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Insulator interface effects in sputter‐deposited NbN/MgO/NbN (superconductor–insulator–superconductor) tunnel junctions

Thakoor, S. and LeDuc, H. G. and Stern, J. A. and Thakoor, A. P. and Khanna, S. K. (1987) Insulator interface effects in sputter‐deposited NbN/MgO/NbN (superconductor–insulator–superconductor) tunnel junctions. Journal of Vacuum Science and Technology A, 5 (4). pp. 1721-1725. ISSN 0734-2101. doi:10.1116/1.574517.

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All refractory, NbN/MgO/NbN (superconductor–insulator–superconductor) tunnel junctions have been fabricated by in situ sputter deposition. The influence of MgO thickness (0.8–6.0 nm) deposited under different sputtering ambients at various deposition rates on current–voltage (I–V) characteristics of small‐area (30×30 μm) tunnel junctions is studied. The NbN/MgO/NbN trilayer is deposited in situ by dc reactive magnetron (NbN), and rf magnetron (MgO) sputtering, followed by thermal evaporation of a protective Au cap. Subsequent photolithography, reactive ion etching, planarization, and top contact (Pb/Ag) deposition completes the junction structure. Normal resistance of the junctions with MgO deposited in Ar or Ar and N2 mixture shows good exponential dependence on the MgO thickness indicating formation of a pin‐hole‐free uniform barrier layer. Further, a postdeposition in situ oxygen plasma treatment of the MgO layer increases the junction resistance sharply, and reduces the subgap leakage. A possible enrichment of the MgO layer stoichiometry by the oxygen plasma treatment is suggested. A sumgap as high as 5.7 mV is observed for such a junction

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Additional Information:© 1987 American Vacuum Society. Received 5 November 1986; accepted 22 December 1986. This work was carried out by the Jet Propulsion Laboratory, California Institute of Technology, and was supported by the National Aeronautics and Space Administration (NASA) and Strategic Defense Initiative Organization (SDIO) through an interagency agreement with NASA. We benefited greatly from discussions with Dr. John Lambe and Professor Tom Phillips.
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Strategic Defense Initiative Organization (SDIO)UNSPECIFIED
Subject Keywords:Superconducting junctions; fabrication; electrical properties; sputtering; magnetrons; magnesium oxides; niobium nitrides; interfaces; etching; tunnel effect
Issue or Number:4
Classification Code:PACS: 74.50.+r; 85.25.-j; 73.40.Rw
Record Number:CaltechAUTHORS:20120626-093431176
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Official Citation:Insulator interface effects in sputter-deposited NbN/MgO/NbN (superconductor--insulator--superconductor) tunnel junctions S. Thakoor, H. G. Leduc, J. A. Stern, A. P. Thakoor, and S. K. Khanna, J. Vac. Sci. Technol. A 5, 1721 (1987), DOI:10.1116/1.574517
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32083
Deposited On:26 Jun 2012 19:40
Last Modified:09 Nov 2021 20:03

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