Showing papers on "Plasmon published in 1992"
TL;DR: Another type of optical near- field microscope, the scanning near-field ellipsometric microscope (SNEM), which achieves a resolution of a few nanometers and is applied to imaging of dye clusters and photooxidation of dyes.
Abstract: Recently we have introduced the scanning plasmon near-field microscope (SPNM) which achieves a resolution of a few nanometers. Resonantly excited extended surface plasmons generate an optical near-field which is locally probed by a sharp tip. The technique is applied to imaging of dye clusters and photooxidation of dyes. Here we present another type of optical near-field microscope, the scanning near-field ellipsometric microscope (SNEM).
279 citations
TL;DR: In this article, it was shown that the frequency dependence of a spherical shape is identical to that of a cubical boundary v = ( 3v F 4 ){1 + ( π 2 6 )( T e F ) 2 } is the average speed of a Fermi gas at temperature T.
141 citations
TL;DR: In this paper, Mie theory calculations of the optical spectrum (using the bulk optical constants of Au and Pb) yielded excellent agreement with the observed spectra for lead mantles thicker than 1 monolayer.
Abstract: Lead ions were reduced on the surface of colloidal gold particles (190 A in diameter) and the resulting bimetallic particles were investigated using spectrophotometry and electron microscopy. Deposition of lead adatoms causes the plasmon absorption band of gold to be shifted to shorter wavelengths, which is explained by Pb → Au electron donation and double layer charging. Three monolayers of lead are sufficient to produce the plasmon band of lead. Mie theory calculations of the optical spectrum (using the bulk optical constants of Au and Pb) yielded excellent agreement with the observed spectra for lead mantles thicker than 1 monolayer. The deposited lead is oxidized by oxygen, except for the first monolayer, which is produced by underpotential deposition. Similarly, lead atoms in the first layer are not oxidized by methyl viologen, whereas the atoms in the subsequent layers readily react. Experiments on the preparation of trimetallic particles (gold nucleus, lead layer, and outer cadmium layer) are also reported. © 1992 American Chemical Society.
124 citations
TL;DR: Experimental measurements have shown that there exists a surface-mode excitation at 3--4 eV, precisely localized on the external surface of the oxide layer, and Classical dielectric theory is used in interpreting these results, by invoking the presence of an ultrathin conductive layer.
Abstract: The study of the electronic properties of small particles is of major interest because of their intriguing physicochemical properties. The very small electron probes available in scanning transmission electron microscopes offer unique capabilities for investigating small particles with subnanometer spatial resolution. The correlation between electron-energy-loss spectra and energy-filtered images is of great help in pinpointing the excitations under study. This paper presents a theoretical and experimental study of collective excitation modes in the bulk and at the interfaces and surfaces of small spherical silicon particles covered with a thin oxide coating. Among other results, our experimental measurements have shown that there exists a surface-mode excitation at 3--4 eV, precisely localized on the external surface of the oxide layer. Classical dielectric theory is used in interpreting these results, by invoking the presence of an ultrathin conductive layer.
97 citations
01 Jan 1992
TL;DR: In this article, the response to light is described by the complex dielectric function e = e1(ω) + ie2(ω), where e is the frequency of the light wave.
Abstract: The optical constants of solids reflect their electronic and vibronic structure since the electromagnetic field of the light wave interacts with all fixed and mobile charges, i.e. with free electrons of the solid, with polarons, bound electrons, ions, polar phonons, plasmons etc. In general the response to light is described by the complex dielectric function e = e1(ω) + ie2(ω). For a degenerate semiconductor with Drude behaviour at small frequencies, a vibrational mode in the IR and a bandgap in the visible, the dielectric function has a frequency dependence of the form depicted in Fig. 4.1. Conversely, if the dielectric function is known, one can obtain information on the nature of the interactions or quasi-particles themselves and their optical transitions.
90 citations
TL;DR: In this article, electron energy-loss spectroscopy of carbon nanotubes was used to investigate the dielectric properties of graphite and showed that the peak energy of the π+σ plasmon energy varies from 22.0 eV to 24.5 eV.
Abstract: Carbon nanotubes were investigated by means of electron energy-loss spectroscopy. Two peaks due to the π plasmon and the π+σ plasmon were observed. The energy of the π+σ plasmon peaks varied from 22.0 eV to 24.5 eV, which roughly agrees with the average plasmon energy of graphite. A shoulder due to single electron excitations was observed at 13 eV, which was not observed in graphite. There were two kinds of nanotubes which exhibited their respective π plasmon peaks at 5.2 eV and 6.4 eV. The peaks in the dielectric function obtained by Kramers-Kronig analysis of the spectra were broader than those of graphite probably due to the curving of the graphitic sheets.
