Fabrication of nis and sis nanojunctions with aluminum electrodes and studies of magnetic field influence on iv curves

Samples of superconductor–insulator–superconductor (SIS) and normal metal–insulator– superconductor (NIS) junctions with superconducting aluminum of different thickness were fabricated and experimentally studied, starting from conventional shadow evaporation with a suspended resist bridge. We also developed alternative fabrication by magnetron sputtering with twostep direct e-beam patterning. We compared Al film grain size, surface roughness, resistivity deposited by thermal evaporation and magnetron sputtering. The best-quality NIS junctions with large superconducting electrodes approached a resistance R(0)/R(V2Δ) factor ratio of 1000 at 0.3 K and over 10,000 at 0.1 K. At 0.1 K, R(0) was determined completely by the Andreev current. The contribution of the single-electron current dominated at V > VΔ/2. The single-electron resistance extrapolated to V = 0 exceeded the resistance R(V2Δ) by 3 7 109. We measured the influence of the magnetic field on NIS junctions and described the mechanism of additional conductivity due to induced Abrikosov vortices. The modified shape of the SINIS bolometer IV curve was explained by Joule overheating via NIN (normal metal–insulator–normal metal) channels

Realization of Cold-Electron Bolometers with Ultimate Sensitivity due to Strong Electron Self-Cooling

We have realized an ultimate photon-noise-limited array of cold-electron bolometers (CEBs) for OLIMPO Balloon Telescope. The CEB array demonstrates very effective electron self-cooling of the absorber from 310 mK to 100 mK without optical power load, P-0, and from 310 mK to 160 mK with P-0=20 pW at v=345 GHz. Due to this effective electron cooling acting as strong electrothermal feedback, the ultimate photon-noise-limited mode of operation is realized in the range of P-0 starting from 8 pW and up to P-0=20 pW at T-ph=330 mK. To our knowledge, there is no analog in the world for bolometers working at electron temperature less than phonon temperature