Superconducting Weak Bonds at Grain Boundaries in MgB₂

M. A. Tarasov^a, E. A. Stepantsov^b, M. Naito^c, A. Tsukada^c, D. Winkler^d,
A. S. Kalabukhov^{d, e}, and M. Yu. Kupriyanov^e

^a Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Moscow, 125009 Russia

^b Institute of Crystallography, Russian Academy of Sciences, Moscow, 119333 Russia

^c Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16,
Naka-cho, Kogenei, Tokyo, 184-8588 Japan

^d Department of Microtechnology and Nanoscience, Chalmers University of Technology, Göteborg, 41296 Sweden

^e Research Institute of Nuclear Physics, Moscow State University, Moscow, 119992 Russia

e-mail: tarasov@hitech.cplire.ru

Received January 5, 2007

Abstract—The possibility of preparing bicrystalline Josephson junctions and bolometers based on supercon-
ducting MgB₂ on specially prepared bicrystalline MgO substrates is investigated. Microbridges 0.85–6.00 m
in width, intersecting the bicrystalline interface, are formed in epitaxial bicrystalline MgB₂ films grown on
these substrates. It is found that annealing of bicrystalline samples in oxygen leads to a systematic decrease in
the critical current, an increase in the temperature width of the superconducting transition region, and to an
improvement of the current–voltage (IV) characteristic, which becomes close in shape to the IV characteristic
of a Josephson junction. The response of such a junction to radiation at a frequency of 110 GHz with an ampli-
tude attaining 0.5 mV is measured.

PACS numbers: 74.45.+c, 74.50.+r

DOI: 10.1134/S106377610709021X

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