Pascal Febvre

Université Savoie Mont Blanc | UdS · IMEP-LAHC Institute of Microelectronics, Electromagnetism and Photonics

Superconductor electronics is gaining traction as the increasing density of integration of recent and future digital circuits pushes the limits of available simulation models. Designers often make assumptions in the behavioral models of circuit elements when simulating circuits. For instance high-frequency effects have been neglected so far in the...

Despite the many advantages of Single-Flux Quantum (SFQ) circuits, the low output voltage amplitude and high speed of output at cryogenic temperature is difficult to interface with standard electronics. State-of-the-art low-noise wide-band amplifiers are required to interface with room temperature electronics. One solution is to place preamplifiers...

Bias lines routed over a ground plane naturally form microstrip lines associated with the presence of a capacitance. This can lead to unwanted resonances when coupled to Josephson junctions. This work presents an electrical model of a shunted Josephson junction with its bias lines and pads, fabricated with the 1 kA/cm $^2$ RSFQ niobium process of...

We start with a short look at the problem of low-capacitance Josephson junctions, its history, and actual state-of-the-art. It is argued that such devices are important for applications requiring nonhysteretic current-voltage characteristics since reduction of capacitance by several times makes it possible to increase the device resistance by the s...

The Josephson effect, as an example of a macroscopic quantum phenomenon, reveals itself in the three-layer heterostructures formed by two superconductors coupled by a weak link that usually consists of a 1–2 nm-thick insulating barrier. The traditional way of modelling such-systems’ dynamics is based on an equivalent circuit that comprises three pa...

Single flux quantum (SFQ) based circuits are the subject of renewed attention due to their high speed and their very high energy efficiency. However, the need of cryogenic temperature, the complex physics of Josephson junctions and the lack of proper EDA tools causes slow progress in the field of superconducting electronics. In this work we introdu...

MoRe–Si(W)–MoRe planar Josephson junctions with a hybrid barrier layer made of amorphous silicon doped with tungsten at relatively high tungsten concentrations (~ 11%) are experimentally studied. Small intrinsic (natural) capacitance and shunting by tungsten nanoclusters give an advantage to MoRe–Si(W)–MoRe junctions against traditional superconduc...

Bias lines routed over a ground plane naturally form microstrip lines associated with the presence of a capacitance. This can lead to unwanted resonances when coupled to Josephson junctions. This work presents an electrical model of a shunted Josephson junction with its bias lines and pads, fabricated with the 1 kA/cm$^2$ RSFQ niobium process of th...

Single flux quantum (SFQ) based circuits are the subject of renewed attention due to their high speed and their very high energy efficiency. However, the need of cryogenic temperature, the complex physics of Josephson junctions and the lack of proper EDA tools causes slow progress in the field. Of superconducting electronics. In this work we introd...

Penetration of spin-polarized charges from a nearby ferromagnetic metallic layer into 100-μm-wide superconducting films of Pb and Mo–Re alloy with similar critical parameters but quite different spin-orbit coupling strengths is studied. It is shown that the diffusion of magnetic properties into a nearby superconductor can be employed as an electric...

The IARPA SuperTools program requires the devel-opment of superconducting electronic design automation (S-EDA) and superconducting technology computer aided design (S-TCAD) tools aimed at enabling the reliable design of complex superconduct-ing digital circuits with millions of Josephson junctions. Within the SuperTools program, the ColdFlux projec...

Thin-film hybrid heterostructures formed by superconducting molybdenum-rhenium-alloy films with a critical temperature of about 9 K and nanoscale silicon-based semiconducting interlayers with metallic tungsten nanorods have been fabricated and studied. Current-voltage characteristics of the junctions were measured at 4.2 K and under influence of 11...

We designed, fabricated and measured short one-dimensional arrays of masked ion-irradiated YBa2Cu3O7 Josephson junctions embedded into log-periodic spiral antennas. They consist of four or eight junctions separated either by 960nm or 80nm long areas of pristine material. Large spacing arrays show 'giant' Shapiro steps in the hundreds-GHz band at 66...

