MgB2 Josephson junctions produced by focused helium ion beam irradiation

• Main Authors: L. Kasaei, T. Melbourne, V. Manichev, L. C. Feldman, T. Gustafsson, Ke Chen, X. X. Xi, B. A. Davidson
• Format: Article
• Language: English
• Published: AIP Publishing LLC 2018-07-01
• Series: AIP Advances
• Online Access: http://dx.doi.org/10.1063/1.5030751

Planar magnesium diboride Josephson junctions are fabricated using focused helium ion beam irradiation. A single track of ion irradiation with a 30 kV He+ beam with nominal beam diameter < 0.5 nm is used to create a normal-metal barrier on a MgB2 film deposited by hybrid physical-chemical vapor deposition. Josephson coupling is observed below the critical temperature of the electrodes for a He+ doses between 8x1015/cm2 to 4x1016/cm2. Analysis of the temperature dependence of the normal resistance and critical voltage of the junctions shows highly uniform barriers with nearly ideal resistively-shunted junction behavior for higher-dose junctions, while nonequilibrium effects dominate the properties of lower-dose junctions over most of the temperature range. These results demonstrate that focused helium ion beam irradiation can produce high-quality proximity-coupled MgB2 Josephson junctions with tailorable properties, promising for use in superconducting devices and circuits.