Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of Physics Conference Series

Study of SNS and SIS NbN Josephson junctions coupled to a microwave band-pass filter

Emanuele Baggetta, Romano Setzu, J.C. Villégier

Published Jun 1, 2006• 3 citations
Publisher

Abstract

We have fabricated both NbN/Ta x N/NbN SN*S-type, NbN/MgO/NbN SIS-type Josephson junctions and microwave band-pass filters on different substrates (Si, Sapphire, MgO). NbN films have been deposited on both sides of (100) oriented, 250 µm thick, MgO substrates with a high crystalline texture quality. The aim was to investigate the performances and the maximum achievable operating frequency in an NbN based RSFQ modulator front-end of an ADC in the 4 K-10 K temperature range. We observed that Ta x N thin films can be tuned from an insulating phase to a superconducting phase (Tc ∼4K) by varying the nitrogen content during sputter deposition while the barrier height of MgO can also be controlled by deposition conditions and by tri-layer postdeposition annealing. Junction properties (Jc∼10-25 kA/cm 2 ), Mac Cumber parameter and RnIc product measured up to 1 mV are shown to be controlled by the reactive sputtering conditions. We have designed three pole band-pass filters and resonators in a micro-strip configuration and studied the junction coupling with the filters. We will show that a sigma-delta NbN technology is a suitable solution for analogue-to-digital conversion in the future generations of telecommunication satellites to achieve high sampling frequency and large bandwidth at high carrier frequency signal.

DOI
10.1088/1742-6596/43/1/284

Related papers

New Design and Implementation of a Fast Modulator in NbN Technology

Emanuele Baggetta, Bjoern Ebert, N. Hadacek +2 more

We have designed a band-pass sigma-delta modulator made in niobium nitride technology. The basic components of such a 10 GHz carrier frequency modulator are a band filtering resonator and an SFQ comparator synchronized with a clock frequency up to 200 GHz sampling rate. We describe the clock design including an internal JTL and its testing circuit based on frequency division. The technology involves NbN/Ta/sub x/N/NbN internally shunted Josephson junctions with Jc/spl sim/20kA/cm/sup 2/ and high RnIc product (/spl sim/1 mV) at 4.2 K. Junction parameters are shown to be controlled by the reactive sputtering conditions of the Ta/sub x/N barrier. SiO/sub 2//MgO bi-layers are used as dielectrics associated with NbN wiring layers and ground-plane. All layers are prepared in a way compatible with a full processing at about 350/spl deg/C in order to minimize the London penetration depth of NbN layers and thus to allow circuits operation at about 9 K. High frequency simulations of the modulator's circuits are presented, including the comparator, the DEMUX, and the resonator response.

IEEE Transactions on Applied Superconductivity•Jun 1, 2005•8 citations

Processing and characterization of high Jc NbN superconducting tunnel junctions for THz analog circuits and RSFQ

Vincent Larrey, J.C. Villégier, Morvan C. Salez +2 more

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).

IEEE Transactions on Applied Superconductivity•Jun 1, 1999•14 citations

NbN/AlN/NbN Josephson Junctions on Sapphire for SIS Receiver Applications

Michael Merker, Christian Bohn, Marvin Vollinger +2 more

The most developed integrated receivers for THz radiation nowadays are based on Josephson junction superconductor-insulator-superconductor devices. In this kind of devices, the highest receivable frequency is determined by the energy gap of the superconducting electrodes and limited to approximately 700 GHz in case of Nb/AlOx/Nb multilayers. We have developed a technology for NbN/AlN/NbN Josephson junctions on sapphire substrates which allow operation at frequencies above 1 THz. The trilayers are deposited in situ in a three-chamber dc-magnetron sputtering system at temperatures as high as 775 °C. Each layer is reactively sputtered in an argon and nitrogen atmosphere. By variation of the partial gas pressures and discharge current of the plasma, optimum deposition conditions for the tri-layers were found. So far, gap voltages as high as 5.1 mV at 4.2 K have been achieved which allows the operation frequency of the JJ devices to exceed 1 THz.

arXiv:1612.02713•IEEE Transactions on Applied Superconductivity•Dec 9, 2016•6 citations

