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

Niイオン打込み層を介したNbN/Pbジョセフソン素子の特性

Yutaka Tanaka, Yukinori Saito, Shinji Suganomata

Published Jan 1, 1984• 0 citations
Publisher

Abstract

Superconductor-Normal-Superconductor (SNS) Josephson junctions were fabricated by ion implantation. The base electrode, NbN was prepared by reactive sputtering. After the NbN film surface was cleaned by Ar^+ ion (5.4keV), Ni^+ ion (16.2keV) was implanted. The doses of ion bombard the junction region were in the range of 1×10^<16>∿1×10^<17> ions/cm^2 for Ar^+ ion and 0.5×10^<15>∿1×10^<16> ions/cm^2 for Ni^+ ion. The counterelectrode was Pb. Current-voltage characteristics of the junctions subjected to the microwave radiation were measured. The junctions exhibited the well-defined ac Josephson steps, the best of which can show microwave induced Josephson steps up to 0.6mV. The magnetic field dependence of the maximum dc Josephson current was measured and found to be simillar to that of dc SQUID.

DOI
10.34429/00001825

Related papers

Microwave Characteristics of NbN/NbNx/NbN Josephson Junctions for Quantum Voltage Standards

Hirotake Yamamori, Akira Shoji

All NbN Josephson junctions with polycrystalline NbN films for both electrodes and barriers have been fabricated and their microwave characteristics for a quantum voltage standard were investigated. A superconductor and a normal metal were prepared by changing the partial pressure of N2during the rf sputter deposition of NbN films. For the Josephson junctions normal resistance was controlled by changing the partial pressure of N2during the NbNxbarrier deposition, and critical current was controlled by changing barrier thickness. As a result, it was found that the product of current and normal resistance can be optimized to maximize the current range of the constant-voltage step for quantum voltage standards.

Japanese Journal of Applied Physics•Oct 1, 2005•3 citations

Planar SNS Josephson junctions using multilayer Bi system

Kentaro Setsune, Koichi Mizuno, Hidetaka Higashino +1 more

Planar S/N/S Josephson junctions were successfully fabricated by multi-layered thin films of Bi-based high-Tc oxide superconductors. Two Bi2Sr2Ca1Cu2O(x) films and Bi2Sr2Cu1O(y) film were successively layered as superconducting electrodes and normal conducting buffer layer, respectively. These films were epitaxially deposited on (100) MgO substrate by in situ process of RF magnetron sputtering. Microjunction areas were defined by photolithography and Ar ion milling. These S/N/S type junctions clearly exhibited the AC Josephson effect under the irradiation of radio frequency waves of 12 GHz. More than 20th Shapiro steps were observed and those step heights were oscillated according to the irradiation power. These characteristics were stable and reproducible for different configuration of function area.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Mar 1, 1991•1 citation

Microwave-Induced Characteristics of ${({\rm NbN/TiN}_{\rm x})}_{N}/{\rm NbN}$ StackedJosephson Junction Arrays

Nobuko Koda, Alexandre Shoji, Hirotake Yamamori +1 more

Stacked (NbN/TiNx)N/NbN (N = 2, 3, 4, 5 and 10) Josephson junctions and their arrays have been fabricated on a Si chip and their microwave-induced characteristics were measured at a temperature around 10 K. To achieve a vertical and smooth edge of an NbN - TiNxmultilayer, an inductively coupled plasma reactive ion etching (ICP-RIE) technique was used. Current-voltage characteristics measured for stacks of (NbN/TiNx)N/NbN Josephson junctions without microwave indicated that critical currents for those junctions distribute in a certain range. We defined Ic- spread as (IcMAX- IcMIN)/IcAverage to measure the distribution of Ic. The Ic- spread was minimized when the thickness of intermediate electrodes was d = 50 nm. We also evaluated values of Ic- spread for stacks prepared at different fabrication runs as a function of the number of junctions in a stack N. As a result, we found N = 3 is the maximum for practical use. For arrays, we obtained a constant-voltage step height of about 2 m A for 2 048 stacks of double-barrier junctions (N = 2), and about 1 mA for 1 024 stacks of triple-barrier junctions (N = 3).