82 citations
TL;DR: The electron energy loss spectrum of C 60 in the gas phase from 1 to 30 eV is presented in this article, with shifts in the mutually observed bands seen only for the previously identified plasmon features.
82 citations
TL;DR: In this paper, electron energy loss spectroscopy attached to high-resolution transmission electron microscopy was used to investigate Si-clusters, and it was found that the plasmon energy increases in proportion to the inverse square of the cluster size.
Abstract: Plasmons in Si clusters were investigated by electron energy loss spectroscopy attached to high‐resolution transmission electron microscopy, by which an individual cluster can be investigated with the electron probe of 2 nm size. It has been found that the plasmon energy increases in proportion to the inverse square of the cluster size, and this is caused by the increase of the energy gap due to the quantum confinement effect.
70 citations
TL;DR: A simple phase-matching scheme, based on a resonant density modulation, is proposed and analyzed, and the nonlinear phase velocity and the renormalized electron mass due to plasmon screening are calculated.
Abstract: When an intense, plane-polarized, laser pulse interacts with a plasma, the relativistic nonlinearities induce a third-harmonic polarization. A phase-locked growth of a third-harmonic wave can take place, but the difference between the nonlinear dispersion of the pump and driven waves leads to a rapid unlocking, resulting in a saturation. What become third-harmonic amplitude oscillations are identified here, and the nonlinear phase velocity and the renormalized electron mass due to plasmon screening are calculated. A simple phase-matching scheme, based on a resonant density modulation, is then proposed and analyzed.
63 citations
TL;DR: The classical surface and interface modes of dotlike microstructures and the optical absorption corresponding to them are studied within a dielectric continuum approach and an integral-equation approach is introduced to treat dots having arbitrary shapes.
Abstract: The classical surface and interface modes of dotlike microstructures and the optical absorption corresponding to them are studied within a dielectric continuum approach. Explicit results are given mainly for the interface phonons of ionic materials, and it is noted that the same formalism applies to the surface plasmons of conducting materials. Analytical results for the modes are given for dots having the shapes of spheres and ellipsoids of revolution. An integral-equation approach is introduced to treat dots having arbitrary shapes. The dependence of the mode frequencies and eigenmodes on the dot shape and the dependence of the optical absorption on its shape and on the light polarization are discussed. An interesting feature that emerges is that the number of optically active modes increases as the dot shape becomes less symmetric. Dots with sharp tips are found to support interface modes which are strongly enhanced in the vicinity of the tip, a fact relevant to phenomena involving electric fields near the tip of a scanning microscope probe.
56 citations
TL;DR: In this paper, the interaction with bulk and surface modes of electrons emitted in the proximity of a solid surface was studied, taking into account the effects due to the sudden creation of the electron and residual atomic hole, and the finite distance to the surface.
TL;DR: In this paper, far infrared (FIR) studies of plasmons in spatially modulated two-dimensional electron gases (2DEGs) in AlGaAs/GaAs heterostructures using biased overlaid metal gratings including interdigitated gratings, both as optical couplers and as spatically modulating gates, were performed.
Abstract: We report far infrared (FIR) studies of plasmons in spatially modulated two‐dimensional electron gases (2DEGs) in AlGaAs/GaAs heterostructures using biased overlaid metal gratings, including interdigitated gratings, both as optical couplers and as spatially modulating gates. Comparison of the experimental results with the predictions of scattering matrix calculations of the FIR response of a modulated 2DEG in the presence of a perfectly conducting lamellar grating allow us to deduce the spatial variation of the number density distribution in the 2DEG as a function of grating bias. For the interdigitated grating gates, the 2DEG can be modulated at a period of twice that of the grating fingers by differentially biasing alternate fingers; 2D plasmon resonances have been observed at half‐integral values of the grating wave vector G, corresponding to the electrically induced periodicity of the 2DEG modulation itself acting as an optical coupler in addition to the metal grating. The observed G/2 plasmon frequencies decrease with increasing amplitude of the 2DEG number density modulation, in quantitative agreement with those obtained from scattering matrix calculations of the optical response of a modulated 2DEG under a perfectly conducting lamellar grating; calculations of the oscillating charge density profiles show that this occurs because, as the modulation amplitude increases, the oscillation becomes localized in regions of low 2DEG number density which are also under one of the sets of grating fingers, and is therefore better screened.
TL;DR: Measurements are reported of surface plasmon energy and dispersion carried out by electron energy loss spectroscopy on Ag(110) along both high-symmetry crystallographic directions with strong azimuthal dependence.