Emergence of phase-slip lines is one of the main mechanisms for dissipation in current-carrying superconducting thin films with lateral dimensions larger than the superconducting coherence length. We show that effective control of the wide resistive region between dissipation-free and completely ohmic transport regime can be achieved by evaporating...

We present a magnetic field model that shows how single flux quantum (SFQ)-based electronics can be affected by nearby current carrying strip lines and other external magnetic field sources. This work is an enabling step towards the design of SFQ circuits that can operate without the need for ferromagnetic shielding. Firstly, a specific 3-D coil sy...

The operating margins of unshielded SFQ circuits are influenced by external magnetic fields, and earlier research showed experimental results of operating region versus bias current for circuits with in-plane and perpendicularly applied magnetic fields. Here, we report a method that can be used to analyze shields to protect SFQ circuits from extern...

Single-Flux-Quantum (SFQ) digital circuits are mostly based on cells which rely on reliable foundary processes that make use of a superconducting ground plane as a reference for the active elements and the microstrip line interconnects. The quantum of magnetic flux h=2e, associated to the binary information, corresponds to a magnetic field energy d...

We designed, fabricated and tested short one dimensional arrays of masked ion-irradiated YBa$_2$Cu$_3$O$_7$ Josephson junctions (JJ) embedded into log-periodic spiral antennas. Our arrays consist of 4 or 8 junctions separated either by 960~nm or 80~nm long areas of undamaged YBCO. Samples with distanced junctions and with closely spaced junctions s...

This work presents the design, simulations and measurements of a compact 18×12 mm 2 monopole antenna fabricated on 1.6 mm-thick FR4 substrate for ultra-wideband (UWB) applications. The antenna exhibits a measured voltage standing wave ratio lower than 2 through the 3.1–10.9 GHz frequency range. The Wireless Baseband Transmission (WBT) scheme has be...

https://www.anses.fr/fr/system/files/AP2012SA0036Ra.pdf

An Antipodal Vivaldi Antenna (AVA) with a reduced size of 37mm x 21mm has been designed, simulated and fabricated on 1.6 mm-thick FR4 substrate for ultra-wideband (UWB) applications. It is customized with a slot resonator located on the ground plane only and with a shift of the ground plane input. AVA simulations and measurements are presented and...

The article contains sections titled:

FLUXONICS white paper - A special edition of the FLUXONICS newsletter - Authors : P. Febvre, C.J. Fourie, C. Granata, J. Kohlmann, J. Kunert, N. de Leo, M. Siegel, H. Toepfer, G. Waysand, S. Wuensch - Edited for the FLUXONICS Society

Following the ever-rising demand for new functionalities and novel materials in superconducting circuitry, we provide a complete view on the self-shunting problem in Josephson junctions, relating it to specific features of a multichannel weak link between electrodes where averaging over the channels yields a bimodal distribution of transparencies w...

An on-chip magnetic shielding technique was characterized on several DC-SQUIDs to prepare the next generation of complex digital RSFQ circuits designed by the FLUXONICS foundry. The maximal frequency of operation of a toggle flip-flop cell was used as a criteria to validate the concept. It goes from a simulated value of 52 GHz (46 2 GHz experimenta...

We report on the noise properties of ion-irradiated YBa2Cu3O7 Josephson junctions. This work aims at investigating the linewidth of the Josephson oscillation with a detector response experiment at 132 GHz. Experimental results are compared with a simple analytical model based on the Likharev–Semenov equation and the de Gennes dirty limit approximat...

There have been three great movements in the development of the Josephson digital logic: latching logic, single flux quantum (SFQ) logic, and low-energy logic. This chapter introduces the basic principles of the implementation of samplers and analog-to-digital converters (ADC) devices with superconductors. Furthermore, it addresses the recent state...

We report on an experimental and theoretical study of the high-frequency mixing properties of ion-irradiated YBa2Cu3O7 Josephson junctions embedded in THz antennas. We investigated the influence of the local oscillator power and frequency on the device performances. The experimental data are compared with theoretical predictions of the general thre...

We report on an experimental and theoretical study of the high-frequency mixing properties of ion-irradiated YBa2Cu3O7 Josephson junctions embedded in THz antennas. We investigated the influence of the local oscillator power and frequency on the device performances. The experimental data are compared with theoretical predictions of the general thre...