Integration of Planarized Internally-Shunted Submicron NbN Junctions

Jean-Claude Villégier, Sophie Bouat, Mario Aurino +2 more

NbN-TaN-Nb(Ti)N non-hysteretic SNS Josephson junctions with TaXN barriers tuned through nitrogen content at metal-insulator transition have been produced in a reliable way with characteristic voltage RNICabove 1.5 mV at 9 K. Barriers are typically 7-10 nm thick and Jc in the range 5 to 25 kA/cm-2making feasible LSI RSFQ ADC circuit integration by using the lithographic tools of the Leti C-MOS platform. Junction tri-layers, NbTiN ground-plane and wiring levels have been reactively sputtered and optimized at 300°C in a reproducible way on 8-inch oxidized silicon wafers. A deep UV stepper combined with SF6 gas mixtures RIE has been used to achieve low spread lithography in junction diameters of 716 nm (3σ ~ 40 nm), of 465 nm (3σ ~ 84 nm) across the 8-inch. A well controlled CMP planarization process has been developed on thick PE-CVD silica layers deposited on each superconducting nitride layer. On-line FIB-SEM observations and electrical characterizations associated to the development of a technology test vehicle demonstrate the feasibility of the complete process. The reliable production of nitrides LSI RSFQ circuits such as ADCs and integrated imagers operating in a relaxed cryogenic environment in the 6-10 K temperature range is foreseen to open new telecoms and medical applications. Moreover, a new MgO-AlN-MgO layered insulating barrier junction is shown to operate above 10 K and will be developed for analog front-end circuit parts.

IEEE Transactions on Applied Superconductivity•Dec 9, 2010•13 citations

NBN JOSEPHSON AND TUNNEL JUNCTIONS FOR SPACE THZ OBSERVATION AND SIGNAL PROCESSING

Romano Setzu, N. Hadacek, Vincent Larrey +2 more

ABSTRACT: Active superconducting circuits based on picoseconds switching, i.e. THz oscillating, Josephson tunnel junctions are expected to find a large domain of applications in spatial sub-millimeter wave and FIR detectors as well as in satellite based wideband signal and data processors. In the first case SIS (superconductor-insulator-superconductor) tunnel junctions are required, while in the second case SNS (superconductor-normal metal-superconductor) self-shunted junctions are preferred. We present the advantages of the nitride junction technology currently developed at CEA-Grenoble, based on high-performance MTS (medium temperature superconductor) NbN films in both SIS and SNS junctions. In the SIS case the device performances rely on a sputter deposited and post-annealed, only 0.5-0.7 nm thick, dielectric MgO barrier. This leads to junctions with a Josephson critical current in the range of 10-25 kA/cm, and a large superconducting energy gap (> 5 meV) associated with a low sub-gap quasi-particle leakage current. These parameters are suitable for low “noise temperature ” heterodyne mixers, local oscillators, and integrated receivers in the 0.8 to 1.4 THz frequency range. In the SNS case, a new

•Jul 13, 2005•1 citation

Low-loss epitaxial NbN/MgO/NbN trilayers for THz applications

Akira Kawakami, Zhen Wang, Shigehito Miki

To improve the performance of Josephson oscillators and SIS mixers over 700 GHz, we have developed a fabrication process to grow epitaxial NbN/MgO/NbN trilayers by reactive dc-sputtering. Trilayers were fabricated on a single-crystal MgO substrate at ambient temperature. NbN and MgO films were deposited by reactive dc-sputtering with an Nb and Mg target, respectively. The MgO inter-layer thickness was changed up to 480 nm, but, T/sub C/ and 20-K resistivity of the NbN upper-layer showed no remarkable dependency and they were 15.7 K and about 60 /spl mu//spl Omega/cm, respectively. To evaluate the RF performance of the epitaxial NbN films, we fabricated Josephson junctions with a microstrip resonator constructed from an epitaxial NbN/MgO/NbN trilayer. The I-V characteristics of the junction exhibited resonance steps up to 2.5 mV, which suggests that the epitaxial NbN films have low loss up to 1.2 THz.

