Planar MgB2 Josephson junctions and series arrays via nanolithography and ion damage -: art. no. 012509

We have fabricated planar thin-film MgB2 Josephson junctions and 20-junction series arrays using 200-keV ion implantation and electron-beam lithography. Resistively shunted junction I-V characteristics were observed in the temperature range of 34-38 K. The ac Josephson effect was observed and flat giant Shapiro steps in arrays suggest good junction uniformity with a small spread in junction parameters. The temperature dependence of the critical current suggests that the nature of the interface between the superconductor and normal region can be described using a soft boundary proximity effect coupling model. We believe that the higher operating temperature and close spacing of these junctions make them promising candidates for quantum voltage standards and other devices. (c) 2006 American Institute of Physics.