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 Vacuum Science & Technology A Vacuum Surfaces and Films

Improved characteristics of mesa-type intrinsic Josephson junctions by vacuum cleavage process for Bi2Sr2CaCu2O8+δ/Au contacts

Hiroki Ishida, Takahiro Kato, Atsushi SAITO, Kanji Yasui

Published Apr 27, 2012• 1 citation
Publisher

Abstract

Improvement in the quality of stacked intrinsic Josephson junctions (IJJs) was attempted using Bi2Sr2CaCu2O8+δ (Bi-2212) single crystals. The introduction of a clean Bi-2212/Au interface reduced contact resistivity (ρc), decreased low frequency noise, and suppressed the drop in the maximum Josephson current (Ic), which are very important factors for applications such as a superconducting quantum interference device. The ρc of samples produced by crystal cleavage in air or vacuum were, respectively, 8.2 × 10−5 and 7.0 × 10−6 Ω cm2 at 300 K and 8.2 × 10−5 and 2.1 × 10−6 Ω cm2 at 77 K. Random-telegraph voltage noise observed with the air-cleaved samples did not occur for the samples cleaved in a vacuum. The degradation of Ic was suppressed for IJJs produced by the vacuum cleavage process.

DOI
10.1116/1.4707151

Related papers

Fabrication of Ultrasmall High-Quality Bi2Sr2CaCu2O8+δIntrinsic Josephson Junctions

Tetsuro Matsumoto, Hiromi Kashiwaya, Hajime Shibata +3 more

The fabrication of ultrasmall high-quality intrinsic Josephson junctions (IJJs) using a cuprate superconductor is critical for the realization of a qubit. We investigated the mechanism of damage induced by a Ga + beam in a Bi 2 Sr 2 CaCu 2 O 8+δ IJJ during focused ion beam (FIB) processing. On the basis of the results, we developed a process that allowed the successful fabrication of an ultrasmall and high-quality IJJ. The damage induced by the FIB is reduced by restricting the direction of the Ga + beam so that the junction area is not directly irradiated by the ion beam. The fabricated ultrasmall IJJ device has a junction area of 0.3 µm 2 and shows excellent current–voltage characteristics.

Applied Physics Express•Sep 19, 2008•5 citations

Measurements of low-frequency noise spectral densities for a small-sized stack of intrinsic Josephson junctions of Bi2Sr2CaCu2Oy single crystal

Atsushi SAITO, Hiroki Ishida, K. Hamasaki +2 more

We measured the low-frequency-voltage noise properties of a small-sized stack of intrinsic Josephson junctions formed on the surface of a cleaved Bi2Sr2CaCu2Oy (Bi-2212) single crystal, containing a few intrinsic Josephson junctions. A stack with an area of 2×2μm was fabricated by electron-beam lithography and argon-ion-milling. The current–voltage (I–V) characteristics along the c-axis direction of the stack were measured by a three-terminal method. The stack showed (I–V) and dV∕dI-V curves without backbending due to heating effects. Five discrete resistive branches with hysteresis were observed in the low-voltage region of these curves. The measured noise-voltage spectral density SV(f) had a 1∕f dependence on frequency. We estimated the magnitude of the 1∕f noise parameter η from SV(f) in a Bi-2212 stack and found that above the sum-gap voltage in a small-sized stack η was almost the same as that for low-Tc Nb∕Al+AlOx∕Nb high-quality tunnel junctions.

Applied Physics Letters•Aug 10, 2004•5 citations

Individual Shapiro steps observed in resistively shunted intrinsic Josephson junctions on Bi2Sr2CaCu2O8+x single crystals

H. B. Wang, Yuta Aruga, J. Chen +3 more

With a thin gold layer, we fabricated mesa-like shunted intrinsic Josephson junction stacks on Bi2Sr2CaCu2O8+x single crystals. Instead of the multibranch structure and large voltage jumps often observed in conventional intrinsic junctions, current–voltage characteristics typical of resistively shunted junctions were obtained. Individual Shapiro steps were clearly visible with irradiation at frequencies from a few to 20 GHz. The experiments demonstrated not only the ac Josephson effects directly but also the possibility of employing intrinsic Josephson junctions in high-frequency applications.

