11,340 results match your criteria high dielectric

High mobility field-effect transistors based on MoS2 crystal grown by the flux method.

Nanotechnology 2021 Apr 12. Epub 2021 Apr 12.

School of Electronic and Electrical Engineering, Sungkyunkwan University, 300 Chun chun dong, Jangan - gu, Suwon-city 440-746, KOREA, Suwon, Korea (the Republic of).

Two-dimensional (2D) molybdenum disulphide (MoS2) transition metal chalcogenides (TMDs) have great potential in optical and electronic device applications; however, the performance of MoS2 is limited by its crystal quality, which serves as a measure of defects and grain boundaries in the grown material. Therefore, high-quality growth of MoS2 crystals continues to be a critical issue. In this context, we propose the formation of high-quality MoS2 crystals via flux method. Read More

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Reduced Graphene Oxide/FeO/Polyaniline Ternary Composites as a Superior Microwave Absorber in the Shielding of Electromagnetic Pollution.

ACS Omega 2021 Apr 22;6(13):9164-9175. Epub 2021 Mar 22.

Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal, India.

The present work is focused on fabrication of reduced graphene oxide/iron(II/III) oxide/polyaniline (RGO/FeO/PANI) ternary composite by a hydrothermal method, its characterization, and application in the development of a high microwave absorbing shielding material. The RGO/FeO/PANI composite showed dramatic enhancement of dielectric loss and magnetic loss compared to FeO/PANI and RGO/FeO binary composites. This is ascribed to the embedment of more heterostructure phases. Read More

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Seeded Growth of Ultrathin Carbon Films Directly onto Silicon Substrates.

ACS Omega 2021 Apr 24;6(13):8829-8836. Epub 2021 Mar 24.

School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia.

The production of graphene films is of importance for the large-scale application of graphene-based materials; however, there is still a lack of an efficient and effective approach to synthesize graphene films directly on dielectric substrates. Here, we report the controlled growth of ultrathin carbon films, which have a similar structure to graphene, directly on silicon substrates in a process of seeded chemical vapor deposition (CVD). Crystalline silicon with a thermally grown 300 nm oxide layer was first treated with 3-trimethoxysilyl-1-propanamine (APS), which was used as an anchor point for the covalent deposition of small graphene flakes, obtained from graphite using the Hummers' method. Read More

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Directional Modulation of Exciton Emission Using Single Dielectric Nanospheres.

Adv Mater 2021 Apr 9:e2007236. Epub 2021 Apr 9.

Walker Department of Mechanical Engineering and Texas Materials Institute, The University of Texas at Austin, Austin, TX, 78712, USA.

Coupling emitters with nanoresonators is an effective strategy to control light emission at the subwavelength scale with high efficiency. Low-loss dielectric nanoantennas hold particular promise for this purpose, owing to their strong Mie resonances. Herein, a highly miniaturized platform is explored for the control of emission based on individual subwavelength Si nanospheres (SiNSs) to modulate the directional excitation and exciton emission of 2D transition metal dichalcogenides (2D TMDs). Read More

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Dielectric Engineered Two-Dimensional Neuromorphic Transistors.

Nano Lett 2021 Apr 9. Epub 2021 Apr 9.

Department of Chemistry, National University of Singapore, Singapore 117543, Singapore.

Two-dimensional (2D) materials, which exhibit planar-wafer technique compatibility and pure electrically triggered communication, have established themselves as potential candidates in neuromorphic architecture integration. However, the current 2D artificial synapses are mainly realized at a single-device level, where the development of 2D scalable synaptic arrays with complementary metal-oxide-semiconductor compatibility remains challenging. Here, we report a 2D transition metal dichalcogenide-based synaptic array fabricated on commercial silicon-rich silicon nitride (sr-SiN) substrate. Read More

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Self-Isolated Raman Lasing with a Chiral Dielectric Metasurface.

Phys Rev Lett 2021 Mar;126(12):123201

Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA.

The light sources that power photonic networks are small and scalable, but they also require the incorporation of optical isolators that allow light to pass in one direction only, protecting the light source from damaging backreflections. Unfortunately, the size and complex integration of optical isolators makes small-scale and densely integrated photonic networks infeasible. Here, we overcome this limitation by designing a single device that operates both as a coherent light source and as its own optical isolator. Read More

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Development and characterization of NbSn/AlO superconducting multilayers for particle accelerators.

Sci Rep 2021 Apr 8;11(1):7770. Epub 2021 Apr 8.

Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.

Superconducting radio-frequency (SRF) resonator cavities provide extremely high quality factors > 10 at 1-2 GHz and 2 K in large linear accelerators of high-energy particles. The maximum accelerating field of SRF cavities is limited by penetration of vortices into the superconductor. Present state-of-the-art Nb cavities can withstand up to 50 MV/m accelerating gradients and magnetic fields of 200-240 mT which destroy the low-dissipative Meissner state. Read More

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Low-loss metasurface optics down to the deep ultraviolet region.

