scholarly journals Josephson Effect in MgB2/Pd/Nb Trilayer Josephson Junctions

2021 ◽  
Vol 47 (3) ◽  
pp. 1062-1072
Author(s):  
Anayesu B Malisa
Keyword(s):  
Josephson Junctions ◽  
Josephson Effect ◽  
Molecular Beam ◽  
Bottom Electrode ◽  
Tunnel Junctions ◽  
Rf Sputtering ◽  
Ex Situ ◽  
Shapiro Steps ◽  
Josephson Tunnel ◽  
Junction Plane

This paper reports fabrication techniques and results of MgB2/Pd/Nb trilayer Josephson junctions. The MgB2 bottom electrode was co-evaporated by molecular beam epitaxy (MBE) technique from both magnesium and boron sources at a low substrate temperature ~ 300 °C, while the interlayer and the top niobium electrode (Pd/Nb bilayer) were deposited ex-situ using RF sputtering. The junctions exhibited  and  Josephson effect as well as a modulation of the critical current in a magnetic field applied in a direction normal to the junction plane. Fractional and integer Shapiro steps were observed at voltages corresponding to the frequency of the applied microwave radiation field. The  products of the junctions compare well with the previously reported values. The results suggest that it should be possible to fabricate all-MgB2 and MgB2 as one of the electrodes Superconductor/Normal/Superconductor (SNS), Superconductor/Insulator/Superconductor (SIS) or even Superconductor/Ferromagnet/Superconductor (SFS) tunnel junctions with interesting characteristics and for various applications. Keywords: MgB2; all-MgB2; Josephson Tunnel junctions; trilayer devices; Niobium

Josephson junctions based on amorphous MoGe: prospects for use in superconducting electronics

2022 ◽  
Author(s):  
Ivan P Nevirkovets ◽  
Mikhail A Belogolovskii ◽  
John B Ketterson
Keyword(s):  
Experimental Data ◽  
Surface Morphology ◽  
Temperature Dependence ◽  
Josephson Junctions ◽  
Tunnel Junctions ◽  
Theoretical Calculations ◽  
Superconducting Transition ◽  
High Uniformity ◽  
Josephson Tunnel ◽  
Superconducting Electronics

Abstract We have fabricated and characterized all-MoGe Josephson junctions with a very thin Al/AlOx/(Al) barrier, where the amorphous MoGe films exhibit superconducting transition temperatures up to 7 K. Due to the uniformity of the surface morphology of the MoGe films, the junctions demonstrate high uniformity of their tunneling properties. The experimental data on the temperature dependence of the subgap current agree well with theoretical calculations. The results obtained imply that Josephson tunnel junctions based on amorphous superconductors are promising candidates for use in superconducting electronics, especially in applications requiring multiple stacked junctions or the creation of a nonequilibrium quasiparticle distribution.

Proximity-Effect and Tunneling in YBa2Cu3O7/Metal Layered Structures

1989 ◽  
Vol 169 ◽  
Author(s):  
L. H. Greene ◽  
W. L. Feldmann ◽  
J. B. Barrier ◽  
L. A. Farrow ◽  
P. F. Miceli ◽  
...  
Keyword(s):  
Tunnel Junctions ◽  
Normal Metal ◽  
Ex Situ ◽  
Superconducting Thin Films ◽  
Composite Target ◽  
Shapiro Steps ◽  
Target Composition ◽  
Planar Magnetron ◽  
Metal Bilayers

AbstractSuperconducting thin films of YBa2Cu3O7 are prepared in-situ by on-axis, sputter deposition from a single, composite target. Our planar magnetron target composition of Y:Ba:Cu = 1.08:1.76:4.5 sputtered onto MgO at T~750°C in a 600mTorr Ar-O2 atmosphere yields reproducible superconducting films having Tc(R = 0)>80K and stoichiometry 1:2:3, that are shiny and of near epitaxial, crystalline quality. In order to ensure clean interfaces, YBa2Cu3O7/normal metal bilayers (to form SNS' Josephson junctions) and YBa2Cu3O7/normal metal/insulating barrier trilayers (to form SNIS' proximity tunnel junctions) are grown completely in-situ. (The S' = Pb counter electrode is evaporated ex-situ.) A supercurrent and Shapiro steps are observed in microwave irradiated SNS' (N = Ag) small area (5x10-5cm2) junctions. In SNIS' tunnel junctions, high-quality Pb tunneling is observed.

