| 1. |
- Ciancio, Regina, 1978, et al.
(author)
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Electron backscattering diffraction and X-ray diffraction studies of interface relationships in Sr3Ru2O7/Sr2RuO4 eutectic crystals
- 2011
-
In: Micron. - : Elsevier BV. - 0968-4328. ; 42:4, s. 324-329
-
Journal article (peer-reviewed)abstract
- Sr3Ru2O7/Sr2RuO4 eutectic system is investigated by electron backscattering diffraction (EBSD) and X-ray diffraction (XRD). The eutectic growth enables the solidification of the two phases in an ordered lamellar pattern extending along the growth direction, namely the b-axis direction. The eutectic material thus provides in the a-c plane two distinct interfaces having different microstructures with respect to the growth direction. Our analysis shows that, across the inplane c-axis direction (characterized by a poor lattice matching), the b-axis orientation is not constant at the individual interfaces, showing an orientation spread of about 5 degrees. However, across the in-plane a-axis direction (characterized by a good lattice matching), the b-axis orientation does not change within a few tenths of degree (about 0.25 degrees). Such information at nanoscale is also verified on a macroscopic level by standard XRD investigation.
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| 2. |
- Ngaloy, Roselle, 1994, et al.
(author)
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Strong In-Plane Magnetization and Spin Polarization in (Co 0.15 Fe 0.85 ) 5 GeTe 2 /Graphene van der Waals Heterostructure Spin-Valve at Room Temperature
- 2023
-
In: ACS Nano. - 1936-086X .- 1936-0851. ; In Press
-
Journal article (peer-reviewed)abstract
- Van der Waals (vdW) magnets are promising, because of their tunable magnetic properties with doping or alloy composition, where the strength of magnetic interactions, their symmetry, and magnetic anisotropy can be tuned according to the desired application. However, so far, most of the vdW magnet-based spintronic devices have been limited to cryogenic temperatures with magnetic anisotropies favoring out-of-plane or canted orientation of the magnetization. Here, we report beyond room-temperature lateral spin-valve devices with strong in-plane magnetization and spin polarization of the vdW ferromagnet (Co0.15Fe0.85)5GeTe2 (CFGT) in heterostructures with graphene. Density functional theory (DFT) calculations show that the magnitude of the anisotropy depends on the Co concentration and is caused by the substitution of Co in the outermost Fe layer. Magnetization measurements reveal the above room-temperature ferromagnetism in CFGT and clear remanence at room temperature. Heterostructures consisting of CFGT nanolayers and graphene were used to experimentally realize basic building blocks for spin valve devices, such as efficient spin injection and detection. Further analysis of spin transport and Hanle spin precession measurements reveals a strong in-plane magnetization with negative spin polarization at the interface with graphene, which is supported by the calculated spin-polarized density of states of CFGT. The in-plane magnetization of CFGT at room temperature proves its usefulness in graphene lateral spin-valve devices, thus revealing its potential application in spintronic technologies.
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| 3. |
- Zhao, Bing, 1990, et al.
(author)
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A Room-Temperature Spin-Valve with van der Waals Ferromagnet Fe 5 GeTe 2 /Graphene Heterostructure
- 2023
-
In: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 35:16
-
Journal article (peer-reviewed)abstract
- The discovery of van der Waals (vdW) magnets opened a new paradigm for condensed matter physics and spintronic technologies. However, the operations of active spintronic devices with vdW ferromagnets are limited to cryogenic temperatures, inhibiting their broader practical applications. Here, the robust room-temperature operation of lateral spin-valve devices using the vdW itinerant ferromagnet Fe5GeTe2 in heterostructures with graphene is demonstrated. The room-temperature spintronic properties of Fe5GeTe2 are measured at the interface with graphene with a negative spin polarization. Lateral spin-valve and spin-precession measurements provide unique insights by probing the Fe5GeTe2/graphene interface spintronic properties via spin-dynamics measurements, revealing multidirectional spin polarization. Density functional theory calculations in conjunction with Monte Carlo simulations reveal significantly canted Fe magnetic moments in Fe5GeTe2 along with the presence of negative spin polarization at the Fe5GeTe2/graphene interface. These findings open opportunities for vdW interface design and applications of vdW-magnet-based spintronic devices at ambient temperatures.
