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Author Khosropanah, P.; Gao, J. R.; Laauwen, W. M.; Hajenius, M; Klapwijk, T. M.
Title Low noise NbN hot electron bolometer mixer at 4.3 THz Type Journal Article
Year (up) 2007 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.
Volume 91 Issue Pages 221111 (1 to 3)
Keywords NbN HEB mixers, NbN, contacts cleaning
Abstract We have studied the sensitivity of a superconducting NbN hot electron bolometer mixer integrated with a spiral antenna at 4.3 THz. Using hot/cold blackbody loads and a beam splitter all in vacuum, we measured a double sideband receiver noise temperature of 1300 K at the optimum local oscillator (LO) power of 330 nW, which is about 12 times the quantum noise (hnu/2kB). Our result indicates that there is no sign of degradation of the mixing process at the superterahertz frequencies. Moreover, a measurement method is introduced which allows us for an accurate determination of the sensitivity despite LO power fluctuations.
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Call Number Serial 584
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Author Kooi, J. W.; Baselmans, J. J. A.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M.; Dieleman, P.; Baryshev, A.; de Lange, G.
Title IF impedance and mixer gain of NbN hot electron bolometers Type Journal Article
Year (up) 2007 Publication J. Appl. Phys. Abbreviated Journal
Volume 101 Issue 4 Pages 044511
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ISSN 0021-8979 ISBN Medium
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Notes Approved no
Call Number RPLAB @ s @ Serial 445
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Author Gao, J. R.; Hajenius, M.; Yang, Z. Q.; Baselmans, J. J. A.; Khosropanah, P.; Barends, R.; Klapwijk, T. M.
Title Terahertz superconducting hot electron bolometer heterodyne receivers Type Journal Article
Year (up) 2007 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal
Volume 17 Issue 2 Pages 252-258
Keywords HEB, mixer, direct detection effect
Abstract We highlight the progress on NbN hot electron bolometer (HEB) mixers achieved through fruitful collaboration between SRON Netherlands Institute for Space Research and Delft University of Technology, the Netherlands. This includes the best receiver noise temperatures of 700 K at 1.63 THz using a twin-slot antenna mixer and 1050 K at 2.84 THz using a spiral antenna coupled HEB mixer. The mixers are based on thin NbN films on Si and fabricated with a new contact-process and-structure. By reducing their areas HEB mixers have shown an LO power requirement as low as 30 nW. Those small HEB mixers have demonstrated equivalent sensitivity as those with large areas provided the direct detection effect due to broadband radiation is removed. To manifest that a HEB based heterodyne receiver can in practice be used at arbitrary frequencies above 2 THz, we demonstrate a 2.8 THz receiver using a THz quantum cascade laser (QCL) as local oscillator.
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ISSN 1051-8223 ISBN Medium
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Notes Approved no
Call Number RPLAB @ asmirn @ Serial 557
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Author Hajenius, M.; Yang, Z. Q.; Gao, J. R.; Baselmans, J. J. A.; Klapwijk, T. M.; Voronov, B.; Gol'tsman, G.
Title Optimized sensitivity of NbN hot electron bolometer mixers by annealing Type Journal Article
Year (up) 2007 Publication IEEE Trans. Appl. Supercond. Abbreviated Journal IEEE Trans. Appl. Supercond.
Volume 17 Issue 2 Pages 399-402
Keywords NbN HEB mixers
Abstract We report that the heterodyne sensitivity of superconducting hot-electron bolometers (HEBs) increases by 25-30% after annealing at 85degC in high vacuum. The devices studied are twin-slot antenna coupled mixers with a small area NbN bridge of 1 mum times 0.15 mum, above which there is a SiO 2 passivation layer. The mixer noise temperature, gain, and resistance versus temperature curve of a HEB before and after annealing are compared and analysed. We show that the annealing reduces the intrinsic noise of the mixer by 37% and makes the superconducting transition of the bridge and the contacts sharper. We argue that the reduction ofthe noise is mainly due to the improvement of the transparency of the contact/film interface. The lowest receiver noise temperature of 700 K is measured at a local oscillator frequency of 1.63 THz and at a bath temperature of 4.2 K.
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ISSN 1051-8223 ISBN Medium
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Notes Approved no
Call Number Serial 1426
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Author Gao, J. R.; Hajenius, M.; Tichelaar, F. D.; Klapwijk, T. M.; Voronov, B.; Grishin, E.; Gol’tsman, G.; Zorman, C. A.; Mehregany, M.
Title Monocrystalline NbN nanofilms on a 3C-SiC∕Si substrate Type Journal Article
Year (up) 2007 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.
Volume 91 Issue 6 Pages 062504 (1 to 3)
Keywords NbN films, nanofilms
Abstract The authors have realized NbN (100) nanofilms on a 3C-SiC (100)/Si(100) substrate by dc reactive magnetron sputtering at 800°C. High-resolution transmission electron microscopy (HRTEM) is used to characterize the films, showing a monocrystalline structure and confirming epitaxial growth on the 3C-SiC layer. A film ranging in thickness from 3.4to4.1nm shows a superconducting transition temperature of 11.8K, which is the highest reported for NbN films of comparable thickness. The NbN nano-films on 3C-SiC offer a promising alternative to improve terahertz detectors. For comparison, NbN nanofilms grown directly on Si substrates are also studied by HRTEM.

The authors acknowledge S. V. Svetchnikov at National Centre for HRTEM at Delft, who prepared the specimens for HRTEM inspections. This work was supported by the EU through RadioNet and INTAS.
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Series Volume Series Issue Edition
ISSN 0003-6951 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1425
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