Applied Physics Letters•Aug 14, 2000•26 citations

Microwave responses of an insular intrinsic Josephson junction stack fabricated from Bi-Sr-Ca-Cu-O single crystal

H.B. Wang, Peiheng Wu, Takashi Yamashita

The conventional c-axis intrinsic Josephson junction (IJJ) stack is usually fabricated from a piece of single crystal in such a way that it looks like a small mesa sitting on a big pedestal. In some cases the effects of this pedestal should be taken into account in order to explain the experimental observations. To avoid this problem we have developed a novel technique by which we are able to remove a small sample from the single crystal and place it on a substrate with low microwave loss. This enable us to couple it to other microwave devices such as antenna etc. This small sample, or junction stack, measures a few micrometers by a few micrometers in the a-b plane and a few hundred angstroms along the c-axis and is plated with normal metal on both the top and the bottom. To distinguish the structure from the conventional one, we call it an insular intrinsic Josephson junction stack. We carefully study current-voltage characteristics, microwave responses, frequency mixing properties, and discuss the possible applications.

IEEE Transactions on Applied Superconductivity•Mar 1, 2001•10 citations

Zero-crossing steps in intrinsic Josephson junctions of Bi2Sr2CaCu2O8+δ

H. L. Johnson, Gerd Hechtfischer, Gabriel Götz +2 more

We have investigated the response to microwave irradiation of small mesas fabricated on single crystals of Bi2Sr2CaCu2O8+δ. We observe zero-crossing steps in the current-voltage characteristic which are consistent with the intrinsic Josephson junctions in the mesa stack phase-locking to the external microwave field.

Journal of Applied Physics•Jul 15, 1997•17 citations

Magnetic field dependence of micromachined Bi2Sr2CaCu2O8+δ intrinsic Josephson junctions with a submicron loop

S. J. Kim, J. Chen, Kenji Nakajima +3 more

Two-stacked intrinsic Josephson junctions (IJJs) on a Bi2Sr2CaCu2O8+δ(Bi-2212) whisker with a submicron hole are micromachined by a 3D focused ion beam (FIB) etching method. The junction area, the number of elementary junctions, and the loop area of the SQUIDs are 3, 20, and 0.42 μm2, respectively. The SQUIDs show typical I–V characteristics of IJJs with a critical current IC of 12 μA at 4.2 K. The modulation parameter βL(=2ICL/Φ0) is 6.4, and the inductance L of the SQUID is 1120 pH. That includes the inductances of the elementary junction around a SQUID loop. In a strong magnetic field, the Fraunhofer pattern is obtained and well fitted to the calculated value from the junction size, ΔB=Φ0/tW; t is the interlayer distance, and W is the junction width. In a low magnetic field, approximately 10% of the IC modulation corresponding to the value of βL is observed. Eighty G of the modulation period approximately agrees with the value calculated from the SQUID.