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| 4. |
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| 5. |
- Öisjöen, Fredrik, 1982, et al.
(author)
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High-Tc SQUID gradiometer system for immunoassays
- 2008
-
In: Superconductor Science and Technology. - : IOP Publishing. - 0953-2048 .- 1361-6668. ; 21:3, s. Art. Nr. 034004-
-
Journal article (peer-reviewed)abstract
- A high-Tc dc SQUID (superconducting quantum interference device) gradiometer was developed for magnetic immunoassays where magnetic nanoparticles are used as markers todetect biological reactions. The gradiometer was fabricated on a 5 × 10 mm2 SrTiO3 bicrystal substrate and has a gradiometer resolution of 2.1 pT cm−1 Hz−1/2. A magnetic signal was detected from a sample of 1 μl of Fe3O4 nanoparticles in a 40 mg ml−1 solution kept in amicrocavity fabricated on Si wafers with Si3N4 membranes using MEMS (micro-electro-mechanical-systems) technology. It was found that volumes as small as 0.3 nl in principle would be detectable with our present device. This corresponds to a total number of particles of 2.2 × 107. The estimated average dipole moment per particle is 4.8 × 10−22 Am2.We are aiming at reading out immunoassays by detecting the Brownian relaxation of magnetic nanoparticles, and we also intend to integrate MEMS technology into our system.
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| 6. |
- Ahrentorp, Fredrik, et al.
(author)
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Sensitive magnetic biodetection using magnetic multi-core nanoparticles and RCA coils
- 2017
-
In: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 427, s. 14-18
-
Journal article (peer-reviewed)abstract
- We use functionalized iron oxide magnetic multi-core particles of 100 nm in size (hydrodynamic particle diameter) and AC susceptometry (ACS) methods to measure the binding reactions between the magnetic nanoparticles (MNPs) and bio-analyte products produced from DNA segments using the rolling circle amplification (RCA) method. We use sensitive induction detection techniques in order to measure the ACS response. The DNA is amplified via RCA to generate RCA coils with a specific size that is dependent on the amplification time. After about 75 min of amplification we obtain an average RCA coil diameter of about 1 mu m. We determine a theoretical limit of detection (LOD) in the range of 11 attomole (corresponding to an analyte concentration of 55 fM for a sample volume of 200 mu L) from the ACS dynamic response after the MNPs have bound to the RCA coils and the measured ACS readout noise. We also discuss further possible improvements of the LOD.
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| 7. |
- Andersson, Eric, 1992, et al.
(author)
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Nondestructive cleaning of the LaAlO3/SrTiO3 surface with ultraviolet light and ozone
- 2016
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In: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics. - : American Vacuum Society. - 2166-2746 .- 2166-2754. ; 34:4
-
Journal article (peer-reviewed)abstract
- The effect of ultraviolet light produced ozone and irradiation (UV/ozone) cleaning on the surface properties and interface electrical properties of 4 unit cell (uc) LaAlO3/SrTiO3 samples is examined. A standard photolithography process is used to contaminate the samples which are then cleaned in UV/ozone. Atomic force microscopy measurements show that the photoresist contaminated samples can be cleaned efficiently using this method. The surface roughness of the cleaned samples is comparable to that of the as-grown samples. Furthermore, electrical transport measurements show that the mobility decreases and the sheet carrier density increases for the contaminated samples, which also display indications of an onset to the Kondo effect. By removing the contaminants with UV/ozone cleaning, the mobility and sheet carrier density can be partially restored toward the as-grown values. The mobility is increased by about two times from approximate to 1000 cm(2) V-1 s(-1) for the contaminated samples to approximate to 2000 cm(2) V-1 s(-1) for the ozone cleaned ones. (C) 2016 American Vacuum Society.
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| 8. |
- Arpaia, Riccardo, 1985, et al.
