Fabrication and Logic Operation of Oxide SFQ-Circuit-Components

Tarutani, Y.; Ishimaru, Yoshihiro; Wakana, H.; Adachi, Seiji; Nakayama, Keiichi I.; Oshikubo, Y.; Horibe, Osami; Morimoto, Yoshihisa; Tanabe, K.

doi:10.1109/tasc.2005.849854

Cited by 21 publications

(5 citation statements)

References 10 publications

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“…5) We obtained sheet inductance values of 1.0 pH per square or less below 50 K for the base and counter electrode layers, which are small enough for operation of SFQ circuits. The interface-modified ramp-edge junctions fabricated on a superconducting ground plane exhibited a 1 spread in I c of approximately 8% for a 1000-junction series-array 6) and an I c R n product higher than 1 mV at 40 K. 7) We have also confirmed proper logic operation of some elementary SFQ circuits, [8][9][10] though the observed operating margins were substantially narrower than those expected from circuit simulations.…”

supporting

confidence: 56%

Improvement of Critical Current Density Uniformity for Interface-Modified Josephson Junctions in Single Flux Quantum Circuits

Wakana¹,

Adachi²,

Tarutani³

et al. 2006

jjap

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We present the results of ab initio electronic structure calculations for the adsorption characteristics of three amine molecules on Au(111), which show that the inclusion of van der Waals interactions between the isolated molecule and the surface leads in general to good agreement with experimental data on the binding energies. Each molecule, however, adsorbs with a small tilt angle (between −5 and 9 • ). For the specific case of 1,4-diaminobenzene (BDA) our calculations reproduce the larger tilt angle (close to 24 • ) measured by photoemission experiments, when intermolecular (van der Waals) interactions (for about 8% coverage) are included. These results point not only to the important contribution of van der Waals interactions to molecule-surface binding energy, but also that of intermolecular interactions, often considered secondary to that between the molecule and the surface, in determining the adsorption geometry and pattern formation.

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supporting

confidence: 56%

Improvement of Critical Current Density Uniformity for Interface-Modified Josephson Junctions in Single Flux Quantum Circuits

Wakana¹,

Adachi²,

Tarutani³

et al. 2006

jjap

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“…We tried to optimize the design of elementary SFQ circuits taking account of both thermal noise and variations due to spreads and/or a deviation of the operating temperature. Test circuits including a DC-SFQ converter, JTLs, a set-reset-type SFQ-DC converter [32], and various SFQ elements such as a confluence buffer, an RS-FF, a T-FF, and an inverter have been fabricated based on the above-mentioned HTS process, and their logic operations at low frequency have been confirmed at temperatures of 30-60 K. Moreover, long-JTL circuits with 100-200 JJs were successfully operated with finite bias-current margins [33].…”

Section: B Circuit Design and Operationmentioning

confidence: 99%

Recent Progress in SFQ Device Technologies in Japan

Tanabe

Hidaka

2007

IEEE Trans. Appl. Supercond.

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Recent progress in single flux quantum (SFQ) device technologies in Japan is described, mainly focusing on those developed in the NEDO "Superconductors Network Device Project" which includes developments of both LTS and HTS devices. The advanced Nb process which consists of a planarized structure with nine Nb layers and 10 kA cm 2 Josephson junctions (JJs) has been developed. This enables fabrication of chips including 100,000 JJs and operating frequency up to 80 GHz. We have also developed the CAD tool by which one can generate SFQ circuit layouts including about 400,000 JJs from logic descriptions. For demonstration of a small-scale switch system, a 4 4 switch chip, a 117 Gbps multichip-module (MCM) technology, and a packaging technology with 32-ch 10 Gbps I/Os to an MCM have been developed. By using the multilayer process with three HTS epitaxial layers and interfaceengineered ramp-edge JJs, we demonstrated operation of SFQ circuits with up to 200 JJs. A variety of elementary SFQ circuits such as a T-FF and a 1:2 switch required for an A/D converter front-end circuit have been designed based on a new layout method, and their operation at 30-50 K has been confirmed. A prototype sampler system is being developed for demonstration of bandwidth over 100 GHz for optical input signals.

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“…We have fabricated some elementary SFQ circuits by using the multilayer structures and junction processes mentioned above. A long Josephson transmission line (JTL) circuit with more than 100 Josephson junctions was found to work at temperatures up to 38 K [17] and a set-reset flip-flop circuit was operated at temperatures higher than 30 K [18]. We have recently succeeded in operating a toggle flip-flop [19], a confluence buffer [20] and other SFQ circuits such as a QOS comparator [21] and a sampler [22].…”

Section: Fabrication Of Sfq Circuitsmentioning

confidence: 99%

Fabrication of high-temperature superconductor single-flux-quantum circuits using a multilayer structure with a smooth surface

Wakana¹,

Adachi²,

Tsubone³

et al. 2006

Supercond. Sci. Technol.

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We have developed a multilayer structure with a smooth surface and fabrication processes for HTS single-flux-quantum (SFQ) circuits. The multilayer structure with surface roughness R a less than 2 nm, composed of a La 0.2 -Y 0.9 Ba 1.9 Cu 3 O x ground plane and base electrode layer, and SrSnO 3 insulating layers, was deposited by off-axis magnetron sputtering. We have fabricated interface-engineered junctions based on the multilayer structure using an La 0.2 -Yb 0.9 Ba 1.9 Cu 3 O x counter-electrode layer prepared by pulsed laser deposition. The fabricated junctions exhibited excellent Josephson characteristics with a 1-σ spread in I c as low as 8% for 1000 junctions. The sheet inductance values below 50 K were 0.8-1.0 pH per square. Operation of several elementary SFQ circuits including a toggle flip-flop, a confluence buffer, a set-reset flip-flop and other SFQ elements has been successfully demonstrated at 30-60 K.

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Fabrication and Logic Operation of Oxide SFQ-Circuit-Components

Cited by 21 publications

References 10 publications

Improvement of Critical Current Density Uniformity for Interface-Modified Josephson Junctions in Single Flux Quantum Circuits

Improvement of Critical Current Density Uniformity for Interface-Modified Josephson Junctions in Single Flux Quantum Circuits

Recent Progress in SFQ Device Technologies in Japan

Fabrication of high-temperature superconductor single-flux-quantum circuits using a multilayer structure with a smooth surface

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