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The 1.7 kV 4H-SiC MOSFET which features optimized retrograded-profile ion implantation in the JFET regions (RG-MOS) is proposed and fabricated on the 4 inch wafers. The measured results quantify the benefits of the RG-MOS structure: simultaneous improvement in high-frequency figures of merit (HF-FOM) (R on× C GD) by 1.5×, HF-FOM (R on × Q GD) by 1.5× and Baliga figure of merit (BFOM = 4BV2/ R on,sp) by 1.6× compared with the conventional MOSFET (CON-MOS). Unlike other reported complicated structures which need high-precise fabricating process, the proposed RG-MOS structure is compatible with the prior planar 4H-SiC MOSFET process, and is favorable for large-scale production. [ABSTRACT FROM AUTHOR]

The concentration dependence of the fluorescence spectra and lifetimes of chlorophyll a and sodium magnesium chlorophyllin are compared to explore the influences of intramolecular relaxation and intermolecular interaction of chlorophylls on the fluorescence dynamics. With different concentrations of chlorophyll a and sodium magnesium chlorophyllin in the suspensions, three different fluorescence emission bands are observed. Intermolecular interactions increase as the concentrations increase, which lead to redshifts in both fluorescence and lifetime spectra. Additionally, the lifetime is increased by re-absorption in the sodium magnesium chlorophyllin suspensions. These observations increase the understanding of the light harvesting and energy relaxation mechanisms of chlorophyll molecules. [ABSTRACT FROM AUTHOR]

ZnWO4 and ZnWO4:Eu3+ particles were prepared by refluxing in water solution using polyethylene glycol as a capping agent and then annealed at different temperatures. The samples were characterized by X-ray diffraction, Raman spectra, field-emission scanning electron microscopy, and cathodoluminescence spectra. The as-prepared amorphous samples annealed at high temperature (500-700°C) are sanmartinite structure of ZnWO4, and the spherical morphologies are basically retained, except for the increase of the particles size (from 28 to 56 nm). The low-voltage luminescent properties of these tungstate phosphors can be tuned by the doping of Eu3+ ions and annealing treatment. ZnWO4 and ZnWO4:Eu3+ particles annealed at 500°C or above exhibit strong blue-green and white light emission under the excitation of low-voltage electron beams, respectively, the former originating from the intrinsic WO66- complex, and the latter due to the combination of the emissions arising from the intrinsic WO66- and doped Eu3+ ions. The as-prepared ZnWO4:Eu3+ particles only emit a red light resulting from the 5D0 → 7FJ (J = 1, 2, 3, 4) transitions of Eu3+ ions. [ABSTRACT FROM AUTHOR]

The nanostructured Au/AgxO/Ag sandwich multilayer films on quartz substrates are prepared by the magnetron sputtering method. The morphology, plasmon resonance and surface enhanced Raman scattering (SERS) activities of the multilayer films are studied. The resonant absorption wavelength of localized surface plasmon is tuned in a wide range from 618 nm to 993 nm by controlling the density of nanoparticles of Au and Ag. The SERS activity of the Au/AgxO/Ag multilayer films are enhanced over ∼10 times compared with those of bare Ag and bare Au films. These properties may find a potential application in biosensor and bioimaging. [ABSTRACT FROM AUTHOR]

We theoretically demonstrate that pure magnetic quadrupole (MQ) scattering is achieved via the excitation of anapole modes and Fano resonance in noble metal (Au or Ag) and high refractive index dielectric (AlGaAs) hybrid nano-antennas. In Au-AlGaAs hybrid nano-antennas, electric anapole and magnetic anapole modes are observed, leading to the suppressions of electric and magnetic dipoles. Introducing gain material to AlGaAs nanodisk to increase the strength of electric quadrupole (EQ) Fano resonance leads to the suppression of EQ scattering. Then, ideal MQ scattering is achieved at the wavelength of total scattering cross-section dip. The increase of signal-to-noise ratio of MQ results in the great enhancement of near-field inside AlGaAs nanodisk. Additionally, the strong MQ resonance exhibits great capability for boosting second-harmonic generation by proper mode matching. These findings achieved in subwavelength geometries have important implications for functional metamaterials and nonlinear photonic nanodevices. [ABSTRACT FROM AUTHOR]