(author)
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Engineering underdoped CuO2 nanoribbons in nm-thick a -axis YBa2Cu3 O7-δ films
- 2024
-
In: Physical Review Materials. - 2475-9953. ; 8:4
-
Journal article (peer-reviewed)abstract
- In underdoped cuprate high-Tc superconductors, various local orders and symmetry-breaking states, in addition to superconductivity, reside in the CuO2 planes. The confinement of the CuO2 planes can therefore play a fundamental role in modifying the hierarchy between the various orders and their intertwining with superconductivity. Here we present the growth of a-axis oriented YBa2Cu3O7-δ films, spanning the whole underdoped side of the phase diagram. In these samples, the CuO2 planes are confined by the film thickness, effectively forming unit-cell-thick nanoribbons. The unidirectional confinement at the nanoscale enhances the in-plane anisotropy of the films. By x-ray diffraction and resistance vs temperature measurements, we have discovered the suppression of the orthorhombic-to-tetragonal transition at low dopings, and a very high anisotropy of the normal state resistance in the b-c plane, the latter being connected to a weak coupling between adjacent CuO2 nanoribbons. These findings show that the samples we have grown represent a novel system, different from the bulk, where future experiments can possibly shed light on the rich and mysterious physics occurring within the CuO2 planes.
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| 9. |
- Arpaia, Riccardo, 1985, et al.
(author)
-
Engineering underdoped CuO2 nanoribbons in nm-thick a -axis YBa2Cu3 O7-δ films
- 2024
-
In: Physical Review Materials. - : American Physical Society. - 2475-9953. ; 8:4
-
Journal article (peer-reviewed)abstract
- In underdoped cuprate high-Tc superconductors, various local orders and symmetry-breaking states, in addition to superconductivity, reside in the CuO2 planes. The confinement of the CuO2 planes can therefore play a fundamental role in modifying the hierarchy between the various orders and their intertwining with superconductivity. Here we present the growth of a-axis oriented YBa2Cu3O7-δ films, spanning the whole underdoped side of the phase diagram. In these samples, the CuO2 planes are confined by the film thickness, effectively forming unit-cell-thick nanoribbons. The unidirectional confinement at the nanoscale enhances the in-plane anisotropy of the films. By x-ray diffraction and resistance vs temperature measurements, we have discovered the suppression of the orthorhombic-to-tetragonal transition at low dopings, and a very high anisotropy of the normal state resistance in the b-c plane, the latter being connected to a weak coupling between adjacent CuO2 nanoribbons. These findings show that the samples we have grown represent a novel system, different from the bulk, where future experiments can possibly shed light on the rich and mysterious physics occurring within the CuO2 planes.
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| 10. |
- Arpaia, Riccardo, 1985, et al.
(author)
-
Untwinned YBa2Cu3O7-delta thin films on MgO substrates: A platform to study strain effects on the local orders in cuprates
- 2019
-
In: Physical Review Materials. - 2475-9953. ; 3:11
-
Journal article (peer-reviewed)abstract
- We have grown untwinned YBa2Cu3O7-delta (YBCO) films on (110) MgO substrates that were preannealed at high temperature in oxygen atmosphere. The annealing results in surface reconstruction with shallow facets, which induce the suppression of the YBCO twinning domains, and the preferential alignment of the CuO chains along one of the in-plane directions of the substrate. Because of the large mismatch between the in-plane lattice parameters of film and substrate, the strain induced by the MgO into the YBCO layer is strong and very peculiar. The YBCO film is compressed, with respect to the bulk, and presents a unidirectional buckling of the atomic planes, along the chains' direction, due to a deformation of the copper-oxygen octahedra. The YBCO films, which can be grown with thicknesses down to few unit cells and oxygen doping levels spanning most of the superconducting dome, are patterned into nanowires with dimensions down to 50 nm. The anisotropies due to the untwinning state are preserved in these structures; moreover, additional anisotropies appear in ultrathin structures where strain effects become more pronounced. Such untwinned and compressively strained films can therefore be used as a platform to study the interplay between strain and the various local orders in the normal state of YBCO.
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| 11. |
- Aurino, Pier Paolo, 1985, et al.
(author)
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Nano-patterning of the electron gas at the LaAlO3/SrTiO3 interface using low-energy ion beam irradiation
- 2013
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 102:20, s. 201610-
-
Journal article (peer-reviewed)abstract
- The quasi-two dimensional electron gas formed at the interface between LaAlO3 (LAO) and SrTiO3 (STO) shows fascinating properties, such as two-dimensional superconductivity, giant electric field effect, and the possible co-existence of ferromagnetic and superconducting phases. In this work, we demonstrate that the conducting LAO/STO interface can be made insulating after short irradiation by a beam of low energy Ar+ ions. The irradiation process does neither result in physical removal of the LAO film nor produces oxygen vacancies in the STO layer. Using electron beam lithography and low ion beam energy irradiation, we fabricated conducting nano-structures in the LAO/STO interface with dimensions down to 50 nm. Such a reliable and robust method of nano-patterning may be a prerequisite for future electronic applications of the LAO/STO interface.