Cosmic microwave background (CMB) studies require observations in several frequency bands simultaneously. For example, the detection of clusters of remote galaxies can be performed by comparing CMB photon fluxes at different frequencies, using the spectral deformation of the Planck law, due to the Sunyaev-Zeldovich effect. We propose a single pixel...

This paper presents the design of a compact frontend diplexer for radio-astronomy applications based on a self complementary Bow-tie antenna, a 3 dB T-junction splitter and two pass-band fractal filters. The whole diplexer structure has been optimized by using an evolutionary algorithm. In particular the problem of the diplexer design is recast int...

There is universal agreement between the United Nations and governments from the richest to the poorest nations that humanity faces unprecedented global challenges relating to sustainable energy, clean water, low-emission transportation, coping with climate change and natural disasters, and reclaiming use of land. We have invited researchers from a...

The fluxgate magnetometer has long been the standard instrument of magnetic observatories due to its ease of use and sensitivity in the nanotesla range. Recently more sensitive magnetic sensors have become a requirement to study in particular the interaction between earthquakes and the ionosphere. The Superconducting QUantum Interference Device (SQ...

The fluxgate magnetometer has long been the standard instrument of magnetic observatories due to its ease of use and sensitivity in the nanotesla range. Recently more sensitive magnetic sensors have become a requirement to study in particular the interaction between earthquakes and the ionosphere. The Superconducting QUantum Interference Device (SQ...

A method has been developped to take into account the presence of a local external magnetic field in Superconducting Quantum Interference Devices (SQUIDs) loops composing Rapid Single-Flux-Quantum (RSFQ) circuits, through modifications of circuit inductances. A good agreement is observed between analytical formulas and simulations performed by time...

Low-T-c rapid single flux quantum (RSFQ) digital circuits without magnetic shielding fabricated with the FLUXONICS Foundry have been studied in the presence of external magnetic fields. Magnetic fields parallel to the plane of the chip are shown to influence more drastically the nominal behavior of the circuits above 5 mu T, while perpendicular mag...

We have investigated the electrodynamic properties of high-Tc Josephson junctions (JJs) and striplines made by ion irradiation in order to evaluate the potential of such a technology for low-power rapid single flux quantum superconductor digital electronics. The process is briefly presented, together with the JJ characteristics in the context of hi...

An interesting feature of Superconductor–Normal metal–Superconductor Josephson junctions for digital applications is due to their non-hysteretic current–voltage characteristics in a broad temperature range below Tc. This allows to design Single-Flux-Quantum (SFQ) cells without the need of external shunts. Two advantages can be drawn from this prope...

In this letter, we present the study of the high-frequency mixing properties of ion irradiated YBa2Cu3O7 Josephson nano-junctions. The frequency range, spanning above and below the characteristic frequencies fc of the junctions, permits clear observation of the transition between two mixing regimes. The experimental conversion gain was found to be...

This work presents the results of the synthesis of a light-weight inexpensive reconfigurable planar array antenna. The antenna structure is based on four circular patches. The sources points and some discontinuities on the patches can be electronically reconfigured by means of radio-frequency (RF) switches in order to modify the radiation pattern....

This paper presents the design, simulation of performance, and layout of a one-bit comparator for a pipeline analog-to-digital converter. It has been designed for the low critical temperature technology of the European Fluxonics Foundry and the part excluding the digital readout has been fabricated. Simulation shows that the incoming signal amplitu...

We have carried out a series of magnetic field measurements using a portable three-axis SQUID magnetometer at the Laboratoire Souterrain à Bas Bruit (LSBB), Rustrel, France. The magnetometer was originally developed as part of the cryoEDM neutron electric dipole moment experiment [1], where we need to monitor drifts in the magnetic field at a level...

For four decades semiconductor electronics has followed Moore’s law: with each generation of integration the circuit features became smaller, more complex and faster. This development is now reaching a wall so that smaller is no longer any faster. The clock rate has saturated at about 3–5 GHz and the parallel processor approach will soon reach its...

