scholarly journals Gate Control of Superconductivity in Mesoscopic All-Metallic Devices

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1243
Author(s):  
Claudio Puglia ◽  
Giorgio De Simoni ◽  
Francesco Giazotto
Keyword(s):  
Probability Distributions ◽  
Superconducting Properties ◽  
Microscopic Mechanism ◽  
Technological Potential ◽  
Half Wave ◽  
Thermal Origin ◽  
Gate Control ◽  
Titanium Wire ◽  
Field Emission Of Electrons ◽  
Gating Effect

The possibility to tune, through the application of a control gate voltage, the superconducting properties of mesoscopic devices based on Bardeen–Cooper–Schrieffer metals was recently demonstrated. Despite the extensive experimental evidence obtained on different materials and geometries, a description of the microscopic mechanism at the basis of such an unconventional effect has not been provided yet. This work discusses the technological potential of gate control of superconductivity in metallic superconductors and revises the experimental results, which provide information regarding a possible thermal origin of the effect: first, we review experiments performed on high-critical-temperature elemental superconductors (niobium and vanadium) and show how devices based on these materials can be exploited to realize basic electronic tools, such as a half-wave rectifier. Second, we discuss the origin of the gating effect by showing gate-driven suppression of the supercurrent in a suspended titanium wire and by providing a comparison between thermal and electric switching current probability distributions. Furthermore, we discuss the cold field-emission of electrons from the gate employing finite element simulations and compare the results with experimental data. In our view, the presented data provide a strong indication regarding the unlikelihood of the thermal origin of the gating effect.

Properties of some superconductors

1940 ◽  
Vol 36 (1) ◽  
pp. 84-93 ◽  
Author(s):  
D. Shoenberg
Keyword(s):  
Critical Field ◽  
Magnetic Induction ◽  
Pure Aluminium ◽  
Superconducting Properties ◽  
Induction Method ◽  
A Value ◽  
Titanium Wire ◽  
Zero Resistance ◽  
Titanium Specimen

The critical-field curves of pure aluminium, gallium, thorium and zinc were measured by a magnetic induction method. An unusually marked supercooling effect was found in aluminium and to a much smaller extent also in gallium; some experiments on this effect are discussed. The first three of these metals were found to have “ideally pure” superconducting properties, and thorium, although belonging to the “hard” group of superconductors, had a value of dHc/dT of only 190 gauss/degree K. Only a very minute fraction of the volume of a titanium specimen was found to become superconducting at temperatures down to 1° K., although Meissner had found a titanium wire to have zero resistance below 1·8° K.; an explanation of this discrepancy is put forward. Molybdenum and uranium did not become superconducting down to 0·3 and 0·98° K. respectively, though, in the case of one uranium sample, a small fraction of the volume showed superconducting effects as in titanium.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

Characterization of Y-Ba-Cu-O films grown on silicon substrates by sequential evaporation

1988 ◽  
Vol 46 ◽  
pp. 866-867
Author(s):  
E. L. Hall ◽  
A. Mogro-Campero ◽  
L. G. Turner ◽  
N. Lewis
Keyword(s):  
Thin Film ◽  
Thin Film Deposition ◽  
Superconducting Films ◽  
Electron Beam Evaporation ◽  
Film Deposition ◽  
Silicon Substrates ◽  
Superconducting Properties ◽  
Sequential Electron ◽  
Thin Superconducting Films

There is great interest in the growth of thin superconducting films of YBa2Cu3Ox on silicon, since this is a necessary first step in the use of this superconductor in a variety of possible electronic applications including interconnects and hybrid semiconductor/superconductor devices. However, initial experiments in this area showed that drastic interdiffusion of Si into the superconductor occurred during annealing if the Y-Ba-Cu-O was deposited direcdy on Si or SiO2, and this interdiffusion destroyed the superconducting properties. This paper describes the results of the use of a zirconia buffer layer as a diffusion barrier in the growth of thin YBa2Cu3Ox films on Si. A more complete description of the growth and characterization of these films will be published elsewhere.Thin film deposition was carried out by sequential electron beam evaporation in vacuum onto clean or oxidized single crystal Si wafers. The first layer evaporated was 0.4 μm of zirconia.

