Submicron ion beam modification of high-Tc superconducting bridges

We have investigated the modification of high-Tc superconducting film structures due to ion beam irradiation using a mask technology. The YBa2Cu3O7 (YBCO) and GdBa2Cu3O7 (GBCO) thin film microbridges were covered with electron resist (PMMA) masks. Then, a submicron slit was patterned by e-beam lithography. The high-Tc bridges were modified by irradiation with argon ions. Fluence and energy of the ions could be varied and the change in the electrical properties of the modified regions have been measured. For suitable values of ion energy and fluence we measured Shapiro steps in the current-voltage curves under microwave irradiation for a temperature range of a few Kelvin just below the critical temperature. We found a modulation of the Shapiro steps with increasing microwave power and compared the power dependence to Josephson and flux flow behaviour. The Monte-Carlo program TRIM was used for characterization of the ion solid interaction, especially for the estimation of range, damage distribution and straggling in dependence on geometry. (orig.)