Fabrication of Ultra-Small Nb-AlOx-Nb Josephson Tunnel Junctions | NIST

Paola Barbara, G. Costabile

Lucia Capogna, Giovanni Costabile, Paola Barbara +2 more

Jun Kawai, Gen Uehara, Naoki Mizutani +3 more

John M. Martinis, Ronald H. Ono

We describe a fabrication process to make Nb-AlOx-Nb edge junctions with areas as small as 0.0022 μm2 and with current densities from 10 to 24 000 A/cm2. The junction conductance was low for voltages below the superconducting energy gap which indicates good quality tunnel barriers. Coulomb gap measurements obtained when the junctions were in the normal state were used to find the junction capacitance. Junction capacitance as small as 0.18 fF has been measured.

Faouzi M. Boussaha, A. Féret, Christine Chaumont +9 more

We report on the first direct detection of submillimeter waves emitted by small parallel tunnel junction arrays. The arrays made up of 10 and 20 Nb/Al-AlOx/Nb junctions of 6 μm2is integrated and coupled in RF to Nb/Al-AlOx/Nb twin junction-based detector by a microstrip/slotline transition. The detector's I-V curve exhibits clearly photonassisted steps when the array is biased on the corresponding Josephson resonance at 390 and 480 GHz. These results are of particular significance in the light of previous work done on this type of devices. The arrays are specially suited for applications such as clock for RSFQ electronics or as local oscillator for THz superconducting integrated receivers.

林冠宇, Kuan-Yu Lin