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

International Conference on Solid State Devices and Materials (SSDM)

Fabrication of Josephson Weak Links using Electron Beam Lithography and Ion Etching and Proposal of a New Single Flux Quantum Logic

Hiroshi Tamura, Y. Okabe, T. Sugano

Published Aug 28, 1979• 0 citations
Publisher

Abstract

A new single flux quantum device is proposed, and, in conjunction with it, fabrication process of Josephson weak links using electron beam lithography and ion-etching is reported. Two types of niobium weak links, microbridges and thick-thin-thick type bridges, have been fabricated. They showed dc supercurrent, but microwave-induced steps were observed for thick-thin-thick type bridge only. The proposed logic device is constructed with a magnetically coupled rf-SQUID cells. These cells behave in the similar manner as Domino-toppling, and basic logic operations, AND, OR and NOT, are demonstrated by numerical calculations. Switching delay of about 10ps is expected to be practical.

DOI
10.7567/ssdm.1979.c-2-4

Related papers

Josephson single-flux-quantum logic circuits using niobium weak links

Hiroyuki Tamura, Yoji Okabe, T. Sugano

Josephson logic circuits using fluxoid quantization in a one-junction interferometer to represent logical states have been fabricated from thin films of Nb by means of photolithography, electron beam lithography, and reactive ion etching. A variable thickness bridge is used as a Josephson junction in the one-junction interferometer. The logic circuits have shown AND and OR logic functions.

Applied Physics Letters•Nov 1, 1981•16 citations

Weak link nanobridges as single flux quantum elements

Connor D. Shelly, Patrick See, Jane Ireland +2 more

This paper investigates the feasibility of using weak link nanobridges as Josephson junction elements for the purpose of creating Josephson circuits. We demonstrate the development of a single-step electron beam lithography procedure to fabricate niobium nanobridges with dimensions down to . The single-step process facilitates fabrication that is scalable to complex circuits that require many junctions. We measure the IV -characteristics (IVC) of the nanobridges between temperatures of and and find agreement with numerical simulations and the analytical resistively shunted junction (RSJ) model. Furthermore, we investigate the behaviour of the nanobridges under rf irradiation and observe the characteristic microwave-induced Shapiro steps. Our simulated IVC under rf irradiation using both the RSJ model and circuit simulator JSIM are in agreement with the experimental data. As a potential use of nanobridges in circuits requiring many junctions, we investigate the theoretical performance of a nanobridge-based Josephson comparator circuit using JSIM .

Superconductor Science and Technology•Jul 19, 2017•15 citations

Properties of superconducting weak links prepared by ion implantation and by electron beam lithography

E. P. Harris, Robert B. Laibowitz

In this paper, we present our latest results on the properties of superconducting weak links prepared in Mo films by ion-implantation and in Nb films by electron-beam lithography. In the case of the ion-implanted weak links, which structurally resemble proximity-effect bridges, we find that the static properties are quite well described by a recent theory of Likharev and Yakobson. We further find that the rf response of these weak links is in excellent agreement with quasistatic resistively-shunted-junction model calculations based on a sinusoidal current-phase relation at those temperatures for which such a current-phase relation is predicted by the static theory of Likharev and Yakob-son. For the e-beam fabricated Nb bridges, which have the Dayem bridge geometry, our sample preparation techniques have allowed us to produce bridges and two-junction interferometers in which the link dimensions are as small as about 2000 Angstroms. We find that Josephson effects are observable in these bridges even when the bridge dimensions exceed the temperature-dependent coherence length by about an order of magnitude, but are still less than the effective thin-film penetration depth.

IEEE Transactions on Magnetics•Jan 1, 1977•20 citations

Fabrication of Niobium Nanobridge Josephson Junctions

Takashi Tachiki, Kenji Horiguchi, Takashi Uchida

To realize antenna-coupled Josephson detectors for microwave and millimeter-wave radiation, planar-type Nb nanobridge Josephson junctions were fabricated. Nb thin films whose thickness, the root mean square roughness and the critical temperature were 20.0 nm, 0.109 nm and 8.4 K, respectively were deposited using a DC magnetron sputtering at a substrate temperature of 700°C. Nanobridges were obtained from the film using 80-kV electron beam lithography and reactive ion-beam etching in CF 4 (90%) + O2 (10%) gases. The minimum bridge area was 65 nm wide and 60 nm long. For the nanobridge whose width and length were less than 110 nm, an I-V characteristic showed resistively-shunted-junction behaviour near the critical temperature. Moreover, Shapiro steps were observed in the nanobridge with microwave irradiation at a frequency of 6 – 30 GHz. The Nb nanobridges can be used as detectors in the antenna-coupled devices.

Journal of Physics Conference Series•May 12, 2014•1 citation

Proposal of single-flux-quantum logic device

Hiroyuki Tamura, Yoji Okabe, T. Sugano

A new type of logic gate that can be designed using a nonhysteretic Josephson weak link is proposed. The basic component of the proposed device is a one-junction interferometer, and a logic state is represented by either a zero or a single-flux-quantum. In contrast to the "Parametric Quantron," this device is designed to operate without a three-phase clock and the dependence of the junction critical current on magnetic field is not used. The switching behavior of the device was simulated by computer and an analytical expression for the switching delay has been obtained.

