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| Author |
Larrey, V.; Villegier, J. -C.; Salez, M.; Miletto-Granozio, F.; Karpov, A. |
| Title |
Processing and characterization of high Jc NbN superconducting tunnel junctions for THz analog circuits and RSFQ |
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Journal Article |
| Year |
1999 |
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IEEE Trans. Appl. Supercond. |
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9 |
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2 |
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3216-3219 |
| Keywords |
RSFQ, NbN, SIS |
| Abstract |
A generic NbN Superconducting Tunnel Junctions (STJ) technology has been developed using conventional substrates (Si and SOI-SIMOX) for making THz spectrometers including SIS receivers and RSFQ logic gates. NbN/MgO/NbN junctions with area of 1 /spl mu/m/sup 2/, Jc of 10 kA/cm/sup 2/ and low sub-gap leakage current (Vm>25 mV) are currently obtained from room temperature sputtered multilayers followed by a post-annealing at 250/spl deg/C. Using a thin MgO buffer layer deposited underneath the NbN electrodes, ensures lower NbN surface resistance values (Rs=7 /spl mu//spl Omega/) at 10 GHz and 4 K. Epitaxial NbN [100] films on MgO [100] with high gap frequency (1.4 THz) have also been achieved under the same deposition conditions at room temperature. The NbN SIS has shown good I-V photon induced steps when LO pumped at 300 GHz. We have developed an 8 levels Al/NbN multilayer process for making 1.5 THz SIS mixers (including Al antennas) on Si membranes patterned in SOI-SIMOX. Using the planarization techniques developed at the Si-MOS CEA-LETI Facility, we have also demonstrated on the possibility of extending our NbN technology to high level RSFQ circuit integration with 0.5 /spl mu/m/sup 2/ junction area, made on large area substrates (up to 8 inches). |
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1081 |
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Gurovich, B. A.; Tarkhov, M. A.; Prikhod'ko, K. E.; Kuleshova, E. A.; Komarov, D. A.; Stolyarov, V. L.; Olshanskii, E. D.; Goncharov, B. V.; Goncharova, D. A.; Kutuzov, L. V.; Domantovskii, A. G. |
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Controlled modification of superconducting properties of NbN ultrathin films under composite ion beam irradiation |
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Journal Article |
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2014 |
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Nanotechnologies in Russia |
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Nanotechnologies in Russia |
| Volume |
9 |
Issue |
7 |
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386-390 |
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superconducting NbN films composite ion beam irradiation protoning |
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In this work, the results of studying the microstructure and superconducting properties of ultrathin films on the basis of NbN in the initial state and after modification by being subjecting to composite ion beam irradiation with the energy ~1–3) keV are presented. HRTEM analysis showed that the initial films on the sapphire substrate in orientation “c-cut†are characterized by a grain size essentially exceeding the film thickness, while on the other substrates the size of grains corresponds to the thickness of film. Using XPS analysis, it was shown that in the initial films the atomic ratio of Nb and N is 0.51/0.49, respectively, the percentage of oxygen being lower than 5%. For ultrathin films 5 nm in thickness, the critical temperature of transit to superconducting state (T c) is found to be ~3.6 K and the density of critical current is jc ~8MA/cm2. In the work it is experimentally determined that the irradiation of NbN films by composite ion beams leads to the controlled modification of its superconducting properties due to the process of selective substitution of nitrogen atoms on the oxygen atoms. |
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1000 |
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Maslennikov, S. |
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RF heating efficiency of the terahertz superconducting hot-electron bolometer |
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Journal Article |
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2014 |
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arXiv |
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arXiv |
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1404.5276 |
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1-4 |
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superconducting hot-electron bolometer mixer, HEB, NbN, distributed model, HEB model, HEB mixer model, heat balance equa-tions, conversion gain, RF heating efficiency, noise temperature, simulation, Euler method |
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We report results of the numerical solution by the Euler method of the system of heat balance equations written in recurrent form for the superconducting hot-electron bolometer (HEB) embedded in an electrical circuit. By taking into account the dependence of the HEB resistance on the transport current we have been able to calculate rigorously the RF heating efficiency, absorbed local oscillator (LO) power and conversion gain of the HEB mixer. We show that the calculated conversion gai nis in excellent agreement with the experimental results, and that the substitution of the calculated RF heating efficiency and absorbed LO power into the expressions for the conversion gain and noise temperature given by the analytical small-signal model of the HEB yields excellent agreement with the corresponding measured values |
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RPLAB @ atomics90 @ |
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954 |
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Kawamura, J.; Blundell, R.; Tong, C.-Y. E.; Golts'man, G.; Gershenzon, E.; Voronov B. |
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Superconductive NbN hot-electron bolometric mixer performance at 250 GHz |
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Conference Article |
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1996 |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
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Proc. 7th Int. Symp. Space Terahertz Technol. |
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331-336 |
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NbN HEB mixers |
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Thin film NbN (<40 A) strips are used as waveguide mixer elements. The electron cooling mechanism for the geometry is the electron-phonon interaction. We report a receiver noise temperature of 750 K at 244 GHz, with / IF = 1.5 GHz, Af= 500 MHz, and Tphysical = 4 K. The instantaneous bandwidth for this mixer is 1.6 GHz. The local oscillator (LO) power is 0.5 1.tW with 3 dB-uncertainty. The mixer is linear to 1 dB up to an input power level 6 dB below the LO power. We report the first detection of a molecular line emission using this class of mixer, and that the receiver noise temperature determined from Y-factor measurements reflects the true heterodyne sensitivity. |
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945 |
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Miao, W.; Zhang, W.; Zhong, J. Q.; Shi, S. C.; Delorme, Y.; Lefevre, R.; Feret, A; Vacelet, T |
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Non-uniform absorption of terahertz radiation on superconducting hot electron bolometer microbridges |
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Journal Article |
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2014 |
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Appl. Phys. Lett. |
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<ef><bf><bc>Appl. Phys. Lett. |
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104 |
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052605(1-4) |
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NbN HEB mixers, local oscillator power, RF nonuniform absorption |
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We interpret the experimental observation of a frequency-dependence of superconducting hot electron bolometer (HEB) mixers by taking into account the non-uniform absorption of the terahertz radiation on the superconducting HEB microbridge. The radiation absorption is assumed to be proportional to the local surface resistance of the HEB microbridge, which is computed using the Mattis-Bardeen theory. With this assumption the dc and mixing characteristics of a superconducting niobium-nitride (NbN) HEB device have been modeled at frequencies below and above the equilibrium gap frequency of the NbN film. |
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935 |
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