共查询到20条相似文献,搜索用时 15 毫秒
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Vogel N Fischer J Mohammadi R Retsch M Butt HJ Landfester K Weiss CK Kreiter M 《Nano letters》2011,11(2):446-454
We apply colloidal lithography to construct stacked nanocrescent dimer structures with an exact vertical alignment and a separation distance of approximately 10 nm. Highly ordered, large arrays of these nanostructures are accessible using nonclose-packed colloidal monolayers as masks. Spatially separated nanocrescent dimers are obtained by application of spatially distributed colloids. The polarization dependent optical properties of the nanostructures are investigated in detail and compared to single crescents. The close proximity of the nanocrescents leads to a coupling process that gives rise to new optical resonances which can be described as linear superpositions of the individual crescents' plasmonic modes. We apply a plasmon hybridization model to explain the spectral differences of all polarization dependent resonances and use geometric arguments to explain the respective shifts of the resonances. Theoretical calculations are performed to support the hybridization model and extend it to higher order resonances not resolved experimentally. 相似文献
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Experiments on ultrathin anisotropic arrays of subwavelength optical antennas display out-of-plane refraction. A powerful three-dimensional (3D) extension of the recently demonstrated generalized laws of refraction and reflection shows that the interface imparts a tangential wavevector to the incident light leading to anomalous beams, which in general are noncoplanar with the incident beam. The refracted beam direction can be controlled by varying the angle between the plane of incidence and the antenna array. 相似文献
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The understanding of interaction forces between nanoparticles in colloidal suspension is central to a wide range of novel applications and processes in science and industry. However, few methods are available for actual characterization of such forces at the single particle level. Here we demonstrate the first measurements of colloidal interactions between two individual diffusing nanoparticles using a colorimetric assay based on plasmon hybridization, that is, strong near-field coupling between localized surface plasmon resonances. The measurements are possible because individual gold nanoparticle pairs can be loosely confined in an optical potential well created by a laser tweezers. We quantify the degree of plasmon hybridization for a large number of individual particle pairs as a function of increasing salt concentration. The data reveal a considerable heterogeneity at the single particle level but the estimated average surface separations are in excellent agreements with predictions based on the classical theory of Derjaguin, Landau, Verwey, and Overbeek. 相似文献
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Carlo Mennucci Debasree Chowdhury Giacomo Manzato Matteo Barelli Roberto Chittofrati Christian Martella Francesco Buatier de Mongeot 《Nano Research》2021,14(3):858-867
Multifunctional flexible Au electrodes based on one-dimensional(1D)arrays of plasmonic gratings are nanofabricated over large areas with an engineered variant of laser interference lithography optimized for low-cost transparent templates.Au nanostripe(NS)arrays achieve sheet resistance in the order of 20 Ohm/square on large areas(~cm2)and are characterized by a strong and dichroic plasmonic response which can be easily tuned across the visible(VIS)to near-infrared(NIR)spectral range by tailoring their cross-sectional morphology.Stacking vertically a second nanostripe,separated by a nanometer scale dielectric gap,we form near-field coupled Au/SiO2/Au dimers which feature hybridization of their localized plasmon resonances,strong local field-enhancements and a redshift of the resonance towards the NIR range.The possibility to combine excellent transport properties and optical transparency on the same plasmonic metasurface template is appealing in applications where low-energy photon management is mandatory like e.g.,in plasmon enhanced spectroscopies or in photon harvesting for ultrathin photovoltaic devices.The remarkable lateral order of the plasmonic NS gratings provides an additional degree of freedom for tailoring the optical response of the multifunctional electrodes via the excitation of surface lattice resonances,a Fano-like coupling between the broad localised plasmonic resonances and the collective sharp Rayleigh modes. 相似文献
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Processing effects in self-organized mesoporous silica materials 总被引:1,自引:0,他引:1
Lian-Zhou Wang Jian Yu Jian-Lin Shi Dong-Sheng Yan 《Journal of Materials Science Letters》1999,18(14):1171-1173
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Active electric control of highly efficient third harmonic generation was realized in an ultrathin nonlinear metasurface by using a nanocomposite consisting of gold nanoparticles dispersed in polycrystalline strontium titanate as the electro-optic material. Owing to the nonlinearity enhancement associated with the slow light effect, quantum confinement effect, and field-reinforcement, a high conversion efficiency of 3 × 10−5 was obtained, which is two orders of magnitude larger than previously reported efficiencies at comparable pump intensities. A modulation of 12% in the intensity of the third harmonic generation and a 30-nm shift in the transparency window center were achieved by varying the applied voltage from −30 V to zero. Our results pave the way toward the realization of multi-functional integrated photonic devices and chips based on metasurfaces. 相似文献