Journal of Applied Physics•May 15, 2002•19 citations
Improvement in the quality of stacked intrinsic Josephson junctions (IJJs) was attempted using Bi2Sr2CaCu2O8+δ (Bi-2212) single crystals. The introduction of a clean Bi-2212/Au interface reduced contact resistivity (ρc), decreased low frequency noise, and suppressed the drop in the maximum Josephson current (Ic), which are very important factors for applications such as a superconducting quantum interference device. The ρc of samples produced by crystal cleavage in air or vacuum were, respectively, 8.2 × 10−5 and 7.0 × 10−6 Ω cm2 at 300 K and 8.2 × 10−5 and 2.1 × 10−6 Ω cm2 at 77 K. Random-telegraph voltage noise observed with the air-cleaved samples did not occur for the samples cleaved in a vacuum. The degradation of Ic was suppressed for IJJs produced by the vacuum cleavage process.
The fabrication of ultrasmall high-quality intrinsic Josephson junctions (IJJs) using a cuprate superconductor is critical for the realization of a qubit. We investigated the mechanism of damage induced by a Ga + beam in a Bi 2 Sr 2 CaCu 2 O 8+δ IJJ during focused ion beam (FIB) processing. On the basis of the results, we developed a process that allowed the successful fabrication of an ultrasmall and high-quality IJJ. The damage induced by the FIB is reduced by restricting the direction of the Ga + beam so that the junction area is not directly irradiated by the ion beam. The fabricated ultrasmall IJJ device has a junction area of 0.3 µm 2 and shows excellent current–voltage characteristics.
We measured the low-frequency-voltage noise properties of a small-sized stack of intrinsic Josephson junctions formed on the surface of a cleaved Bi2Sr2CaCu2Oy (Bi-2212) single crystal, containing a few intrinsic Josephson junctions. A stack with an area of 2×2μm was fabricated by electron-beam lithography and argon-ion-milling. The current–voltage (I–V) characteristics along the c-axis direction of the stack were measured by a three-terminal method. The stack showed (I–V) and dV∕dI-V curves without backbending due to heating effects. Five discrete resistive branches with hysteresis were observed in the low-voltage region of these curves. The measured noise-voltage spectral density SV(f) had a 1∕f dependence on frequency. We estimated the magnitude of the 1∕f noise parameter η from SV(f) in a Bi-2212 stack and found that above the sum-gap voltage in a small-sized stack η was almost the same as that for low-Tc Nb∕Al+AlOx∕Nb high-quality tunnel junctions.
With a thin gold layer, we fabricated mesa-like shunted intrinsic Josephson junction stacks on Bi2Sr2CaCu2O8+x single crystals. Instead of the multibranch structure and large voltage jumps often observed in conventional intrinsic junctions, current–voltage characteristics typical of resistively shunted junctions were obtained. Individual Shapiro steps were clearly visible with irradiation at frequencies from a few to 20 GHz. The experiments demonstrated not only the ac Josephson effects directly but also the possibility of employing intrinsic Josephson junctions in high-frequency applications.
The conventional c-axis intrinsic Josephson junction (IJJ) stack is usually fabricated from a piece of single crystal in such a way that it looks like a small mesa sitting on a big pedestal. In some cases the effects of this pedestal should be taken into account in order to explain the experimental observations. To avoid this problem we have developed a novel technique by which we are able to remove a small sample from the single crystal and place it on a substrate with low microwave loss. This enable us to couple it to other microwave devices such as antenna etc. This small sample, or junction stack, measures a few micrometers by a few micrometers in the a-b plane and a few hundred angstroms along the c-axis and is plated with normal metal on both the top and the bottom. To distinguish the structure from the conventional one, we call it an insular intrinsic Josephson junction stack. We carefully study current-voltage characteristics, microwave responses, frequency mixing properties, and discuss the possible applications.
Two-stacked intrinsic Josephson junctions (IJJs) on a Bi2Sr2CaCu2O8+δ(Bi-2212) whisker with a submicron hole are micromachined by a 3D focused ion beam (FIB) etching method. The junction area, the number of elementary junctions, and the loop area of the SQUIDs are 3, 20, and 0.42 μm2, respectively. The SQUIDs show typical I–V characteristics of IJJs with a critical current IC of 12 μA at 4.2 K. The modulation parameter βL(=2ICL/Φ0) is 6.4, and the inductance L of the SQUID is 1120 pH. That includes the inductances of the elementary junction around a SQUID loop. In a strong magnetic field, the Fraunhofer pattern is obtained and well fitted to the calculated value from the junction size, ΔB=Φ0/tW; t is the interlayer distance, and W is the junction width. In a low magnetic field, approximately 10% of the IC modulation corresponding to the value of βL is observed. Eighty G of the modulation period approximately agrees with the value calculated from the SQUID.