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| 12. |
- Aurino, Pier Paolo, 1985, et al.
(author)
-
Retention of Electronic Conductivity in LaAlO3/SrTiO3 Nanostructures Using a SrCuO2 Capping Layer
- 2016
-
In: Physical Review Applied. - : American Physical Society. - 2331-7019. ; 6:2
-
Journal article (peer-reviewed)abstract
- The interface between two wide band-gap insulators, LaAlO3 and SrTiO3 (LAO/STO) offers a unique playground to study the interplay and competitions between different ordering phenomena in a strongly correlated two- dimensional electron gas. Recent studies of the LAO/STO interface reveal the inhomogeneous nature of the 2DEG that strongly influences electrical-transport properties. Nanowires needed in future applications may be adversely affected, and our aim is, thus, to produce a more homogeneous electron gas. In this work, we demonstrate that nanostructures fabricated in the quasi-2DEG at the LaAlO3/SrTiO3 interface, capped with a SrCuO2 layer, retain their electrical resistivity and mobility independent of the structure size, ranging from 100 nm to 30 mu m. This is in contrast to noncapped LAO/STO structures, where the room-temperature electrical resistivity significantly increases when the structure size becomes smaller than 1 mu m. High-resolution intermodulation electrostatic force microscopy reveals an inhomogeneous surface potential with "puddles" of a characteristic size of 130 nm in the noncapped samples and a more uniform surface potential with a larger characteristic size of the puddles in the capped samples. In addition, capped structures show superconductivity below 200 mK and nonlinear currentvoltage characteristics with a clear critical current observed up to 700 mK. Our findings shed light on the complicated nature of the 2DEG at the LAO/STO interface and may also be used for the design of electronic devices.
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| 13. |
- Aurino, Pier Paolo, 1985, et al.
(author)
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Reversible metal-insulator transition of Ar-irradiated LaAlO3/SrTiO3 interfaces
- 2015
-
In: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 92:15
-
Journal article (peer-reviewed)abstract
- The conducting state of a quasi-two-dimensional electron gas (q2DEG), formed at the heterointerface between the two wide-bandgap insulators LaAlO3 (LAO) and SrTiO3, can be made completely insulating by low-energy, 150-eV, Ar+ irradiation. The metallic behavior of the interface can be recovered by high-temperature oxygen annealing. The electrical transport properties of the recovered q2DEG are exactly the same as before the irradiation. Microstructural investigations confirm that the transition is not due to physical etching or crystal lattice distortion of the LAO film below its critical thickness. They also reveal a correlation between electrical state, LAO film surface amorphization, and argon ion implantation. The experimental results are in agreement with density functional theory calculations of Ar implantation and migration in the LAO film. This suggests that the metal-insulator transition may be caused by charge trapping in the defect amorphous layer created during the ion irradiation.
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| 14. |
- Barthelemy, A., et al.
(author)
-
Quasi-two-dimensional electron gas at the oxide interfaces for topological quantum physics
- 2021
-
In: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 133:1
-
Journal article (peer-reviewed)abstract
- The development of “fault-tolerant” quantum computers, unaffected by noise and decoherence, is one of the fundamental challenges in quantum technology. One of the approaches currently followed is the realization of “topologically protected” qubits which make use of quantum systems characterized by a degenerate ground state of composite particles, known as “non-Abelian anyons”, able to encode and manipulate quantum information in a non-local manner. In this paper, we discuss the potential of quasi-two-dimensional electron gas (q2DEG) at the interface between band insulating oxides, like LaAlO3 and SrTiO3, as an innovative technological platform for the realization of topological quantum systems. Being characterized by a unique combination of unconventional spin-orbit coupling, magnetism, and 2D-superconductivity, these systems naturally possess most of the fundamental characteristics needed for the realization of a topological superconductor. These properties can be widely tuned by electric field effect acting on the orbital splitting and occupation of the non-degenerate 3dxy and 3dxz,yz bands. The topological state in oxide q2DEGs quasi-one-dimensional nanochannels could be therefore suitably controlled, leading to conceptual new methods for the realization of a topological quantum electronics based on the tuning of the orbital degrees of freedom.