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Mojtaba Dehghani 《Journal of Modern Optics》2018,65(2):151-157
Tunable metasurfaces can be employed to physically or mechanically engineer and control electromagnetic wave properties like reflection and transmission and their associated spectral characteristics like resonance frequency. Here, we propose highly tunable and sensitive metasurfaces composed of an array of a nested double U-shaped (NDU) nanoresonators on elastic polydimethylsiloxane substrate, operating in infrared region. The mechanical deformation varies the spaces between the coupled resonator elements which in turn leads to corresponding variations in the equivalent capacitance and inductance between the U-shaped elements causing efficient tunability. In addition to the higher signal strengths, it is also reported that the resonant frequency of the proposed metasurface exhibits substantial spectral shift. The observed remarkable trends are adequately verified by the developed equivalent circuit model for the proposed NDU-structure. 相似文献
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Jamet M Barski A Devillers T Poydenot V Dujardin R Bayle-Guillemaud P Rothman J Bellet-Amalric E Marty A Cibert J Mattana R Tatarenko S 《Nature materials》2006,5(8):653-659
The emerging field of spintronics would be dramatically boosted if room-temperature ferromagnetism could be added to semiconductor nanostructures that are compatible with silicon technology. Here, we report a high-TC (>400K) ferromagnetic phase of (Ge,Mn) epitaxial layer. The manganese content is 6%, and careful structural and chemical analyses show that the Mn distribution is strongly inhomogeneous: we observe eutectoid growth of well-defined Mn-rich nanocolumns surrounded by a Mn-poor matrix. The average diameter of these nanocolumns is 3nm and their spacing is 10nm. Their composition is close to Ge(2)Mn, which corresponds to an unknown germanium-rich phase, and they have a uniaxially elongated diamond structure. Their Curie temperature is higher than 400K. Magnetotransport reveals a pronounced anomalous Hall effect up to room temperature. A giant positive magnetoresistance is measured from 7,000% at 30K to 200% at 300K and 9T, with no evidence of saturation. 相似文献
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A formation process for ordered, self-organized cobalt (Co) nanodots in diamond-like carbon (DLC) thin films deposited by magnetron sputtering in a plasma-assisted Ar/CH4 discharge is presented. episilon-Co dots -5 nm in diameter, separated by 1-2 nm DLC boundaries and arranged in hexagonal arrays were produced on Si substrates. The formation mechanism relies on a self-organization process which is based on surface energy minimization and local magnetic field interaction. The proposed plasma-assisted process presents a controlled and cost-effective bottom-up nanofabrication approach for the production of well-ordered magnetic nanodots based on self-organization. 相似文献
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We report on the formation of self-organized rows of pits in highly epitaxial La(2/3)Sr(1/3)MnO(3) thin films on top of substrates having different structural misfits by rf magnetron sputtering. The best-defined pits form in coherently grown films at a low misfit irrespective of its nature (tensile or compressive stress). It is also found that the pit rows align along the step edges, which indicates in-phase growth instability with the step edges, irrespective of the misfit. However, out-of-phase pit rows are also found when the terrace width increases due to a decrease of the miscut angle. Pit's volume scales inversely with the lattice mismatch suggesting that structural strain alone does not favor the formation of pits. The formation of pits is analyzed within a thermodynamic model. 相似文献
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Gold nanoparticles (GNPs) are stable in a number of linear polymer solutions, including poly(vinyl alcohol), poly(N-vinyl-2-pyrrolidone), hydroxyethyl cellulose, and poly(ethylene oxide) (PEO). Of these, PEO, with a wide range of molecular mass (from 0.3 to 8 MDa), is particularly attractive for exploring the interaction between the GNPs and polymer molecules. We have found that the colors of the GNPs are significantly different in PEO solutions at concentrations below and above entanglement threshold concentration (Phi*), which allows one to determine Phi* values for different sizes of PEO from the inflection points of the plots of the absorbance at 600 nm against the concentration of PEO. The Phi* values are close to those obtained by the viscosity measurements, showing the usefulness of this simple method. Transmission electron microscopy images have confirmed that the change in the absorbance is due to the aggregation and/or agglomeration of the GNPs in PEO solutions. 相似文献