Presently, niobium nitrogen (nbn)-based josephson junctions are probably the best candidates for superconducting logic circuity. Unfortunately, current technology cannot produce barrier films of uniform thickness, consistent from batch to batch. Uniform mgo barrier layers are needed to prevent oxides from forming, which react with nbn counterelectrodes-causinga short circuit. This project will make nbn insulators and josephson junctions with very high yields. The project will prepare barrier layers on superconducting nbn films, which allows nbn counterelectrodesto be deposited without damaging the barrier layer. This thin-film fabrication method also improves reproducibility. In addition, the method increases control of the critical current. The method produces circuits that are rugged, i.e. They can be thermally cycled. Further, the circuits can be used with mechanical closed-cycle refrigerators, and do not require cooling by liquid helium. Applications for the circuits include reflectomemters, wave mixers, and digital logic gates. Nbn logic circuits of 10 (5th power) junctions or higher could be built, which would make possible faster microprocessors.