IEEE Transactions on Applied Superconductivity•Jun 1, 2009•2 citations

New fabrication process for Josephson tunnel junctions with (niobium nitride, niobium) double-layered electrodes

Akira Shoji, Fujitoshi Shinoki, S. Kosaka +2 more

All hard Josephson tunnel junctions, whose base and counter electrodes are composed of double-layered niobium nitride (NbN) and niobium (Nb) films, have been successfully fabricated by isolating a junction sandwich formed on a whole silicon wafer with a reactive ion etching technique. The reactive ion etching technique has been used for patterning both base and counterelectrodes, and self-aligning definition of junction areas has been performed. The fabricated junctions show good quality single-particle tunneling characteristics and excellent uniformity in critical currents.

Applied Physics Letters•Dec 1, 1982•70 citations

Stacked SNS Josephson junction arrays for quantum voltage standards

Paul D. Dresselhaus, Yonuk Chong, J. H. Plantenberg +1 more

NIST is using and developing superconductor-normal metal-superconductor (SNS) Josephson arrays for both programmable DC and AC voltage standards. Increasing the output voltage is difficult because the output voltage per junction is small; hence series arrays with large numbers of junctions are needed. The best way to generate higher voltages and achieve the best operating margins for the broadband drive signals is by densely packing the junctions into shorter arrays. NIST has been working on stacked SNS junctions to achieve this goal. By stacking junctions in the array, more junctions may be placed per length, while preserving a lumped microwave element. In this paper we introduce our results on stacked SNS junctions using MoSi/sub 2/ and Ti as barrier materials. These barriers were chosen because they can be reactive-ion etched (RIE) in contrast to our standard PdAu barriers, which must be wet etched. Using RIE, alternating layers of barrier material and Nb may be etched in a single step. We indirectly quantify the junction uniformity in the arrays by measuring the current range of the constant-voltage steps when the arrays are biased with a microwave drive.

IEEE Transactions on Applied Superconductivity•Jun 1, 2003•36 citations

SNS junction on Nb-Ti base for microwave circuits

M. Schubert, Ludwig Fritzsch, G. Wende +1 more

Superconductor-normal metal-superconductor (SNS) junctions are well-suited for large-scale integrated superconducting circuits. Potential applications are programmable voltage standards, digital-to-analog converters and large-scale RSFQ circuits. The application of SNS junctions provides some advantages, e.g. a simplified fabrication technology and reduced parasitic inductances. But it requires a technological process with dimensions down to the submicrometer region to achieve sufficiently high characteristic voltages I/sub C/R/sub N/. In our process the normal metal interlayer is titanium. Therefore the sidewall insulation of the junctions can be made by anodization, as it is known from the Nb-Al technology. Nb-Ti-Nb Josephson junctions and junction arrays were fabricated down to the submicrometer range with I/sub C/R/sub N/ values up to 87 microvolt depending on the titanium thickness. Their measured critical currents have a small spread of about 10 percent. Shapiro steps are observed under the influence of microwave irradiation. For the application of such junctions in a programmable Josephson voltage standard a new type of microwave circuit using coplanar strips is proposed and successfully tested in 10 V SIS circuits.

