High-resolution patterning of high Tc superconductors

A 20 keV Ga focused ion beam has been used to pattern superconducting submicrometer bridge structures in thin films of Ba2YCu3O7 material by physical sputtering. The technique can produce structures down to 0.5 micron or less in epitaxial films with no degradation in superconducting transition temperature J or critical current density J. Photolithography was used to define a coarse pattern of 20-micron-wide and 50-micron-long strips, each wired for four-terminal resistance measurements. Submicrometer constrictions were then milled by the focused ion beam to form weak-link junctions with roughly 0.3 micron separating the superconducting banks. It has been demonstrated that focused ion beam micromachining is capable of producing submicrometer-sized superconducting structures. (Author)