High-T_c SQUIDs fabricated by inhibiting ion implantation

We have fabricated YBaCuO superconducting quantum interference devices (SQUIDs) using an inhibiting ion implantation method. The devices were patterned by implanting silicon or boron ions through photoresist masks to locally inhibit the conductivity. The implantation was performed at energies of 40-120 keV and doses of 1015-1016 cm-2. The DC SQUIDs consist of step-edge junctions on SrTiO3 substrates. Operational SQUIDs fabricated with this new patterning method were demonstrated at 77 K. Line widths of 2 μm have been achieved and sharp superconducting-normal boundaries were observed. The surface of the patterned device remained planar. © 1996 IOP Publishing Ltd.