IEEE Transactions on Applied Superconductivity•Mar 1, 2001•12 citations
Superconductor-Normal-Superconductor (SNS) Josephson junctions were fabricated by ion implantation. The base electrode, NbN was prepared by reactive sputtering. After the NbN film surface was cleaned by Ar^+ ion (5.4keV), Ni^+ ion (16.2keV) was implanted. The doses of ion bombard the junction region were in the range of 1×10^<16>∿1×10^<17> ions/cm^2 for Ar^+ ion and 0.5×10^<15>∿1×10^<16> ions/cm^2 for Ni^+ ion. The counterelectrode was Pb. Current-voltage characteristics of the junctions subjected to the microwave radiation were measured. The junctions exhibited the well-defined ac Josephson steps, the best of which can show microwave induced Josephson steps up to 0.6mV. The magnetic field dependence of the maximum dc Josephson current was measured and found to be simillar to that of dc SQUID.
All NbN Josephson junctions with polycrystalline NbN films for both electrodes and barriers have been fabricated and their microwave characteristics for a quantum voltage standard were investigated. A superconductor and a normal metal were prepared by changing the partial pressure of N2during the rf sputter deposition of NbN films. For the Josephson junctions normal resistance was controlled by changing the partial pressure of N2during the NbNxbarrier deposition, and critical current was controlled by changing barrier thickness. As a result, it was found that the product of current and normal resistance can be optimized to maximize the current range of the constant-voltage step for quantum voltage standards.
Planar S/N/S Josephson junctions were successfully fabricated by multi-layered thin films of Bi-based high-Tc oxide superconductors. Two Bi2Sr2Ca1Cu2O(x) films and Bi2Sr2Cu1O(y) film were successively layered as superconducting electrodes and normal conducting buffer layer, respectively. These films were epitaxially deposited on (100) MgO substrate by in situ process of RF magnetron sputtering. Microjunction areas were defined by photolithography and Ar ion milling. These S/N/S type junctions clearly exhibited the AC Josephson effect under the irradiation of radio frequency waves of 12 GHz. More than 20th Shapiro steps were observed and those step heights were oscillated according to the irradiation power. These characteristics were stable and reproducible for different configuration of function area.
Microwave-Induced Characteristics of (NbN/TiNx)N/NbN{({\rm NbN/TiN}_{\rm x})}_{N}/{\rm NbN}(NbN/TiNx​)N​/NbN StackedJosephson Junction Arrays
Stacked (NbN/TiNx)N/NbN (N = 2, 3, 4, 5 and 10) Josephson junctions and their arrays have been fabricated on a Si chip and their microwave-induced characteristics were measured at a temperature around 10 K. To achieve a vertical and smooth edge of an NbN - TiNxmultilayer, an inductively coupled plasma reactive ion etching (ICP-RIE) technique was used. Current-voltage characteristics measured for stacks of (NbN/TiNx)N/NbN Josephson junctions without microwave indicated that critical currents for those junctions distribute in a certain range. We defined Ic- spread as (IcMAX- IcMIN)/IcAverage to measure the distribution of Ic. The Ic- spread was minimized when the thickness of intermediate electrodes was d = 50 nm. We also evaluated values of Ic- spread for stacks prepared at different fabrication runs as a function of the number of junctions in a stack N. As a result, we found N = 3 is the maximum for practical use. For arrays, we obtained a constant-voltage step height of about 2 m A for 2 048 stacks of double-barrier junctions (N = 2), and about 1 mA for 1 024 stacks of triple-barrier junctions (N = 3).
All hard Josephson tunnel junctions, whose base and counter electrodes are composed of double-layered niobium nitride (NbN) and niobium (Nb) films, have been successfully fabricated by isolating a junction sandwich formed on a whole silicon wafer with a reactive ion etching technique. The reactive ion etching technique has been used for patterning both base and counterelectrodes, and self-aligning definition of junction areas has been performed. The fabricated junctions show good quality single-particle tunneling characteristics and excellent uniformity in critical currents.
NIST is using and developing superconductor-normal metal-superconductor (SNS) Josephson arrays for both programmable DC and AC voltage standards. Increasing the output voltage is difficult because the output voltage per junction is small; hence series arrays with large numbers of junctions are needed. The best way to generate higher voltages and achieve the best operating margins for the broadband drive signals is by densely packing the junctions into shorter arrays. NIST has been working on stacked SNS junctions to achieve this goal. By stacking junctions in the array, more junctions may be placed per length, while preserving a lumped microwave element. In this paper we introduce our results on stacked SNS junctions using MoSi/sub 2/ and Ti as barrier materials. These barriers were chosen because they can be reactive-ion etched (RIE) in contrast to our standard PdAu barriers, which must be wet etched. Using RIE, alternating layers of barrier material and Nb may be etched in a single step. We indirectly quantify the junction uniformity in the arrays by measuring the current range of the constant-voltage steps when the arrays are biased with a microwave drive.
Superconductor-normal metal-superconductor (SNS) junctions are well-suited for large-scale integrated superconducting circuits. Potential applications are programmable voltage standards, digital-to-analog converters and large-scale RSFQ circuits. The application of SNS junctions provides some advantages, e.g. a simplified fabrication technology and reduced parasitic inductances. But it requires a technological process with dimensions down to the submicrometer region to achieve sufficiently high characteristic voltages I/sub C/R/sub N/. In our process the normal metal interlayer is titanium. Therefore the sidewall insulation of the junctions can be made by anodization, as it is known from the Nb-Al technology. Nb-Ti-Nb Josephson junctions and junction arrays were fabricated down to the submicrometer range with I/sub C/R/sub N/ values up to 87 microvolt depending on the titanium thickness. Their measured critical currents have a small spread of about 10 percent. Shapiro steps are observed under the influence of microwave irradiation. For the application of such junctions in a programmable Josephson voltage standard a new type of microwave circuit using coplanar strips is proposed and successfully tested in 10 V SIS circuits.