Orientation control of YBa2Cu3O7 thin films on MgO for epitaxial junctions

A low-temperature argon ion milling process has been used to induce growth of c-oriented YBa₂Cu₃O₇ on (001) MgO substrates with the in-plane film axes rotated 45° with respect to those of the substrate, and with respect to those of films grown on untreated regions of the substrate. This process is compatible with standard photolithographic processing, and has been used to produce defined areas of the two orientations on the same substrate. Josephson junctions and dc SQUIDs have been fabricated using the resulting grain boundaries.