We have investigated the electrodynamic properties of High-Tc strip-lines made by ion irradiation, in order to evaluate the potentialities of such a technology for RSFQ superconductor digital electronic. SQUID loops of different length and width have been fabricated by ion bombardment of 70 nm thick films through e-beam lithographied shadow masks,...

We have demonstrated superconductor-normal metal-insulator-superconductor Nb / Al – AlO _X/ Nb Josephson junctions developed with Al layer thicknesses between 30 and 100 nm, resulting in nonhysteretic current-voltage characteristics for critical current densities between 20 and 60 kA / cm ² . Specific capacitances ranged from...

Superconducting Quantum Interference Devices (SQUIDs) are known to be the most sensitive magnetometers, used in a wide range of applications like biomagnetism, geomagnetism, Non Destructive Evaluation (NDE), metrology or fundamental science. For all these applications, the SQUID sensor is used in analog mode and associated with a carefully designed...

We present a compact design of a slot bow-tie antenna excited by a microstrip to coplanar waveguide (CPW) transition, operating at the central frequency of 45 GHz in the millimeter wave range from 25 to 65 GHz. Simulation results have shown 85% bandwidth with VSWR < 2 for this antenna. Its small size and symmetric geometry facilitate the integratio...

The rapid single flux quantum electronics is characterized by a low switching energy, which makes it susceptible to noise introduced bit-errors. For industrial applications a certain noise immunity is required which is still a challenge especially for circuits of higher complexity. We analysed the influence of each individual resistor in a toggle f...

We present a new kind of rapid-single-flux-quantum (RSFQ) output driver together with a pseudomorphic high electron mobility transistor (p-HEMT) amplifier both operating at liquid helium temperature. The passive interconnect including the interchip connection between the RSFQ output driver and the first transistor stage of the semiconductor amplifi...

Digital superconducting quantum interference devices (SQUIDs) have been proposed to extend the dynamic range of analog SQUIDs whenever magnetic fields varying in a wide range need to be measured. We developed a digital SQUID concept, based on the single flux quantum technique, using the reliable 1 kA / cm ² niobium trilayer technology of...

We propose a pixel design, aimed to be included in an array, receiving and de- tecting simultaneously two bands of the Cosmic Microwave Background (CMB). It is composed of a bowtie antenna, feeding a diplexer structure to separate the signal towards two bolomet- ric detectors at 150 and 220 GHz. The diplexer makes use of differential transmission l...

This paper investigates the influence of external field on the distribution of the critical current of Josephson junctions. The external field can cause trapped flux which may reduce the critical current. Experimental results show a formation of bunches in the distribution of the critical current when the external magnetic field rises a certain lim...

Sets of bow-tie antennas, used in a single emitter-receiver near-field configuration and in array configuration, have been studied to be used as wireless means to transmit 8–12GHz microwave signals from the cold stage of a cryogenic system to a room-temperature processing unit. Indeed, the absence of heat conduction allows increasing the performanc...

Superconductive rapid single-flux-quantum (RSFQ) circuits are able to work in a digital mode with clock frequencies of tens to hundreds of GHz. They rely on shunted Josephson junctions assembled with thin films inductors. To date, there is no on-the-shelf instrumentation apparatus which allows to directly verify the digital operation of such circui...

Printed bow-tie antennas have been designed to operate in X-band in near-field configuration in order to transmit signals over very short distances for cryogenic applications. Transmission between two bow-tie antennas directly placed across from each other has been simulated and measured for different configurations. It is shown that, by placing ba...

This paper deals with the study of metal–semiconductor–metal (MSM) photodetectors used for time-resolved detection of low amplitude picosecond-range signals, such as rapid single flux quantum (RSFQ) pulses (Likharev and Semenov 1991 IEEE Trans. Appl. Supercond. 1 3–27) generated by superconductive electronic circuits. A typical 6 ps wide incoming R...

The roadmap gives an overview on status and future developments in Superconducting Digital Electronics (SDE). Key areas in SDE under focus are applications, circuit simulation and design, circuit fabrication, interfacing and testing, cooling and system aspects, and new devices and materials. Care was taken to establish the vital link between resear...

