In-band and out-of-band reflectance calibrations of the EUV multilayer mirrors of the Atmospheric Imaging Assembly instrument aboard the Solar Dynamics Observatory
Abstract not provided
36 MATERIALS SCIENCE↗
SEARCH · Engineering Papers
Results for “Multilayer”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Enhancing the phase stability of ceramics under radiation via multilayer engineering
This study provides a strategy to improve the phase stability of ceramic material under radiation through interface engineering.
36 MATERIALS SCIENCE↗
Superconductivity in an ultrathin multilayer nickelate
We report the appearance of superconductivity in single-unit-cell Nd 6 Ni 5 O 12 , exhibiting a transition temperature similar to that of thicker films. In situ synchrotron x-ray scattering performed during growth of the parent phase, Nd 6 Ni 5 O 16 , shows that the necessary layer-by-layer deposition sequence does not follow the sequence of the formula unit but an alternate order due to the relative stability of the perovskite unit cell. We exploit this insight to grow ultrathin Nd 6 Ni 5 O 16 heterostructures and conduct in situ studies of topotactic reduction, finding that formation of the square-planar phase occurs rapidly and is highly sensitive to reduction temperature, with small deviations from the optimum condition leading to inhomogeneity and the loss of superconductivity. The fluorite layer within the unit cell facilitates reduction by initially stabilizing the square-planar phase in the upper half of the unit cell. Our findings provide insight into growth of the Ruddlesden-Popper nickelates, highlighting the need for in situ studies of the metastable phases key to superconductivity.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Promotion of superconductivity in magic-angle graphene multilayers
Graphene moiré superlattices show an abundance of correlated insulating, topological, and superconducting phases. Whereas the origins of strong correlations and nontrivial topology can be directly linked to flat bands, the nature of superconductivity remains enigmatic. We demonstrate that magic-angle devices made of twisted tri-, quadri-, and pentalayer graphene placed on monolayer tungsten diselenide exhibit flavor polarization and superconductivity. We also observe insulating states in the tril- and quadrilayer arising at finite electric displacement fields. As the number of layers increases, superconductivity emerges over an enhanced filling-factor range, and in the pentalayer it extends well beyond the filling of four electrons per moiré unit cell. Our results highlight the role of the interplay between flat and more dispersive bands in extending superconducting regions in graphene moiré superlattices.
Science & Technology - Other Topics↗
Multilayer graphene stacks grown by different methods-thickness measurements by X-ray diffraction, Raman spectroscopy and optical transmission
X-ray diffraction, Raman spectroscopy and Optical absorption estimates of the thickness of graphene multi layer stacks (number of graphene layers) are presented for three different growth techniques. The objective of this work was focused on comparison and reconciliation of the two already widely used methods for thickness estimates (Raman and Absorption) with the calibration of the X-ray method as far as Scherer constant K is concerned and X-ray based Wagner-Aqua extrapolation method.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Low-Voltage Scanning Electron Microscopy and Energy-Dispersive X-Ray Microanalysis of the Interface of Multilayer Polymer Composite
The morphology of the layer of polyelectrolyte complex, which is formed in the composite based on chitosan and sulfoethyl cellulose during the contact of a solution of one of them with a gel film of the other one, has been investigated by the low-voltage (≤3 kV) scanning electron microscopy. A technique for eliminating the effects related to charge accumulation on the dielectric film surface is proposed.