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| 15. |
- Bevilacqua, Stella, 1981, et al.
(author)
-
Fast room temperature THz microbolometers
- 2012
-
In: 23rd International Symposium on Space Terahertz Technology.
-
Conference paper (peer-reviewed)abstract
- We will present experimental and theoretical investigation of room temperature high speed THz detectors based on thin YBa2Cu3O7 films. These films have TCR of 0.35%/K, and can sustain large bias current densities. With a resistivity of 100-200 µOhm×cm for a film thickness of 50nm, it is very straightforward to impedance match such bolometers with planar antennas. The responsivity is a function of the bolometer planar dimensions and the films thickness. The currently achieved responsivity is 30 V/W and Johnson noise limited NEP is 70pW/Hz^0.5. The bolometer bandwidth is limited by the antenna bandwidth and spans from microwaves to over a few THz. Experimenatl investigation is done from 100GHz to 2.5THz. The measured response time is 2ns. We will also present results of the bolometer performance as their dimensions reduce to sub-µm.
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| 16. |
- Blomgren, Jakob, et al.
(author)
-
Development of a sensitive induction-based magnetic nanoparticle biodetection method
- 2018
-
In: Nanomaterials. - : MDPI AG. - 2079-4991. ; 8:11
-
Journal article (peer-reviewed)abstract
- We developed a novel biodetection method for influenza virus based on AC magnetic susceptibility measurement techniques (the DynoMag induction technique) together with functionalized multi-core magnetic nanoparticles. The sample consisting of an incubated mixture of magnetic nanoparticles and rolling circle amplified DNA coils is injected into a tube by a peristaltic pump. The sample is moved as a plug to the two well-balanced detection coils and the dynamic magnetic moment in each position is read over a range of excitation frequencies. The time for making a complete frequency sweep over the relaxation peak is about 5 minutes (10 Hz–10 kHz with 20 data points). The obtained standard deviation of the magnetic signal at the relaxation frequency (around 100 Hz) is equal to about 10−5 (volume susceptibility SI units), which is in the same range obtained with the DynoMag system. The limit of detection with this method is found to be in the range of 1 pM.
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| 17. |
- Boikov, Iouri, 1949, et al.
(author)
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Atomic rearrangements at the TiO2-terminated (001)SrTiO3 surface and growth of thin LaMnO3 films
- 2013
-
In: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 102:5
-
Journal article (peer-reviewed)abstract
- SrTiO3 is commonly used as a substrate for growth of various oxide films. Different reconstructions at the SrTiO3 surface have been claimed. A question is whether these survive subsequent depositions of thin films and influence film properties. Medium energy ion scattering (MEIS) was used to probe structure and composition of the surface layer of a TiO2-terminated (001) SrTiO3 single-crystal substrate and 1-4 unit cell (u.c.) thick LaMnO3 epilayers. Aligned spectra indicate enrichment of Ti at the surface and a TiO2 double-layer (DL) configuration. The DL arrangement survives pulsed-laser deposition of LaMnO3 in a background of high oxygen pressure (5 x 10(-2) mbar) while it is destroyed at lower oxygen pressure (10(-4) mbar). Simulations of random MEIS spectra indicate substantial interdiffusion and La doping of the substrate surface but all interfaces are nevertheless insulating.
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| 18. |
- Boikov, Yu A., et al.
