High quality YBa/sub 2/Cu/sub 3/O/sub 7-δ Josephson junctions and junction arrays fabricated by masked proton beam irradiation damage

Abstract

High quality single Josephson junctions and junction arrays with 10 junctions in series have been fabricated using masked proton beam irradiation damage technology. Monte Carlo simulation of the irradiation damage profile underneath the metal mask has been carried out systematically to guide the metal mask structure design. A high resolution and high aspect ratio metal mask opening was fabricated by focused 30 keV Ga ion beam milling. Various nonconducting oxide buffer layers have been investigated for a Ga contamination free mask fabrication. A contamination free irradiation process and subsequent removal of metal mask after ion irradiation are the keys for the improved properties of junctions fabricated with YBCO.

Large scale two-dimensional arrays of magnesium diboride superconducting quantum interference devices

“…7 In these junctions, the transition temperature (T C ) of a narrow 25-nm region of a superconducting bridge is reduced by irradiation to form a Superconductor-reduced T C -Superconductor-Superconductor junction (S-S 0 -S). [8][9][10][11][12] As a single layer junction technology, device fabrication is relatively easy compared to multi-layer or sandwich junctions and critical current uniformity is excellent. 5,6 The majority of research in ion irradiated nano-junctions has been with the high-T C superconductor YBCO with the exception of a couple of demonstrations using MgB 2 .…”