Planar superconductor-normal-superconductor Josephson junctions in MgB2

We report the successful creation of planar MgB2 junctions by localized ion damage in thin (100 nm) films of MgB2 on sapphire by milling a 50 nm trench with a focused-ion beam across tracks of widths between 1 and 5 mum. When the depth of the trench is between 70% and 80% of the film thickness, devices show critical currents (I-C) for temperatures below 25 K. The I-C of these devices is strongly modulated by applied microwave radiation and magnetic field. The product of the critical current and normal state resistance (ICRN) is remarkably high, implying a potential for very-high-frequency applications. (C) 2001 American Institute of Physics.