Resolution limits of ion milling for fabricating Y1Ba2Cu3Ox nanostructures

A process is described for fabricating 0.23-μm-wide lines in Y1Ba2Cu3Ox thin films where patterns are defined in a commercial, negative tone, epoxy-based resist by masked ion beam lithography and transferred to the superconducting film by argon ion milling. Lines in 80-nm-thick films had the same zero-resistance temperature (89 K) as the starting films, and a critical current density of 0.7×106 A/cm2 at 77 K, representing a threefold reduction from the starting value. A consistent interpretation of these results is that the line consists of a superconducting core 70 nm in width with the critical current density of the starting film and with 80-nm-wide nonsuperconducting sidewalls. The results were reproducible in lines which did not cross outgrowths in the superconducting film.