Studies of the scanning ion beam sputter-cleaned MgO crystal surface by scanning reflection electron microscopy

1987 ◽  
Vol 45 ◽  
pp. 144-145
Author(s):  
H.-J. Ou ◽  
J. M. Cowley ◽  
A. A. Higgs
Keyword(s):  
Crystal Surface ◽  
Ion Beam ◽  
Carbon Film ◽  
Surface Region ◽  
Bulk Sample ◽  
Chamber Pressure ◽  
Specimen Preparation ◽  
Detailed Surface ◽  
Gate Control ◽  
Reflection Electron Microscopy

A scanning ion gun system has been installed on the specimen preparation chamber (pressure ∼5xl0-8 torr) of the VG-HB5 STEM microscope. By using the specimen current imaging technique, it is possible to use an ion beam to sputter-clean the preferred surface region on a bulk sample. As shown in figure 1, the X-Y raster-gate control of the scanning unit for the Krato Mini-Beam I is used to minimize the beam raster area down to a 800μm x800μm square region. With beam energy of 2.5KeV, the MgO cleavage surface has been ion sputter-cleaned for less than 1 minute. The carbon film or other contaminant, introduced during the cleavage process in air, is mostly removed from the MgO crystal surfaces.The immediate SREM inspection of this as-cleaned MgO surface, within the adjacent STEM microscope, has revealed the detailed surface structures of atomic steps, which were difficult to observe on the as-cleaved MgO surfaces in the previous studies.

TEM investigations of surface residual stress relaxation in A12O3 and Al2O3-SiC nanocomposite

1994 ◽  
Vol 52 ◽  
pp. 628-629
Author(s):  
J. Fang ◽  
H. M. Chan ◽  
M. P. Harmer
Keyword(s):  
Residual Stress ◽  
Single Phase ◽  
Stress Relief ◽  
Stress Recovery ◽  
Surface Residual Stress ◽  
Microscopic Mechanism ◽  
Sic Particles ◽  
Annealing Procedure ◽  
The Difference ◽  
Nano Size

It was Niihara et al. who first discovered that the fracture strength of Al2O3 can be increased by incorporating as little as 5 vol.% of nano-size SiC particles (>1000 MPa), and that the strength would be improved further by a simple annealing procedure (>1500 MPa). This discovery has stimulated intense interest on Al2O3/SiC nanocomposites. Recent indentation studies by Fang et al. have shown that residual stress relief was more difficult in the nanocomposite than in pure Al2O3. In the present work, TEM was employed to investigate the microscopic mechanism(s) for the difference in the residual stress recovery in these two materials.Bulk samples of hot-pressed single phase Al2O3, and Al2O3 containing 5 vol.% 0.15 μm SiC particles were simultaneously polished with 15 μm diamond compound. Each sample was cut into two pieces, one of which was subsequently annealed at 1300° for 2 hours in flowing argon. Disks of 3 mm in diameter were cut from bulk samples.

Processing and characterization of YBa2Cu3O7−x/Ag composites

1990 ◽  
Vol 48 (4) ◽  
pp. 46-47
Author(s):  
Jafar Javadpour ◽  
Bradley L. Thiel ◽  
Sarikaya Mehmet ◽  
Ilhan A. Aksay
Keyword(s):  
Composite System ◽  
Precursor Solution ◽  
Microstructural Development ◽  
Superconducting Properties ◽  
Practical Applications ◽  
Nitrate Precursor ◽  
Cold Pressed ◽  
Tape Cast ◽  
Composite Samples

