High Frequency Behavior of Long and Small Junctions

Abstract

Abstract : This research consisted of studies of the fundamentals and applications of long Josephson Junctions and very small junctions, all fabricated out of NbN. We have developed technology for fabricating by reactive sputtering high quality long Josephson junctions with current densities of 100- 1,000 A/sq cm Such junctions were used for studies of giant steps on the I-V curve caused by fluxon pinning and of macroscopic quantum tunneling down to 15 mK. A new system, a long Josephson junction biased at Fiske steps, is presented for studies of Macroscopic Quantum Tunneling. Our results show applications of fluxons in long Josephson junctions for Fluxon Oscillator, Voltage Standard, and for observing Macroscopic Coherent Tunneling. We, have also studied very small NbN junctions fabricated with a STM where single electron tunneling is observed. We were the first to present such tunneling at room temperature; this is important for applications. Students and postdoctoral fellows were involved in this research.