Stability and uniformity of planar high temperature Josephson junctions fabricated using nanolithography and ion damage

We have investigated the room temperature stability and the critical curren t uniformity of planar thin film YBa2Cu3O7-delta Josephson junctions. The j unctions were fabricated using electron-beam lithography to define a stenci l structure followed by ion damage from a conventional 200 keV ion implante r. Using this technique, we have fabricated junctions with weak link length s of 20 - 100 nm that showed classical de and ac Josephson effects at 77 K. By a suitable choice of damage and stencil width, these devices may be tun ed to operate at any temperature between 1 K and the bulk transition temper ature, and they may be placed anywhere on a wafer, providing a high degree of flexibility for circuit applications. Results obtained over several mont hs showed a high level of room temperature stability, and the uniformity of the junctions was maintained.