Light Sci Appl 2020 Apr 9;9(1):55. Epub 2020 Apr 9.

Physical Measurement Laboratory, National Institute of Standards and Technology, 20899, Gaithersburg, MD, USA.

Shrinking conventional optical systems to chip-scale dimensions will benefit custom applications in imaging, displaying, sensing, spectroscopy, and metrology. Towards this goal, metasurfaces-planar arrays of subwavelength electromagnetic structures that collectively mimic the functionality of thicker conventional optical elements-have been exploited at frequencies ranging from the microwave range up to the visible range. Here, we demonstrate high-performance metasurface optical components that operate at ultraviolet wavelengths, including wavelengths down to the record-short deep ultraviolet range, and perform representative wavefront shaping functions, namely, high-numerical-aperture lensing, accelerating beam generation, and hologram projection. Read More

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Generic Structural Relaxation in Supercooled Liquids.

J Phys Chem Lett 2021 Apr 8:3685-3690. Epub 2021 Apr 8.

Institute of Condensed Matter Physics, Technical University of Darmstadt, 64289 Darmstadt, Germany.

One of the unsolved problems of dynamics in supercooled liquids are the differences in spectral shape of the structural relaxation observed among different methods and substances, and a possible generic line shape has long been debated. We show that the light scattering spectra of very different systems, e.g. Read More

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Diversity-oriented synthesis of polymer membranes with ion solvation cages.

Nature 2021 Apr 7;592(7853):225-231. Epub 2021 Apr 7.

Joint Center for Energy Storage Research, Lawrence Berkeley National Laboratory, Berkeley, CA, USA.

Microporous polymers feature shape-persistent free volume elements (FVEs), which are permeated by small molecules and ions when used as membranes for chemical separations, water purification, fuel cells and batteries. Identifying FVEs that have analyte specificity remains a challenge, owing to difficulties in generating polymers with sufficient diversity to enable screening of their properties. Here we describe a diversity-oriented synthetic strategy for microporous polymer membranes to identify candidates featuring FVEs that serve as solvation cages for lithium ions (Li). Read More

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Synthesis and characterization of Mg-Zn ferrite based flexible microwave composites and its application as SNG metamaterial.

Sci Rep 2021 Apr 7;11(1):7654. Epub 2021 Apr 7.

Department of Electrical Engineering, Qatar University, 2713, Doha, Qatar.

In this article, we propose SNG (single negative) metamaterial fabricated on Mg-Zn ferrite-based flexible microwave composites. Firstly, the flexible composites are synthesized by the sol-gel method having four different molecular compositions of MgZnFeO which are denoted as Mg, Mg Mg and Mg. The structural, morphological, and microwave properties of the synthesized flexible composites are analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and conventional dielectric assessment kit (DAK) to justify their possible application as dielectric substrate at microwave frequency regime. Read More

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Nitrogen-Coordinated CoS@NC Yolk-Shell Polyhedrons Catalysts Derived from a Metal-Organic Framework for a Highly Reversible Li-O Battery.

ACS Appl Mater Interfaces 2021 Apr 7. Epub 2021 Apr 7.

School of Materials Science and Engineering, Northeastern University, Shenyang 110819, PR China.

Transition-metal sulfides (TMS) are one of the most promising cathode catalysts for Li-O batteries (LOBs) owing to their excellent stabilities and inherent metallicity. In this work, a highly efficient mode has been used to synthesize Co@CNTs [pyrolysis products of metal-organic frameworks (MOFs)]-derived CoS(CoS)@NC. Benefiting from the special yolk-shell hierarchical porous morphology, the existence of Co-N bonds, and dual-function catalytic activity (ORR/OER) of the open metal sites contributed by MOFs, the CoS@NC-400/AB electrode illustrated excellent charge-discharge cycling for up to nearly 100 times at a current density of 0. Read More

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Atmospheric Pressure Mass Spectrometry Imaging Using Laser Ablation, Followed by Dielectric Barrier Discharge Ionization.

Anal Chem 2021 Apr 7. Epub 2021 Apr 7.

Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.

Mass spectrometry imaging (MSI) has become a powerful tool in diverse fields, for example, life science, biomaterials, and catalysis, for its ability of and real-time visualization of the location of chemical compounds in samples. Although laser ablation (LA) achieves high spatial resolution in MSI, the ion yield can be very low. We therefore combined an LA system with an ambient ion source for post-ionization and an atmospheric pressure (AP) inlet mass spectrometer to construct a novel AP-MSI platform. Read More

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Multiscale Heterogeneity Strategy in Piezoceramics for Enhanced Energy Harvesting Performances.

ACS Appl Mater Interfaces 2021 Apr 7. Epub 2021 Apr 7.

Faculty of Materials and Manufacturing, Key Laboratory of Advanced Functional Materials, Education Ministry of China, Beijing University of Technology, Beijing 100124, China.