(author)
-
Structure and magneto-transport parameters of partially relaxed and coherently grown La0.67Ba0.33MnO3 films
- 2013
-
In: Physics of the Solid State. - 1063-7834 .- 1090-6460. ; 55:10, s. 2043-2050
-
Journal article (peer-reviewed)abstract
- X-ray diffraction (XRD) and medium-energy ion scattering (MEIS) have been used to reveal distortions in the crystal lattice of La0.67Ba0.33MnO3 (LBMO) films formed in relaxation of mechanical stresses. The LBMO films 25 nm thick have been prepared by laser deposition. The XRD and MEIS data obtained suggest that biaxially and mechanically elastically stressed LBMO layers grow coherently on LSATO substrates, whose crystal lattice parameter differs only weakly from the corresponding LBMO parameter, whereas in the bulk of manganite films grown on LaAlO3 substrates, stresses relax partially. Stresses do not relax in the LBMO interface about 4 nm thick adjoining LaAlO3. The electro- and magneto-transport parameters of partially relaxed LBMO films have been compared with those obtained for coherently grown manganite films with approximately the same tetragonal distortion of the lattice cell (a (aSyen)/a (aEuro-) = 1.024-1.030; a (aEuro-) and a (aSyen) are the unit cell parameters in the substrate plane and normal to it, respectively). At temperatures substantially lower than the Curie temperature, the electrical resistivity rho of LBMO films fits the relation rho = rho(0) + rho(1) T (2) + rho(2)(H)T (4.5); the coefficients rho(0) and rho(1) do not depend on temperature T and magnetic field, and rho(2) does not depend on temperature but almost linearly decreases with increasing magnetic field strength H. The coefficient rho(2) for partially relaxed LBMO films is substantially larger than that for coherently grown manganite layers.
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| 19. |
- Burger, Paul, 1997, et al.
(author)
-
Atomic Force Manipulation of Single Magnetic Nanoparticles for Spin-Based Electronics
- 2022
-
In: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 16:11, s. 19253-19260
-
Journal article (peer-reviewed)abstract
- Magnetic nanoparticles (MNPs) are instrumental for fabrication of tailored nanomagnetic structures, especially where top-down lithographic patterning is not feasible. Here, we demonstrate precise and controllable manipulation of individual magnetite MNPs using the tip of an atomic force microscope. We verify our approach by placing a single MNP with a diameter of 50 nm on top of a 100 nm Hall bar fabricated in a quasi-two-dimensional electron gas (q2DEG) at the oxide interface between LaAlO3 and SrTiO3 (LAO/STO). A hysteresis loop due to the magnetic hysteresis properties of the magnetite MNPs was observed in the Hall resistance. Further, the effective coercivity of the Hall resistance hysteresis loop could be changed upon field cooling at different angles of the cooling field with respect to the measuring field. The effect is associated with the alignment of the MNP magnetic moment along the easy axis closest to the external field direction across the Verwey transition in magnetite. Our results can facilitate experimental realization of magnetic proximity devices using single MNPs and two-dimensional materials for spin-based nanoelectronics. © 2022 The Authors.
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| 20. |
- Calvani, P., et al.
(author)
-
Infrared spectroscopy of two-dimensional electron systems
- 2019
-
In: European Physical Journal: Special Topics. - : Springer Science and Business Media LLC. - 1951-6401 .- 1951-6355. ; 228:3, s. 669-673
-
Journal article (peer-reviewed)abstract
- © 2019, EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature. We have used grazing-angle infrared spectroscopy with polarized radiation to detect the Berreman effect (BE) in the two-dimensional electron systems (2DES) which form spontaneously at two interfaces: one between an amorphous film LaAlO3 and its SrTiO3 substrate (LAO/STO), and another at the interface between the topological insulator (TI) Bi2Se3 and its sapphire substrate. In both systems we have thus extracted the 2DES parameters at different temperatures. In the quasi-2DES under amorphous LAO, the surface density ns is higher than under crystalline LAO, while the mobility is nearly the same and the thickness d is 7 nm. In ultrapure Bi2Se3 on sapphire, preliminary data provided d
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| 21. |
- Chang, S, et al.
(author)
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An electrowetting-based microfluidic platform for magnetic bioassays
- 2010
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In: The 14th International Conference on Miniaturized Systems for Chemistry and Life Sciences, MicroTAS 2010, 3-7 Oktober, Groningen, Neterlands. - 9781618390622 ; 2, s. 1331-1333
-
Conference paper (peer-reviewed)abstract
- Here we present our recent work on a droplet-based microfluidic device for manipulating microliter-sized droplets. By replacing the formerly used common dielectric SiO2 with Si3N4 and applying a 33 nm thick Teflon top layer to create a hydrophobic surface, we successfully lowered the actuation voltage from 450 V to 50 Vdc/40 Vac. Sputtered HfO2 with high dielectric constant was also investigated as an insulator, which could reproducibly yield thin defect-free insulation layers and lower the actuation voltage to less than 40 V.