scholarly journals Phase-dependent noise in Josephson junctions

2018 ◽  
Vol 81 (1) ◽  
pp. 10601
Author(s):  
Forrest Sheldon ◽  
Sebastiano Peotta ◽  
Massimiliano Di Ventra
Keyword(s):  
Stationary Phase ◽  
Tunnel Junction ◽  
Josephson Junctions ◽  
Thermal Noise ◽  
Tunnel Junctions ◽  
Microscopic Theory ◽  
Phase Dependence ◽  
Dynamic Noise ◽  
Josephson Tunnel ◽  
Superconducting Current

In addition to the usual superconducting current, Josephson junctions (JJs) support a phase-dependent conductance related to the retardation effect of tunneling quasi-particles. This introduces a dissipative current with a memory-resistive (memristive) character that should also affect the current noise. By means of the microscopic theory of tunnel junctions we compute the complete current autocorrelation function of a Josephson tunnel junction and show that this memristive component gives rise to both a previously noted phase-dependent thermal noise, and an undescribed non-stationary, phase-dependent dynamic noise. As experiments are approaching ranges in which these effects may be observed, we examine the form and magnitude of these processes. Their phase dependence can be realized experimentally as a hysteresis effect and may be used to probe defects present in JJ based qubits and in other superconducting electronics applications.

Oxide Quantum Structures for Future Electro-Photonics

1997 ◽  
Vol 474 ◽  
Author(s):  
M. Kawasaki ◽  
A. Ohtomo ◽  
R. Tsuchiya ◽  
J. Nishino ◽  
H. Koinuma
Keyword(s):  
Josephson Effect ◽  
Room Temperature ◽  
Molecular Beam ◽  
Tunnel Junctions ◽  
Substrate Surface ◽  
Growth Dynamics ◽  
Quantum Structures ◽  
Zno Films ◽  
Wire Arrays ◽  
Self Organized

ABSTRACTWe show our recent development on the epitaxial growth of oxide thin films by laser molecular beam epitaxy directed towards a possible new field of electro-photonics based on metal-oxide quantum structures. Examples of quantum structures include superlattices and tunnel junctions (2-dimensional), superconducting quantum wire arrays (1-dimensional), and quantum dots for photonic application (O-dimensional). For fabricating such structures, it is vitally important to prepare the substrate surface and to understand the growth dynamics. Such electro-phptonic functions as Josephson effect in high Tc tunnel junctions and excitonic UV-laser operation at room temperature in self-organized hexagonal nanocrystal ZnO films are presented.

Effects of the radio-frequency sputtering power of an MgO tunneling barrier on the tunneling magneto-resistance ratio for Co2Fe6B2/MgO-based perpendicular-magnetic tunnel junctions

2016 ◽  
Vol 4 (1) ◽  
pp. 135-141 ◽  
Author(s):  
Du-Yeong Lee ◽  
Hyung-Tak Seo ◽  
Jea-Gun Park
Keyword(s):  
Radio Frequency ◽  
Tunnel Junctions ◽  
Rf Sputtering ◽  
Resistance Ratio ◽  
Spin Valves ◽  
Ex Situ ◽  
Tunneling Barrier ◽  
Radio Frequency Sputtering ◽  
Sputtering Power ◽  
Magneto Resistance

For Co2Fe6B2–MgO based p-MTJ spin valves with [Co/Pt]n–SyAF layers ex situ annealed at 350 °C and 30 kOe for 30 min, the tunneling magneto-resistance (TMR) ratio strongly depended on the radio-frequency (RF) sputtering power in a 0.65–1.15 nm thick MgO tunneling barrier, achieving a TMR ratio of 168% at 300 W.

An in situ and ex situ TEM study of the formation of thin cobalt silicide films by molecular beam epitaxy on the silicon (100) surface

1988 ◽  
Vol 46 ◽  
pp. 884-885
Author(s):  
D. Loretto ◽  
J. M. Gibson ◽  
S. M. Yalisove ◽  
R. T. Tung
Keyword(s):  
Molecular Beam Epitaxy ◽  
Molecular Beam ◽  
Defect Density ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Ex Situ ◽  
Metal Base ◽  
In Situ Experiments ◽  
Potential Applications

The cobalt disilicide/silicon system has potential applications as a metal-base and as a permeable-base transistor. Although thin, low defect density, films of CoSi2 on Si(111) have been successfully grown, there are reasons to believe that Si(100)/CoSi2 may be better suited to the transmission of electrons at the silicon/silicide interface than Si(111)/CoSi2. A TEM study of the formation of CoSi2 on Si(100) is therefore being conducted. We have previously reported TEM observations on Si(111)/CoSi2 grown both in situ, in an ultra high vacuum (UHV) TEM and ex situ, in a conventional Molecular Beam Epitaxy system.The procedures used for the MBE growth have been described elsewhere. In situ experiments were performed in a JEOL 200CX electron microscope, extensively modified to give a vacuum of better than 10-9 T in the specimen region and the capacity to do in situ sample heating and deposition. Cobalt was deposited onto clean Si(100) samples by thermal evaporation from cobalt-coated Ta filaments.

