Properties of superconducting weak links produced by ion implantation

A new technique has been developed for making superconducting weak links, making use of the fact that the superconducting transition temperature (T/subc/) of certain metals (e.g., W, Mo) can be greatly increased by ion implantation. By implanting controlled patterns of N+ and S+ ions into Mo films, structures have been produced in which two heavily doped Mo regions with high T/subc/ are joined by a short (approximately-less-than1 μm) lightly doped Mo region with lower T/subc/ which acts as a weak link. These rugged and stable structures display the ac and dc Josephson effects. These techniques lend themselves to the production of superconducting integrated circuits containing weak links