States. doi:. https://www.osti.gov/servlets/purl/1380085.
@article{osti_1380085,
title = {Systematic materials study of NbN and TaN thin films for SNS Josephson junctions.},
author = {Missert, Nancy A. and Brunke, Lyle Brent and Henry, Michael David and Wolfley, Steven L. and Howell, Stephen W. and Miner, John and Lewis, Rupert M.},
abstractNote = {Abstract not provided.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Aug 01 00:00:00 EDT 2016},
month = {Mon Aug 01 00:00:00 EDT 2016}
}

Conference:
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  • We investigated properties of NbN and Ta xN thin films grown at ambient temperatures on SiO 2/Si substrates by reactive-pulsed laser deposition and reactive magnetron sputtering (MS) as a function of N 2 gas flow. Both techniques produced films with smooth surfaces, where the surface roughness did not depend on the N 2 gas flow during growth. High crystalline quality, (111) oriented NbN films with T c up to 11 K were produced by both techniques for N contents near 50%. The low temperature transport properties of the Ta xN films depended upon both the N 2 partial pressure usedmore » during growth and the film thickness. Furthermore, the root mean square surface roughness of Ta xN films grown by MS increased as the film thickness decreased down to 10 nm.« less
  • Underlayers of MgO as thin as 8.0 nm have been used in the fabrication of NbN/MgO/NbN Josephson tunnel junctions. NbN/MgO/NbN trilayers with and without MgO underlayers were deposited on thermally oxidized Si substrates at 100/sup 0/C using RF magnetron sputtering in a semi-UHV load lock vacuum system. Sputtering parameters were first optimized to produce NbN with T/sub c/ = 14.7 K on SiO/sub c//Si substrates, and then, thin MgO underlayers were used to enhance the T/sub c/ of the trilayers to 15.7 K. X-ray diffraction of NbN films indicates that thin MgO underlayers of 8.0 nm are capable of almostmore » completely removing the NbN (111) diffraction peak found in lower T/sub c/ films and enhancing the NbN (200) peak. MgO underlayers were found to be oriented in the (100) direction when sputtered in an atmosphere of Ar and N/sub 2/ and randomly oriented when sputtered in an Ar alone. The authors present details for the preparation and analysis of NbN and MgO films as well as the fabrication and electrical performance of tunnel junctions with and without MgO underlayers.« less
  • This paper reports on all-NbN Josephson tunnel junctions with sputter-deposited magnesium oxide barriers fabricated using single crystal NbN films for the base electrodes. Fabricated Josephson junctions have shown good tunneling characteristics with large gap voltages (5.6--5.8 mV), narrow gap widths (0.1--0.2 mV, from 30 to 70%), and small subgap leakage currents (V{sub m} = 20--30 mV, measured at 3 mV). The result of a measurement of a subgap structure for a fabricated junction suggested that the excess leakage currents of fabricated junctions are due to multi-particle tunneling through locally thin areas in the MgO barriers.
  • The authors have developed Josphson LSI fabrication technology using NbN/MgO/NbN tunnel junctions. This paper reports on deposition process of the NbN electrode investigated to obtain high uniformity of the electrical properties. The deposition process of the MgO tunnel barrier was investigated to obtain high reproducibility of the Josephson critical current density. The NbN film with high Tc of 15 K was obtained. The reproducibility of the MgO deposition rate was improved. The 10-bit instruction 128-word ROM unit chip was successfully fabricated using the NbN/MgO/NbN junction LSI technology with the 3 {mu}m design rule. The READ operation test was performed formore » a few 10-bit words. The total access time was measured to be 710 ps. The uniformity and the reproducibility of the critical current density in the LSI chip were improved. The application of the NbN/MgO/NbN tunnel junction to the Josephson LSI fabrication technology was demonstrated.« less
  • AlN has been used as a barrier material in large Josephson junctions. The chemical and structural compatibility of AlN with NbN make it possible to fabricate NbN/AlN/NbN junctions by sequential reactive sputtering in a common Ar and N/sub 2/ atmosphere. In a junction with an area of about 1.0 x 1.0 mm/sup 2/, having a transition temperature of 14.5K, the measured I-V and first derivative curves yield a sum gap value of about 3.0 MeV. 9 refs., 3 figs.