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Author Baselmans, J. J. A.; de Visser, P. J.; Yates, S. J. C.; Bueno, J.; Jansen, R. M. J.; Endo, A.; Thoen, D. J.; Baryshev, A. M.; Ferrari, L.; Klapwijk, T. M.
Title Large format, background limited arrays of kinetic inductance detectors for sub-mm astronomy Type Abstract
Year 2014 Publication Proc. 25th Int. Symp. Space Terahertz Technol. Abbreviated Journal Proc. 25th Int. Symp. Space Terahertz Technol.
Volume Issue Pages 64
Keywords (up) KID
Abstract Kinetic Inductance detectors have held a promise for the last decade to enable very large arrays, in excess of 10.000 pixels, with background limited sensitivity for ground- and Space Based sub-mm observatories. First we present the development of the detector chips of the A-MKID instrument: These chips contain up to 5400 detector pixel divided over up to 5 readout lines for the 350 GHz and 850 GHz atmospheric windows. The individual detectors are lens antenna coupled KIDs made of NbTiN and Aluminium that reach photon noise limited sensitivity at sky loading levels in excess of a few fW per pixel using either phase readout or amplitude readout. The ability to use phase readout is crucial as it reduces the requirements on the readout electronics of the instrument. Cross coupling between the KID resonators was mitigated by a combination of numerical simulations and a suitable position encoding of the readout resonance frequencies of the individual pixels. Beam pattern measurements are performed to demonstrate the absence of any cross talk due to resonator- resonator cross coupling. Second we present experiments on individual lens-antenna coupled detectors at 1.5 THz that are made out of aluminium. With these devices we have observed, as a function of the irradiated power at 1.5 THz, the crossover from photon noise limited performance to detector-limited performance at loading powers less than 0.1 fW. In the latter limit the device is limited by intrinsic fluctuations in the Cooper pair and quasiparticle number, i.e. Generation-Recombination noise. This results in a sensitivity corresponding to a NEP = 3.8·10 -19 W/√(Hz).
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Call Number Serial 1360
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Author Bueno, J.; Coumou, P. C. J. J.; Zheng, G.; de Visser, P. J.; Klapwijk, T. M.; Driessen, E. F. C.; Doyle, S.; Baselmans, J. J. A
Title Anomalous response of superconducting titanium nitride resonators to terahertz radiation Type Journal Article
Year 2014 Publication Appl. Phys. Lett. Abbreviated Journal
Volume 105 Issue Pages 192601 (1 to 5)
Keywords (up) KID, TiN, NEP, disordered superconductors, inhomogeneous state
Abstract We present an experimental study of kinetic inductance detectors (KIDs) fabricated of atomic layer deposited TiN films and characterized at radiation frequencies of 350 GHz. The responsivity to radiation is measured and found to increase with the increase in radiation powers, opposite to what is expected from theory and observed for hybrid niobium titanium nitride/aluminium (NbTiN/Al) and all-aluminium (all-Al) KIDs. The noise is found to be independent of the level of the radiation power. The noise equivalent power improves with higher radiation powers, also opposite to what is observed and well understood for hybrid NbTiN/Al and all-Al KIDs. We suggest that an inhomogeneous state of these disordered superconductors should be used to explain these observations.
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Notes Approved no
Call Number Serial 1068
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Author Finkel, M.; Thierschmann, H. R.; Galatro, L.; Katan, A. J.; Thoen, D. J.; de Visser, P. J.; Spirito, M.; Klapwijk, T. M.
Title Branchline and directional THz coupler based on PECVD SiNx-technology Type Conference Article
Year 2016 Publication 41st IRMMW-THz Abbreviated Journal 41st IRMMW-THz
Volume Issue Pages
Keywords (up) microstrip, fixtures, coplanar waveguides, couplers, standards, probes, dielectrics
Abstract A fabrication technology to realize THz microstrip lines and passive circuit components is developed and tested making use of a plasma-enhanced chemical vapor deposition grown silicon nitride (PECVD SiNx) dielectric membrane. We use 2 μm thick SiNx and 300 nm thick gold layers on sapphire substrates. We fabricate a set of structures for thru-reflect-line (TRL) calibration, with the reflection standard implemented as a short through the via. We find losses of 9.5 dB/mm at 300 GHz for a 50 Ohm line. For a branchline coupler we measure 2.5 dB insertion loss, 1 dB amplitude imbalance and 21 dB isolation. Good control over the THz lines parameters is proven by similar performance of a set of 5 structures. The directional couplers show -14 dB transmission to the coupled port, -24 dB to the isolated port and -25 dB in reflection. The SiNx membrane, used as a dielectric, is compatible with atomic force microscopy (AFM) cantilevers allowing the application of this technology to the development of a THz near-field microscope.
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ISSN 2162-2035 ISBN 978-1-4673-8485-8 Medium
Area Expedition Conference
Notes Approved no
Call Number 7758586 Serial 1295
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Author Heslinga, D. R.; Shafranjuk, S. E.; van Kempen, H.; Klapwijk, T. M.
Title Observation of double-gap-edge Andreev reflection at Si/Nb interfaces by point-contact spectroscopy Type Journal Article
Year 1994 Publication Phys. Rev. B Abbreviated Journal Phys. Rev. B
Volume 49 Issue 15 Pages 10484-10494
Keywords (up) Nb, Si, Nb-Si, Nb/Si, Si/Nb, Andreev reflection, point-contact spectroscopy
Abstract Andreev reflection point-contact spectroscopy is performed on a bilayer consisting of 50-nm degenerately doped Si backed with Nb. Due to the short mean free path both injection into and transport across the Si layer are diffusive, in contrast to the ballistic conditions prevailing in clean metal layers. Nevertheless a large Andreev signal is observed in the point-contact characteristics, not reduced by elastic scattering in the Si layer or by interface scattering, but only limited by the transmission coefficient of the metal-semiconductor point contact. Two peaks in the Andreev reflection probability are visible, marking the values of the superconducting energy gap at the interface on the Nb and Si sides. This interpretation is supported by a method of solving the Bogolubov equations analytically using a simplified expression for the variation of the order parameter close to the interface. This observation enables a comparison with theoretical predictions of the gap discontinuity in the proximity effect. It is found that the widely used de Gennes model does not agree with the experimental data.
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Publisher American Physical Society Place of Publication Editor
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Notes Approved no
Call Number Serial 1005
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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 2007 Publication Appl. Phys. Lett. Abbreviated Journal Appl. Phys. Lett.
Volume 91 Issue 6 Pages 062504 (1 to 3)
Keywords (up) 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 Editor Series Title Abbreviated Series Title
Series Volume Series Issue Edition
ISSN 0003-6951 ISBN Medium
Area Expedition Conference
Notes Approved no
Call Number Serial 1425
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