IEEE Transactions on Electron Devices•Oct 1, 1980•14 citations

Development of Flux-Tuneable Inductive Nanobridge SQUIDs for Quantum Technology Applications

Laith Meti, George Long, Tom Godfrey +6 more

Niobium nanobridge SQUIDs have shown exceptional noise performance with potential applications in quantum information processing, weak signal detection and single spin detection where the nanobridge geometry should enable efficient electromagnetic coupling to implanted spins. Combining such devices with dispersive microwave readout circuitry allows the spin sensitivity to be further improved by overcoming the standard thermal limit. Here we report on the fabrication and dispersive microwave readout of an array of niobium nanobridge rf SQUIDs incorporated into a superconducting resonator, including the optimization of the nanobridge fabrication process by electron beam lithography. We show the measured flux-tuneability of the resonance is in good agreement with theory, and we also discuss how the nonlinearity of the weak-link in the resonator structure allows for the mediation of parametric effects to enhance performance.

IEEE Transactions on Applied Superconductivity•Feb 17, 2023•3 citations
A new single flux quantum device is proposed, and, in conjunction with it, fabrication process of Josephson weak links using electron beam lithography and ion-etching is reported. Two types of niobium weak links, microbridges and thick-thin-thick type bridges, have been fabricated. They showed dc supercurrent, but microwave-induced steps were observed for thick-thin-thick type bridge only. The proposed logic device is constructed with a magnetically coupled rf-SQUID cells. These cells behave in the similar manner as Domino-toppling, and basic logic operations, AND, OR and NOT, are demonstrated by numerical calculations. Switching delay of about 10ps is expected to be practical.
This paper investigates the feasibility of using weak link nanobridges as Josephson junction elements for the purpose of creating Josephson circuits. We demonstrate the development of a single-step electron beam lithography procedure to fabricate niobium nanobridges with dimensions down to . The single-step process facilitates fabrication that is scalable to complex circuits that require many junctions. We measure the IV -characteristics (IVC) of the nanobridges between temperatures of and and find agreement with numerical simulations and the analytical resistively shunted junction (RSJ) model. Furthermore, we investigate the behaviour of the nanobridges under rf irradiation and observe the characteristic microwave-induced Shapiro steps. Our simulated IVC under rf irradiation using both the RSJ model and circuit simulator JSIM are in agreement with the experimental data. As a potential use of nanobridges in circuits requiring many junctions, we investigate the theoretical performance of a nanobridge-based Josephson comparator circuit using JSIM .
In this paper, we present our latest results on the properties of superconducting weak links prepared in Mo films by ion-implantation and in Nb films by electron-beam lithography. In the case of the ion-implanted weak links, which structurally resemble proximity-effect bridges, we find that the static properties are quite well described by a recent theory of Likharev and Yakobson. We further find that the rf response of these weak links is in excellent agreement with quasistatic resistively-shunted-junction model calculations based on a sinusoidal current-phase relation at those temperatures for which such a current-phase relation is predicted by the static theory of Likharev and Yakob-son. For the e-beam fabricated Nb bridges, which have the Dayem bridge geometry, our sample preparation techniques have allowed us to produce bridges and two-junction interferometers in which the link dimensions are as small as about 2000 Angstroms. We find that Josephson effects are observable in these bridges even when the bridge dimensions exceed the temperature-dependent coherence length by about an order of magnitude, but are still less than the effective thin-film penetration depth.
To realize antenna-coupled Josephson detectors for microwave and millimeter-wave radiation, planar-type Nb nanobridge Josephson junctions were fabricated. Nb thin films whose thickness, the root mean square roughness and the critical temperature were 20.0 nm, 0.109 nm and 8.4 K, respectively were deposited using a DC magnetron sputtering at a substrate temperature of 700°C. Nanobridges were obtained from the film using 80-kV electron beam lithography and reactive ion-beam etching in CF 4 (90%) + O2 (10%) gases. The minimum bridge area was 65 nm wide and 60 nm long. For the nanobridge whose width and length were less than 110 nm, an I-V characteristic showed resistively-shunted-junction behaviour near the critical temperature. Moreover, Shapiro steps were observed in the nanobridge with microwave irradiation at a frequency of 6 – 30 GHz. The Nb nanobridges can be used as detectors in the antenna-coupled devices.
A new type of logic gate that can be designed using a nonhysteretic Josephson weak link is proposed. The basic component of the proposed device is a one-junction interferometer, and a logic state is represented by either a zero or a single-flux-quantum. In contrast to the "Parametric Quantron," this device is designed to operate without a three-phase clock and the dependence of the junction critical current on magnetic field is not used. The switching behavior of the device was simulated by computer and an analytical expression for the switching delay has been obtained.
Niobium nanobridge SQUIDs have shown exceptional noise performance with potential applications in quantum information processing, weak signal detection and single spin detection where the nanobridge geometry should enable efficient electromagnetic coupling to implanted spins. Combining such devices with dispersive microwave readout circuitry allows the spin sensitivity to be further improved by overcoming the standard thermal limit. Here we report on the fabrication and dispersive microwave readout of an array of niobium nanobridge rf SQUIDs incorporated into a superconducting resonator, including the optimization of the nanobridge fabrication process by electron beam lithography. We show the measured flux-tuneability of the resonance is in good agreement with theory, and we also discuss how the nonlinearity of the weak-link in the resonator structure allows for the mediation of parametric effects to enhance performance.