Rapid-Single-Flux-Quantum (RSFQ) digital circuits based on shunted Josephson junctions have been shown to be able to digitally process signals up to several hundreds GHz. The principle of operation is based on the generation, transport and processing of picosecond voltage pulses of 2.07 mV.ps quantized area, which corresponds to one quantum flux h/...

Superconductive microwave rapid single-flux-quantum (RSFQ) digital circuits offer the possibility to digitally process signals in the frequency range of tens of GHz. An example of application to bring the advantages of this technology deals with digital SQUIDs, used for sensitive magnetometry with a broadband dynamics connected to a slew-rate in th...

The application of superconducting rapid single-flux quantum (RSFQ) digital electronics for highly sensitive measurement of magnetic fields can provide significant advantages in the use of conventional analogue SQUIDs, especially in terms of operation speed and dynamic range. Furthermore, utilizing an unconventional generalized single-flux-quantum...

A set of standard rapid-single-flux-quantum logic cells has been established in order to build blocks for complex high-speed superconducting digital applications. Special emphasis has been put on the implementation with Nb and NbN technologies as well as with high-Tc superconductors. The influence of the different technological parameters on the pr...

Nitride superconductors and specially niobium nitride are key materials for developing high performance optoelectronic and digital circuits. We are presenting a way to achieve such high frequency devices on R-plane sapphire or MgO substrates. Deposition of thin and flat NbN films with Te above 10 K, low and reproducible penetration depth ( L 250 nm...

A new NbN multilayer technology has been developed on 3 inch diameter R-plane sapphire substrates, for combining on-chip fast RSFQ circuits with GHz bandwidth optical links, The circuits take advantage of two high quality (110) NbN layers sputtered epitaxially on sapphire at 600°C and selectively patterned: a 400 nm thick layer (λ _L~250...

Hilbert Transform spectroscopy is described as a method to analyze the spectrum of pulse trains generated by RSFQ circuits. Simulations are carried out using parameters appropriate for NbN Josephson junctions for both generation and detection of SFQ pulse trains. It is shown that the pulse shape along with the pulse train repetition rate can be ext...

A Swedish–French submillimeter telescope consisting on a 60 cm diameter Cassegrain telescope with a liquid helium cooled supraconductor–isolator–supraconductor (SIS) heterodyne receiver flew on September 25th 1997 in the southwest of France. It was carried out by the Pointed InfraRed Observation Gondola (PIROG, 8th flight) to a ceiling altitude of...

NbN/MgO/NbN Josephson tunnel junctions and multilayers have been achieved on 3 inch. Si and SOI substrates in order to develop high-speed RSFQ logic gates with terahertz cut-off frequency junctions and high operating temperature (10 K). Small area junctions (∼1 μm2) with 20 kA/cm2JC and low sub-gap leakage current (Vm>15 mV) at 4.2 K (and JC∼10 kA/...

We report and discuss here the final results of two experiments both devoted to the search of O2 in the Milky Way. 1) a ground-based search with the POM-2 telescope (Castets et al. 1988) of the rare 16O18O isotopomer using the atmospherically unblocked NJ 21 - 01 transition at 234 GHz (Maréchal et al. 1997a). 2) a balloon-borne search consisting of...

A process of trilayer deposition to obtain small Nb/Al-AlOx/Nb junctions (1 mu m2) with excellent I-V characteristics, good reliability and high current densities is described. To optimize this process, it has been useful to carry out several studies. The authors found that it was necessary to heat sink the quartz substrate during all trilayer fabr...

Using a balloon-borne 60 cm telescope equipped with an SIS receiver we have searched for the 425 GHz molecular oxygen line in the NGC7538 and the W51 regions. The experiment was technically successful (confirmed by the detection of the (13) CO (4-3) line at 440 GHz), but we failed to detect emission from molecular oxygen. The inferred upper limits...

Josephson currents have been observed to drain instabilities and decrease the sensitivity of a heterodyne superconductor-insulator-superconductor (SIS) receiver operated at submillimeter wavelengths. A static magnetic field is usually applied on the SIS junction to reduce the magnitude of its critical Josephson currents and enable quasiparticle mix...