Practical applications of bulk YBa2Cu3O7−x materials have been limited because of their inadequate critical current density (jc) and poor mechanical properties. Several recent reports have indicated that the addition of Ag to the YBa2Cu3O7−x system is beneficial in improving both mechanical and superconducting properties. However, detailed studies concerning the effect of Ag on the microstructural development of the cermet system have been lacking. Here, we present some observations on the microstructural evolution in the YBa2Cu3O7−x/Ag composite system.The composite samples were prepared by mixing various amounts (2.5 - 50 wt%) AgNO3 in the YBa2Cu3O7−x nitrate precursor solution. These solutions were then spray dried and the resulting powders were either cold pressed or tape cast. The microstructures of the sintered samples were analyzed using SEM (Philips 515) and an analytical TEM (Philips 430T).The SEM micrographs of the compacts with 2.5 and 50 wt% Ag addition sintered at 915°C (below the melting point of Ag) for 1 h in air are displayed in Figs. 1 and 2, respectively.

SUPERCONDUCTING PROPERTIES OF IRIDIUM THIN FILMS

1978 ◽  
Vol 39 (C6) ◽  
pp. C6-608-C6-609
Author(s):  
L. B. Holdeman ◽  
R. J. Soulen ◽  
Jr ◽  
T. F. Finnegan ◽  
P. N. Peters
Keyword(s):  
Thin Films ◽  
Superconducting Properties

MAGNETIC AND SUPERCONDUCTING PROPERTIES OF SUBSTITUTED YBa2 (Cu1-xMx)3 O7 COMPOUNDS (M = 3d METAL)

1988 ◽  
Vol 49 (C8) ◽  
pp. C8-2201-C8-2202
Author(s):  
Ying-Chang Yang ◽  
Yuan-Bo Zha ◽  
Wei-Chun Yuan ◽  
Jian Lan ◽  
Zun-Xiao Liu ◽  
...  
Keyword(s):  
Superconducting Properties

Resilienz, Ressourcen, Bewältigung

2017 ◽  
Vol 36 (05) ◽  
pp. 355-360
Author(s):  
E. Geissner
Keyword(s):  
Pain Management ◽  
Behavioral Medicine ◽  
Chronischer Schmerz ◽  
Gate Control

ZusammenfassungChronischer Schmerz ist in der Psychologie seit rund 50 Jahren Gegenstand vertiefter wissenschaftlicher Beschäftigung: Grundlagenwissenschaftlich gilt als Startpunkt die Arbeit zur Gate-Control-Theorie im Jahr 1965 (3), anwendungsorientiert die Monografie Pain and Behavioral Medicine, 1983 (6). Auch wenn Schmerz durch psychologische Maßnahmen nicht vollends verschwindet, so sind doch wirksame Möglichkeiten bekannt, diesen substanziell in den Hintergrund zu rücken, das Leiden zu reduzieren, einen gut adaptierten Lebensvollzug wiederherzustellen. Der Resilienz-(R-)begriff entstammt der Entwicklungspsychologie und liefert für die vorliegende Thematik wertvolle Beiträge. Heutige R-Forscher betonen die Förderung von R. Dies geschieht durch wiederholte Auseinandersetzung mit Herausforderungen – hier Schmerz –, im Rahmen derer neue Fähigkeiten erworben und Belastungen gemeistert werden. Ein Assimilationsmodus (AS) ist von einem Akkommodationsmodus (AK) zu unterscheiden. AS beinhaltet die Kompensation eines verlorenen Standards durch Übungen, Techniken, Training, systematische Praxis, während AK gedanklich-emotionales Umbewerten, Akzeptanz und Relativieren früherer Standards zum Ziel hat. Gut kompatibel mit R ist der Ressourcenansatz der klinischen Psychologie. Hier werden Aktiva, Positiva und Stärken der Person fokussiert und der Defizitansatz der herkömmlichen Psychotherapie ergänzt. Mit dem Ressourcenansatz einher geht Psychotherapie bei Schmerz, wohingegen Bewältigung (Coping) eher assimilativ auf Training und Pain-Management orientiert ist. Schmerzbewältigungstrainings (ambulant, stationär) mit einer Reihe von verhaltens-, kognitiven, emotions- und körper-/bewegungsorientierten Verfahren werden abschließend erläutert.

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