Berlin 2008 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
TT: Fachverband Tiefe Temperaturen
TT 15: Superconductivity: Poster Session
TT 15.49: Poster
Dienstag, 26. Februar 2008, 14:00–18:00, Poster B
Proximity Effect in Nb/Au and NbN/Au bi-layers for THz Antenna Structures of HEB Mixers — •Axel Stockhausen1, Konstantin Il’in1, Michael Siegel1, Alexei Semenov2, Heinz- Wilhelm Hübers2, Reinhard Schneider3, and Dagmar Gerthsen3 — 1IMS, University of Karlsruhe, Karlsruhe, Germany — 2DLR e.V. Institute of Planetary Research, Berlin, Germany — 3LEM, University of Karlsruhe, Karlsruhe, Germany
Hot-electron Bolometer (HEB) mixers are high sensitive heterodyne detectors made from ultra-thin (<5 nm) NbN film deposited on Si substrate. For proper operation of these devices in THz frequency range a superconducting detecting element is embedded into antenna structure made from thick Au layer. In systems where a superconducting film with thickness about the coherence length is in contact with a thick normal metal layer superconductivity will be suppressed due to proximity effect. Increasing transparency of superconducting-to-normal metal interface leads to stronger suppression of superconductivity in ultra-thin NbN film. However it allows to decrease RF losses on contact resistance between antenna and detecting element and improve performance of HEB mixer. We have developed processes for deposition of Au antenna structure with superconducting buffer of Nb or NbN. This allows us to avoid deterioration of HEB mixer performance causing by proximity effect even in case of perfectly transparent interface. The superconducting and normal state properties of different Nb and NbN thin films and Nb/Au and NbN/Au bi- and multi-layers will be presented and properties of the interfaces will be discussed.