36 MATERIALS SCIENCE↗
Theoretical model for thin ferroelectric films and the multilayer structures based on them
A modified Weiss mean-field theory is used to study the dependence of the properties of a thin ferroelectric film on its thickness. The possibility of introducing gradient terms into the thermodynamic potential is analyzed using the calculus of variations. An integral equation is introduced to generalize the well-known Langevin equation to the case of the boundaries of a ferroelectric. An analysis of this equation leads to the existence of a transition layer at the interface between ferroelectrics or a ferroelectric and a dielectric. The permittivity of this layer is shown to depend on the electric field direction even if the ferroelectrics in contact are homogeneous. The results obtained in terms of the Weiss model are compared with the results of the models based on the correlation effect and the presence of a dielectric layer at the boundary of a ferroelectric and with experimental data.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Erratum to: “interlayer coupling in Fe/Cr/Gd multilayer structures” [journal of experimental and theoretical physics 120, 1041 (2015)]
No abstract prepared.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Nonspecular X-Ray Scattering from a Planar Phospholipid Multilayer
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99 GENERAL AND MISCELLANEOUS↗
Study of Light Neutron-Rich Nuclei Using a Multilayer Semiconductor Setup
The characteristics of two modifications of the semiconductor (s.c.d.) setup consisting of telescopes on the basis of silicon detectors are presented. These settings allow performing a precision measurement of energy in a large dynamic range (from a few to hundreds of MeV) and particle identification in a wide range of masses. The issues of measurement of the characteristics of s.c.d. telescopes and their impact on the quality of the obtained experimental data are considered. Considerable attention is paid to the use of created semiconductor devices for the search for and spectroscopy of light exotic nuclei on the accelerators of PNPI (Gatchina) and LANL (Los Alamos).
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Influence of irradiation with swift heavy ions on multilayer Si/SiO{sub 2} heterostructures
The influence of Xe ions with an energy of 167 MeV and a dose in the range 10{sup 12}-3 Multiplication-Sign 10{sup 13} cm{sup -2} on heterostructures consisting of six pairs of Si/SiO{sub 2} layers with the thicknesses {approx}8 and {approx}10 nm, correspondingly, is studied. As follows from electron microscopy data, the irradiation breaks down the integrity of the layers. At the same time, Raman studies give evidence for the enhancement of scattering in amorphous silicon. In addition, a yellow-orange band inherent to small-size Si clusters released from SiO{sub 2} appears in the photoluminescence spectra. Annealing at 800 Degree-Sign C recovers the SiO{sub 2} network, whereas annealing at 1100 Degree-Sign C brings about the appearance of a more intense photoluminescence peak at {approx}780 nm typical of Si nanocrystals. The 780-nm-peak intensity increases, as the irradiation dose is increased. It is thought that irradiation produces nuclei, which promote Si-nanocrystal formation upon subsequent annealing. The processes occur within the tracks due to strong heating because of ionization losses of the ions.
36 MATERIALS SCIENCE↗
Multilayer heterostructures for quantum-cascade lasers operating in the terahertz frequency range
The results obtained in a study of the structural and optical properties of GaAs/AlGaAs heterostructures with 228 quantum cascades, grown by molecular-beam epitaxy, and in a simulation of interband optical transitions and transitions between the energy levels of a cascade are presented.
36 MATERIALS SCIENCE↗
Cleaved-edge photoluminescence spectroscopy of multilayer heterostructures
The capabilities of a technique based on combined photoluminescence and Raman-spectroscopy measurements upon lateral scanning across the cleaved edge of heterostructures for monitoring the strain profile and the thickness of epitaxial layers are demonstrated. The characteristics of a laser heterostructure with InGaAs/GaAsP quantum wells are investigated by this technique. It is shown that photoluminescence from different layers of the structure can be recorded separately. It is established that both the frequency of the InP-like phonon mode and the photoluminescence energy can be used to determine the composition of the In{sub x}Ga{sub 1–x}P alloy. The two methods yield close results.
36 MATERIALS SCIENCE↗
Infrared Reflection Spectra of Pb{sub 1–x}Sn{sub x}Se (x = 0.2, 0.34) Topological Insulator Films on a ZnTe/GaAs Substrate and the Vibrational Modes of Multilayer Structures
The reflectance spectra of the topological insulator Pb{sub 1–x}Sn{sub x}Se (x = 0.2, 0.34) films grown by molecular-beam epitaxy on a ZnTe/GaAs substrate are measured in the range of 12–2500 cm{sup –1} at room temperature. Using dispersion analysis, the frequencies of transverse optical phonons, plasma frequencies, highfrequency permittivities, and layer thicknesses are determined. In the quasi-steady-state approximation, the interface mode frequencies of the four-layer structure are calculated as a function of the overlap parameter χ{sub 1} (0 ≤ χ{sub 1} ≤ 1). The parameter describes the degree of overlap of two interface modes localized at planes bounding the layer to the right and left. The existence of interacting interface modes in the structure makes its spectrum different from the sum of component spectra. These differences manifest themselves in the experiment. The conditions of the interaction of interface modes with IR radiation are discussed.