Electron transport driven by a temperature gradient in a transport junction constructed by connecting a zigzag hexagonal boron nitride (h-BN) nanoribbon between two graphene nanoribbons (Gr/BN/Gr) is studied by density functional calculations and non-equilibrium Green’s function method. When the zigzag-edged graphene nanoribbons are in the ferromagnetic configuration, the BN barrier introduces a spin-dependent scattering and causes an ‘X’-type spin-dependent transmission functions around the Fermi level at equilibrium. In a linear response approximation, this gives rise to a Seebeck thermopower with opposite signs for different spins. It drives electrons with different spins to flow in opposite directions under a finite temperature gradient. Calculations show that the charge current is zero while spin current is not, thus pure spin current is generated. These findings suggests the great importance of BN barrier in the generation of thermal spin current using graphene and the idea should be taken into consideration in the design of spintronic devices using two dimensional materials. [ABSTRACT FROM AUTHOR]

Zigzag-edged graphene and h-BN nanoribbons with passivated edges in the ground state are either spin-degenerate or spin-unpolarized systems, which are not directly applicable for spin-polarized transport. In this work, based on density functional calculations, we demonstrate that the combination of them to form van der Waals (vdW) heterostructures can be adopted to realize fully spin polarized transport. As an example, the ballistic transport properties of a zigzag-edged graphene nanoribbon (ZGNR) with six zigzag carbon chains is studied first with each lead as a vdW heterostructure formed by attaching a h-BN monolayer to each side of the ZGNR with AA-stacking. A greatly decreased transmission gap (0.28 eV) in one spin and a greatly increased transmission gap (0.82 eV) in the other spin is achieved in the transmission function, resulting in fully spin polarized transport at low bias. This arises from the stagger potential imposed by the h-BN layers, which not only exists in the leads, but also extends to the channel region. It changes the energy of the edge states of different spins localized at different sublattices in an opposite way in the whole device. The transmission gap and the threshold voltage can be further modulated by applying a vertical pressure to the vdW leads to tune the strength of the stagger potential or simply by changing the ribbon width. Finally, the increase of the channel length will greatly reduce the magnitude of the transmission around the Fermi level and the transmission gap will eventually recover the value of the band gap of the pristine ZGNR. These findings not only provide a novel way for achieving fully spin polarized transport in graphene, but also demonstrate the great importance of vdW heterostructures in the design of spintronic devices. [ABSTRACT FROM AUTHOR]

We theoretically study the properties of optical losses in a plasmonic multimer and find modes with lower radiative losses due to the cancellation of the dipole moment. High order plasmonic resonances, including electric quadrupole and magnetic dipole resonances, can be achieved by the reduction of symmetry in a multimer. Meanwhile, the dipole moment can be significantly reduced in these high order modes, and consequently, the radiative losses decrease efficiently. The low-loss modes can lead to a lower gain threshold in the gain-assisted nanosystem. In particular, compared with the electric dipolar mode in a single nanoshell, the gain threshold of the electric quadrupolar and magnetic dipolar modes in a multimer can drop by 57.66% and 59.22%, respectively. On the other hand, the gain threshold can reflect the extent of the optical losses of the plasmonic mode in a nanosystem. These findings may have potential applications in the design of a nanolaser, plasmon waveguide and photo-thermal device. [ABSTRACT FROM AUTHOR]

The transport properties of a single plasmon interacting with a hybrid system composed of a semiconductor quantum dot (SQD) and a metal nanoparticle (MNP) coupled to a one-dimensional surface plasmonic waveguide are investigated theoretically via the real-space approach. We considered that the MNP–SQD interaction leads to the formation of a hybrid exciton and the transmission and reflection of a single incident plasmon could be controlled by adjusting the frequency of the classical control field applied to the MNP–SQD hybrid nanosystem, the kinds of MNPs and the background media. The transport properties of a single plasmon interacting with such a hybrid nanosystem discussed here could find applications in the design of next-generation quantum devices, such as single-photon switching and nanomirrors, and in quantum information processing. [ABSTRACT FROM AUTHOR]