Single-charge devices with ultrasmall Nb/AlOx/Nb trilayer Josephson junctions

摘要: Josephson junction transistors and 50-junction arrays with linear dimensions from 200 nm down to 70 were fabricated standard Nb/AlOx/Nb trilayers. The fabrication process includes electron beam lithography, dry etching, anodization, planarization by chemical-mechanical polishing. samples characterized at temperatures 25 mK. In general, all junctions are of high quality their I-U characteristics show low leakage currents superconducting energy gap values 1.35 meV. the exhibit some features in subgap area, associated tunneling Cooper pairs, quasiparticles combinations due redistribution bias voltage between junctions. Total island capacitances transistor ranged 1.5 fF 4 fF, depending on sizes. Devices made below 100 demonstrate a remarkable single-electron behavior both normal state. We also investigated area dependence for array samples.