IEEE Transactions on Applied Superconductivity•Mar 1, 2001•30 citations
We have fabricated both NbN/Ta x N/NbN SN*S-type, NbN/MgO/NbN SIS-type Josephson junctions and microwave band-pass filters on different substrates (Si, Sapphire, MgO). NbN films have been deposited on both sides of (100) oriented, 250 µm thick, MgO substrates with a high crystalline texture quality. The aim was to investigate the performances and the maximum achievable operating frequency in an NbN based RSFQ modulator front-end of an ADC in the 4 K-10 K temperature range. We observed that Ta x N thin films can be tuned from an insulating phase to a superconducting phase (Tc ∼4K) by varying the nitrogen content during sputter deposition while the barrier height of MgO can also be controlled by deposition conditions and by tri-layer postdeposition annealing. Junction properties (Jc∼10-25 kA/cm 2 ), Mac Cumber parameter and RnIc product measured up to 1 mV are shown to be controlled by the reactive sputtering conditions. We have designed three pole band-pass filters and resonators in a micro-strip configuration and studied the junction coupling with the filters. We will show that a sigma-delta NbN technology is a suitable solution for analogue-to-digital conversion in the future generations of telecommunication satellites to achieve high sampling frequency and large bandwidth at high carrier frequency signal.
We have designed a band-pass sigma-delta modulator made in niobium nitride technology. The basic components of such a 10 GHz carrier frequency modulator are a band filtering resonator and an SFQ comparator synchronized with a clock frequency up to 200 GHz sampling rate. We describe the clock design including an internal JTL and its testing circuit based on frequency division. The technology involves NbN/Ta/sub x/N/NbN internally shunted Josephson junctions with Jc/spl sim/20kA/cm/sup 2/ and high RnIc product (/spl sim/1 mV) at 4.2 K. Junction parameters are shown to be controlled by the reactive sputtering conditions of the Ta/sub x/N barrier. SiO/sub 2//MgO bi-layers are used as dielectrics associated with NbN wiring layers and ground-plane. All layers are prepared in a way compatible with a full processing at about 350/spl deg/C in order to minimize the London penetration depth of NbN layers and thus to allow circuits operation at about 9 K. High frequency simulations of the modulator's circuits are presented, including the comparator, the DEMUX, and the resonator response.
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).
The most developed integrated receivers for THz radiation nowadays are based on Josephson junction superconductor-insulator-superconductor devices. In this kind of devices, the highest receivable frequency is determined by the energy gap of the superconducting electrodes and limited to approximately 700 GHz in case of Nb/AlOx/Nb multilayers. We have developed a technology for NbN/AlN/NbN Josephson junctions on sapphire substrates which allow operation at frequencies above 1 THz. The trilayers are deposited in situ in a three-chamber dc-magnetron sputtering system at temperatures as high as 775 °C. Each layer is reactively sputtered in an argon and nitrogen atmosphere. By variation of the partial gas pressures and discharge current of the plasma, optimum deposition conditions for the tri-layers were found. So far, gap voltages as high as 5.1 mV at 4.2 K have been achieved which allows the operation frequency of the JJ devices to exceed 1 THz.
NbN-TaN-Nb(Ti)N non-hysteretic SNS Josephson junctions with TaXN barriers tuned through nitrogen content at metal-insulator transition have been produced in a reliable way with characteristic voltage RNICabove 1.5 mV at 9 K. Barriers are typically 7-10 nm thick and Jc in the range 5 to 25 kA/cm-2making feasible LSI RSFQ ADC circuit integration by using the lithographic tools of the Leti C-MOS platform. Junction tri-layers, NbTiN ground-plane and wiring levels have been reactively sputtered and optimized at 300°C in a reproducible way on 8-inch oxidized silicon wafers. A deep UV stepper combined with SF6 gas mixtures RIE has been used to achieve low spread lithography in junction diameters of 716 nm (3σ ~ 40 nm), of 465 nm (3σ ~ 84 nm) across the 8-inch. A well controlled CMP planarization process has been developed on thick PE-CVD silica layers deposited on each superconducting nitride layer. On-line FIB-SEM observations and electrical characterizations associated to the development of a technology test vehicle demonstrate the feasibility of the complete process. The reliable production of nitrides LSI RSFQ circuits such as ADCs and integrated imagers operating in a relaxed cryogenic environment in the 6-10 K temperature range is foreseen to open new telecoms and medical applications. Moreover, a new MgO-AlN-MgO layered insulating barrier junction is shown to operate above 10 K and will be developed for analog front-end circuit parts.
ABSTRACT: Active superconducting circuits based on picoseconds switching, i.e. THz oscillating, Josephson tunnel junctions are expected to find a large domain of applications in spatial sub-millimeter wave and FIR detectors as well as in satellite based wideband signal and data processors. In the first case SIS (superconductor-insulator-superconductor) tunnel junctions are required, while in the second case SNS (superconductor-normal metal-superconductor) self-shunted junctions are preferred. We present the advantages of the nitride junction technology currently developed at CEA-Grenoble, based on high-performance MTS (medium temperature superconductor) NbN films in both SIS and SNS junctions. In the SIS case the device performances rely on a sputter deposited and post-annealed, only 0.5-0.7 nm thick, dielectric MgO barrier. This leads to junctions with a Josephson critical current in the range of 10-25 kA/cm, and a large superconducting energy gap (> 5 meV) associated with a low sub-gap quasi-particle leakage current. These parameters are suitable for low “noise temperature ” heterodyne mixers, local oscillators, and integrated receivers in the 0.8 to 1.4 THz frequency range. In the SNS case, a new
To improve the performance of Josephson oscillators and SIS mixers over 700 GHz, we have developed a fabrication process to grow epitaxial NbN/MgO/NbN trilayers by reactive dc-sputtering. Trilayers were fabricated on a single-crystal MgO substrate at ambient temperature. NbN and MgO films were deposited by reactive dc-sputtering with an Nb and Mg target, respectively. The MgO inter-layer thickness was changed up to 480 nm, but, T/sub C/ and 20-K resistivity of the NbN upper-layer showed no remarkable dependency and they were 15.7 K and about 60 /spl mu//spl Omega/cm, respectively. To evaluate the RF performance of the epitaxial NbN films, we fabricated Josephson junctions with a microstrip resonator constructed from an epitaxial NbN/MgO/NbN trilayer. The I-V characteristics of the junction exhibited resonance steps up to 2.5 mV, which suggests that the epitaxial NbN films have low loss up to 1.2 THz.