Weak link properties of YBa2Cu3O7 nanostructures

YBa2Cu3O7 bridges with widths ranging from 50nm to 3 micrometers were made using electron beam lithography and focused ion beam milling. The current voltage characteristics of the nanobridges show, under microwave irradiation, pronounced Shapiro steps up to the transition temperature. SQUIDs, using these nanobridges, have been made and flux to voltage modulation up to 85K was observed, with a maximum modulation depth of 8 (mu) V at 77K. An unusual temperature dependence of the modulation is observed, which can be explained by assuming an exponential spatial distribution of the superconducting properties near the edge of a superconductor