Interfacial properties of GaSb/InAs superlattices

1993 ◽  
Vol 51 ◽  
pp. 826-827
Author(s):  
M. E. Twigg ◽  
B. R. Bennett ◽  
J. R. Waterman ◽  
J. L. Davis ◽  
B. V. Shanabrook ◽  
...  
Keyword(s):  
Gaas Substrate ◽  
Molecular Beam ◽  
Infrared Detector ◽  
Interfacial Properties ◽  
Ex Situ ◽  
X Ray Diffraction ◽  
Absorption Coefficients ◽  
X Ray ◽  
Short Period ◽  
High Optical Absorption

Recently, the GaSb/InAs superlattice system has received renewed attention. The interest stems from a model demonstrating that short period Ga1-xInxSb/InAs superlattices will have both a band gap less than 100 meV and high optical absorption coefficients, principal requirements for infrared detector applications. Because this superlattice system contains two species of cations and anions, it is possible to prepare either InSb-like or GaAs-like interfaces. As such, the system presents a unique opportunity to examine interfacial properties.We used molecular beam epitaxy (MBE) to prepare an extensive set of GaSb/InAs superlattices grown on an GaSb buffer, which, in turn had been grown on a (100) GaAs substrate. Through appropriate shutter sequences, the interfaces were directed to assume either an InSb-like or GaAs-like character. These superlattices were then studied with a variety of ex-situ probes such as x-ray diffraction and Raman spectroscopy. These probes confirmed that, indeed, predominantly InSb-like and GaAs-like interfaces had been achieved.

Titania Based Nano-ionic Memristive Crossbar Arrays: Fabrication and Resistive Switching Characteristics

2019 ◽  
Vol 9 (4) ◽  
pp. 486-493 ◽  
Author(s):  
S. Sahoo ◽  
P. Manoravi ◽  
S.R.S. Prabaharan
Keyword(s):  
Resistive Switching ◽  
Bottom Electrode ◽  
Rf Sputtering ◽  
Hysteresis Curve ◽  
Bipolar Switching ◽  
Post Annealing ◽  
Endurance Tests ◽  
Bilayer Device ◽  
Switching Characteristics ◽  
Pinched Hysteresis

Introduction: Intrinsic resistive switching properties of Pt/TiO2-x/TiO2/Pt crossbar memory array has been examined using the crossbar (4×4) arrays fabricated by using DC/RF sputtering under specific conditions at room temperature. Materials and Methods: The growth of filament is envisaged from bottom electrode (BE) towards the top electrode (TE) by forming conducting nano-filaments across TiO2/TiO2-x bilayer stack. Non-linear pinched hysteresis curve (a signature of memristor) is evident from I-V plot measured using Pt/TiO2-x /TiO2/Pt bilayer device (a single cell amongst the 4×4 array is used). It is found that the observed I-V profile shows two distinguishable regions of switching symmetrically in both SET and RESET cycle. Distinguishable potential profiles are evident from I-V curve; in which region-1 relates to the electroformation prior to switching and region-2 shows the switching to ON state (LRS). It is observed that upon reversing the polarity, bipolar switching (set and reset) is evident from the facile symmetric pinched hysteresis profile. Obtaining such a facile switching is attributed to the desired composition of Titania layers i.e. the rutile TiO2 (stoichiometric) as the first layer obtained via controlled post annealing (650oC/1h) process onto which TiO2-x (anatase) is formed (350oC/1h). Results: These controlled processes adapted during the fabrication step help manipulate the desired potential barrier between metal (Pt) and TiO2 interface. Interestingly, this controlled process variation is found to be crucial for measuring the switching characteristics expected in Titania based memristor. In order to ensure the formation of rutile and anatase phases, XPS, XRD and HRSEM analyses have been carried out. Conclusion: Finally, the reliability of bilayer memristive structure is investigated by monitoring the retention (104 s) and endurance tests which ensured the reproducibility over 10,000 cycles.

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