36 MATERIALS SCIENCE↗
Multilayer Quantum Well–Dot InGaAs Heterostructures in GaAs-based Photovoltaic Converters
GaAs photovoltaic converters containing quantum well-dot (QWD) heterostructures are studied. The QWD properties are intermediate between those of quantum wells (QWs) and quantum dots. The QWDs are obtained by the epitaxial deposition of In{sub 0.4}Ga{sub 0.6}As with a nominal thickness of 8 single layers by metal-organic vapor phase epitaxy. QWDs are a dense array of elastically strained islands that localize carriers in three directions and are formed by a local increase in the indium concentration and/ or InGaAs-layer thickness. There are two quantum-well levels of varied nature in structures with QWDs. These levels are manifested in the spectral characteristics of GaAs photovoltaic converters. A short-wavelength peak with a maximum at around 935 nm is associated with absorption in the residual QW, and the long-wavelength peak (1015–1030 nm) is due to absorption in the QWDs. Investigation by transmission electron microscopy demonstrates that an increase in the number of InGaAs layers leads to stronger elastic stresses, which, in turn, increases the carrier confinement energy in the QWDs and lead to a corresponding long-wavelength shift of the internal quantum efficiency spectrum.
36 MATERIALS SCIENCE↗
The Field Effect in a Metal–Ferroelectric–Semiconductor System of Multilayer Ferroelectric Films with Various Structure Types
The ability to grow the interfacial defect-poor Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6} + Ba{sub 0.2}Sr{sub 0.8}TiO{sub 3} and Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3} + Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3} ferroelectric films onto the doped silicon substrates is discussed. A study of piezo-response via the quasi-static method (using the electrode area of 0.07 mm{sup 2}) reveals that heterostructures possess an initial polarized ferroelectric state with a spontaneous polarization vector perpendicular to the substrate at any type of Si conductivity. The polarized state is established to refer to two-dimension stresses in the ferroelectric, which is tunable through a preprepared Ba{sub x}Sr{sub 1–x}TiO{sub 3} onto a sublayer substrate as well as to a thickness of this sublayer. Polarization switching in Sr{sub 0.5}Ba{sub 0.5}Nb{sub 2}O{sub 6}/Si and Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3}/Si heterostructures under the external field arises at only using the barium–strontium titanate sublayer predeposited onto silicon. A 15% decrease in switching polarization in Ba{sub 0.8}Sr{sub 0.2}TiO{sub 3}/Ba{sub 0.4}Sr{sub 0.6}TiO{sub 3}/Si structures is observed after 500 h.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Optical Properties of Multilayer BaTiO{sub 3}/SiO{sub 2} Film Structures Formed by the Sol–Gel Method
Multi-layer film structures BaTiO{sub 3}/SiO{sub 2} with a thickness of ~1 μm containing up to 14 pairs of layers were synthesized by the sol–gel method with sequential heat treatment. It is shown that the synthesized structures are X-ray amorphous. The formation of bands in the transmission and reflection spectra caused by interference effects is demonstrated. A more regular structure exhibits a photon band gap (opacity band) in the visible range with main minimum at 636 nm and corresponding maximum in the reflection spectra. Dispersion characteristics of barium titanate films with different concentrations of initial sols were studied and an increase in the refractive index with an increase in the concentration of sol was demonstrated. For a sol with a concentration of 60 mg/mL, the refractive index in the spectral range of 390–1600 nm is 1.88–1.81. The prospects of sol–gel technology for the formation of BaTiO{sub 3}/SiO{sub 2} structures for nanophotonics and solar radiation converters are discussed.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