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Nano Josephson superconducting tunnel junctions in YBa2Cu3O7–δ directly patterned with a focused helium ion beam

Nature Nanotechnology volume 10, pages 598–602 (2015)Cite this article

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Abstract

Since the discovery of the high-transition-temperature superconductors (HTSs), researchers have explored many methods to fabricate superconducting tunnel junctions from these materials for basic science purposes and applications. HTS circuits operating at liquid-nitrogen temperatures (∼77 K) would significantly reduce power requirements in comparison with those fabricated from conventional superconductors. The difficulty is that the superconducting coherence length is very short and anisotropic in these materials, typically ∼2 nm in the a–b plane and ∼0.2 nm along the c axis. The electrical properties of Josephson junctions are therefore sensitive to chemical variations and structural defects on atomic length scales1. To make multiple uniform HTS junctions, control at the atomic level is required. In this Letter we demonstrate all-HTS Josephson superconducting tunnel junctions created by using a 500-pm-diameter focused beam of helium ions to directly write tunnel barriers into YBa2Cu3O7−δ (YBCO) thin films. We demonstrate the ability to control the barrier properties continuously from conducting to insulating by varying the irradiation dose. This technique could provide a reliable and reproducible pathway for scaling up quantum-mechanical circuits operating at liquid-nitrogen temperatures, as well as an avenue to conduct novel planar superconducting tunnelling studies for basic science.

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Figure 1: Focused helium ion beam Josephson junction fabrication.
Figure 2: Electrical transport measurements for an SNS Josephson junction fabricated using a dose of 2 × 1016 He+ per cm2 and for a SIS Josephson junction fabricated with a dose of 6 × 1016He+ per cm2.
Figure 3: Measurements of the energy gap of the SIS Josephson junction at higher bias currents.

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Acknowledgements

This work was supported by the Office of Science and Office of Basic Energy Sciences of the US Department of Energy (contract no. DEAC02 05CH11231) and by an AFOSR grant (FA9550-07-1-0493). M.M. and B.W. were supported by the UC scholars programme. The authors thank G. Schlenvogt for help with ion implantation simulations, K. Chen and P. Roediger for experimental discussions, J. Wu for help with the BCS fit, and K.D. Derr, B. Goetze and J. Notte for helping with setting up the experiment.

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Authors and Affiliations

  1. Department of Physics, Oxide Nano Electronics Laboratory, University of California San Diego, La Jolla, 92093, California, USA

    Shane A. Cybart, E. Y. Cho, T. J. Wong, Björn H. Wehlin, Meng K. Ma & R. C. Dynes

  2. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, 94720, California, USA

    Shane A. Cybart & R. C. Dynes

  3. Carl Zeiss Microscopy, LLC., One Corporation Way, Peabody, 01960, Massachusetts, USA

    Chuong Huynh

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  1. Shane A. Cybart
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Contributions

S.A.C. conceived the experiment and wrote the manuscript. S.A.C., E.Y.C. and C.H. fabricated the devices. All authors provided technical and scientific insight that contributed to characterization of the devices and interpretation of the results.

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Correspondence to Shane A. Cybart.

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Cybart, S., Cho, E., Wong, T. et al. Nano Josephson superconducting tunnel junctions in YBa2Cu3O7–δ directly patterned with a focused helium ion beam. Nature Nanotech 10, 598–602 (2015). https://doi.org/10.1038/nnano.2015.76

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