Piezoelectric energy harvesters (PEHs) with piezoceramics as the core can convert low-frequency vibration energy that is ubiquitous in the environment into electrical energy and are at the frontier of research in the field of energy. The high piezoelectric charge coefficient () together with the large piezoelectric voltage coefficient () are essential for enhancing the energy harvesting performances of PEHs working on a nonresonant state. However, conventional doping and solid solution design strategies lead to the same increase or decrease trend of and dielectric permittivity ε, making it difficult to obtain a high value because = /ε. Read More

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"Insert-and-Go" Activated Carbon Electrode Tip for Heavy Metal Capture and In Situ Analysis by Microplasma Optical Emission Spectrometry.

Anal Chem 2021 Apr 7. Epub 2021 Apr 7.

Research Center for Analytical Sciences, Department of Chemistry, College of Sciences, Northeastern University, P.O. Box 332, Shenyang 110819, China.

The miniaturized optical emission spectrometry (OES) devices based on various microplasma excitation sources provide reliable tools for on-site analysis of heavy metal pollution, while the development of convenient and efficient sample introduction approaches is essential to improve their performances for field analysis. Herein, a small activated carbon electrode tip is employed as solid support to preconcentrate heavy metals in water and subsequently served as an inner electrode of the coaxial dielectric barrier discharge (DBD) to generate microplasma. In this case, heavy metal analytes in water are first adsorbed on the surface of the activated carbon electrode tip via a simple liquid-solid phase transformation during the sample loading process, and then, fast released to produce OES during the DBD microplasma excitation process. Read More

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Microwave-assisted high-efficiency degradation of methyl orange by using CuFeO/CNT catalysts and insight into degradation mechanism.

Environ Sci Pollut Res Int 2021 Apr 5. Epub 2021 Apr 5.

College of Environmental Science and Engineering, Hunan University, Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, People's Republic of China.

Microwave-assisted catalytic oxidation technology has become an effective technology for rapid removal of organic pollutants in wastewater. In this research, the removal of methyl orange (MO) from aqueous solution by CuFeO loaded on carbon nanotubes (CuFeO/CNTs) under microwave irradiation was studied. The effects of different loadings (1:2, 1:4, 1:8) of CuFeO on the dielectric loss, magnetic loss, dielectric loss factor, magnetic loss factor, and reflection loss of composite materials were studied. Read More

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Multifunctional metalens generation using bilayer all-dielectric metasurfaces.

Opt Express 2021 Mar;29(6):9332-9345

Optical metasurfaces exhibit unprecedented ability in light field control due to their ability to locally change the phase, amplitude, and polarization of transmitted or reflected light. We propose a multifunctional metalens with dual working modes based on bilayer geometric phase elements consisting of low-loss phase change materials (SbSe) and amorphous silicon (a-Si). In transmission mode, by changing the crystalline state of the SbSe scatterer, a bifocal metalens with an arbitrary intensity ratio at the telecommunication C-band is realized, and the total focusing efficiency of the bifocal metalens is as high as 78%. Read More

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Millijoule few-cycle pulses from staged compression for strong and high field science.

Opt Express 2021 Mar;29(6):9123-9136

Intense few-cycle laser pulses have a breadth of applications in high energy density science, including particle acceleration and x-ray generation. Multi-amplifier laser system pulses have durations of tens of femtoseconds or longer. To achieve high intensities at the single-cycle limit, a robust and efficient post-compression scheme is required. Read More

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Modeling of surface-induced second-harmonic generation from multilayer structures by the transfer matrix method.

Opt Express 2021 Mar;29(6):9098-9122

We analytically and numerically investigate surface second-harmonic generation (SHG) from a stack of dielectric layers. We develop a theoretical formalism based on the transfer matrix method for the calculation of the surface-driven second-harmonic radiation from multilayer structures and elaborate it for the case of ultrathin dielectric layers using a power series expansion to derive the effective surface nonlinear tensor for the whole stack. We show that for deeply subwavelength thicknesses of the layers the surface responses from all interfaces can efficiently sum up, leading to largely enhanced efficiency of SHG. Read More

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Stable 5-GHz fundamental repetition rate passively SESAM mode-locked Er-doped silica fiber lasers.

Opt Express 2021 Mar;29(6):9021-9029

A stable passively mode-locked Er-doped silica fiber laser with a fundamental repetition rate of up to 5 GHz is demonstrated, which, to the best of our knowledge, is the highest repetition rate for 1.5 μm semiconductor saturable absorber mirror (SESAM) mode-locked Er-doped silica fiber (EDF) lasers. A segment of commercially available EDF with a net gain coefficient of 1 dB/cm is employed as gain medium. Read More

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Macroscopic wave-optical simulation of dielectric metasurfaces.

Opt Express 2021 Mar;29(7):10879-10892

We propose a novel method for the wave-optical simulation of diffractive optical elements (DOEs) like metasurfaces or computer-generated holograms (CGHs). Existing techniques mostly rely on the assumption of local periodicity to predict the performance of elements. The utilization of a specially adapted finite-difference beam propagation method (BPM) allows the semi-rigorous simulation of entire DOEs within a reasonable runtime due to linear scaling with the number of grid points. Read More

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