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| 22. |
- Charpentier, Sophie, 1983, et al.
(author)
-
Induced unconventional superconductivity on the surface states of Bi2Te3 topological insulator
- 2017
-
In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 8:1
-
Journal article (peer-reviewed)abstract
- Topological superconductivity is central to a variety of novel phenomena involving the interplay between topologically ordered phases and broken-symmetry states. The key ingredient is an unconventional order parameter, with an orbital component containing a chiral p(x) + ip(y) wave term. Here we present phase-sensitive measurements, based on the quantum interference in nanoscale Josephson junctions, realized by using Bi2Te3 topological insulator. We demonstrate that the induced superconductivity is unconventional and consistent with a sign-changing order parameter, such as a chiral px + ipy component. The magnetic field pattern of the junctions shows a dip at zero externally applied magnetic field, which is an incontrovertible signature of the simultaneous existence of 0 and pi coupling within the junction, inherent to a non trivial order parameter phase. The nano-textured morphology of the Bi2Te3 flakes, and the dramatic role played by thermal strain are the surprising key factors for the display of an unconventional induced order parameter.
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| 23. |
- Cherednichenko, Serguei, 1970, et al.
(author)
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A room temperature bolometer for terahertz coherent and incoherent detection
- 2011
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In: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 1:2, s. 395 - 402
-
Journal article (peer-reviewed)abstract
- We present a novel room temperature bolometer with nanosecond response that can be used both for coherent and incoherent detection through the entire terahertz frequency range. A responsivity of up to 15 V/W, and a noise equivalent power (NEP) = 450 pW/Hz0.5 were measured at modulation frequencies from 0.5 kHz to 100 kHz. A conversion gain of -28 dB was demonstrated at an intermediate frequency of 20 MHz with a Local Oscillator power of 0.74 mW. Possible improvements of the bolometer characteristics are discussed.
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| 24. |
- Chukharkin Leonidovich, Maxim, 1980, et al.
(author)
-
Improvement of Ultra-Low Field Magnetic Resonance Recordings With a Multilayer Flux-Transformer-Based High-T-C SQUID Magnetometer
- 2013
-
In: Ieee Transactions on Applied Superconductivity. - : Institute of Electrical and Electronics Engineers (IEEE). - 1051-8223 .- 1558-2515. ; 23:3
-
Journal article (peer-reviewed)abstract
- We have developed a multilayer flux-transformer-based high-T-C SQUID (flip-chip) magnetometer that improves signal-to-noise-ratios (SNR) in ultra-low field magnetic resonance (ulf-MR) recordings of protons in water. Direct ulf-MR-based benchmarking of the flip-chip versus a standard planar high-T-C SQUID magnetometer resulted in improvement of the SNR by a factor of 2. This gain is attributable to the improved transformation coefficient (1.9 vs 5.3 nT/Phi(0)) that increased the signal available to the flip-chip sensor and to the lower noise at the measurement frequency (15 vs 25 fT/Hz(1/2) at 4 kHz). The improved SNR can lead to better spectroscopic resolution, lower imaging times, and higher resolution in ulf-MR imaging systems based on high-T-C SQUID technology. The experimental details of the sensors, calibration, and ulf-MR benchmarking are presented in this report.
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| 25. |
- Chukharkin Leonidovich, Maxim, 1980, et al.
(author)
-
Noise properties of high-T-c superconducting flux transformers fabricated using chemical-mechanical polishing
- 2012
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:4, s. Article Number: 042602 -
-
Journal article (peer-reviewed)abstract
- Reproducible high-temperature superconducting multilayer flux transformers were fabricated using chemical mechanical polishing. The measured magnetic field noise of the flip-chip magnetometer based on one such flux transformer with a 9 x 9 mm(2) pickup loop coupled to a bicrystal dc SQUID was 15 fT/Hz(1/2) above 2 kHz. We present an investigation of excess 1/f noise observed at low frequencies and its relationship with the microstructure of the interlayer connections within the flux transformer. The developed high-T-c SQUID magnetometers may be advantageous in ultra-low field magnetic resonance imaging and, with improved low frequency noise, magnetoencephalography applications.
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