High frequency behavior of long and small junctions

Results are presented of studies on long Josephson junctions and on very small junctions. The long junctions are made out of NbN. Experiments were made on the lifetimes of fluxon states from 2 to 0.01 K; they are of importance to a fundamental understanding of tunneling and nucleation. Multifluxon resonances were observed and they are of interest to the application of long junctions as high frequency oscillators. Very small junctions, all NbN, were fabricated using a STM approach. Results show the Coulomb blockade, the Coulomb staircase, and the staircase, and the superconducting energy gap. The two types of junctions are being combined to observe Bloch oscillations.