Abstract: Measurements are reported of surface plasmon energy and dispersion carried out by electron energy loss spectroscopy on Ag(110) along both high-symmetry crystallographic directions. For small q ∥ the data show a linear and positive dispersion with a strong azimuthal dependence that is twice as large along the (001) direction as along (110)
TL;DR: Specific recognition reactions of proteins at functionalized interfaces were observed with plasmon surface polariton (PSP) spectroscopy with good accessibility given in the case of a “diluted” presentation of the receptors at the interface.
TL;DR: This analysis shows how quantum size effects evolve into hydrodynamical classical size effects with increasing thickness of the film.
Abstract: Confinement of electrons in ultrathin metallic films leads to subbands. By increasing the thickness of the electron layer, the subbands will dissolve into a quasicontinuum, with the number of electrons per unit volume kept constant. Within the random-phase approximation, the two-dimensional plasmon, which originally follows Stern's dispersion relation, becomes a longitudinal surface plasmon. The plasmon excitations of a model metallic film are investigated by including all subbands. Single-particle excitations, which exhibit the depolarization shift, converge into the plasma excitation spectrum. With further increases in the film thickness, the bulk plasmon arises and the surface plasmon remains. Our analysis shows how quantum size effects evolve into hydrodynamical classical size effects with increasing thickness of the film.
TL;DR: In this article, a fiber optic surface plasmon resonance (SPR) sensor with a four-layer configuration is presented, which can achieve different dynamic ranges using the fourth layer which also gives toughness to the sensor configuration.
Abstract: A fibre optic surface plasmon resonance (SPR) sensor with a four-layer configuration is presented. Three-layer SPR sensors have been proposed before, but in many applications their dynamic range is not enough. Theoretical studies are carried out to achieve different dynamic ranges using the fourth layer which also gives toughness to the sensor configuration. Concentration data in different sensitivity and dynamic range situations are measured with four sensors in a fully automatized process where their operation is tested.
IBM1
TL;DR: In this article, light emission from Cu(111) and Au(110) surfaces in the scanning tunneling microscope has been characterized, and fluorescence spectra are interpreted as arising from inelastic tunneling excitation of radiative tip-induced plasmon modes.
TL;DR: In this paper, a differential equation for the polarizability of a small, continuum, spherically symmetric medium is developed in the local dielectric response approximation, which is used to examine the size dependence of the plasmon resonance absorption of small metal particles.
Abstract: A differential equation for the polarizability of a small, continuum, spherically symmetric medium is developed in the local‐dielectric‐response approximation The dynamic polarizability of a small metal sphere is then calculated through this equation using the Drude dielectric expression with the spatial dispersion of the free electron density given by the results of self‐consistent density functional calculations on jellium This approach is used to examine the size dependence of the plasmon resonance absorption of small metal particles It is able to account for the observed broadening and peak frequency shifts, both ‘‘red’’ and ‘‘blue,’’ as well as the additional absorption feature seen for small particles To the extent that comparison with experimental data is possible, good agreement is found
TL;DR: Strong enhancement of acoustic plasmons in optically excited nonequilibrium electron-hole plasmas in bulk semiconductors is shown to cause ultrashort dephasing times and very high carrier-carrier scattering rates.
Abstract: Strong enhancement of acoustic plasmons in optically excited nonequilibrium electron-hole plasmas in bulk semiconductors is shown to cause ultrashort (\ensuremath{\sim}10 fs) dephasing times and very high carrier-carrier scattering rates.
TL;DR: Two-dimensional plasmons in the monolayer graphite formed on TiC(111) surface have been detected by using electron energy loss spectroscopy as mentioned in this paper, which shows a peculir dispersion proportional to a square root of the wave vector parallel to the surface in the energy region of 0.3 eV.
IBM1
TL;DR: In this article, light emission observed from noble-metal surfaces in an STM has been interpreted as arising from inelastic tunneling excitation of radiative tip-induced plasmon modes.
TL;DR: Electromagnetic optical interactions between a small metal sphere and a metallic surface are studied by using a self-consistent approach in the presence of an external field to determine the intensity scattered by the metal particle for different polarizations of the incident field.
Abstract: Electromagnetic optical interactions between a small metal sphere and a metallic surface are studied by using a self-consistent approach in the presence of an external field. The intensity scattered by the metal particle is given for different polarizations of the incident field. This quantity, determined from a local treatment of the response function of the two interacting systems, exhibits a spatial dependence with respect to the approach distance close to that obtained from recent experimental studies. Moreover, at large separation, retardation effects included from a dipolar propagator give rise to pseudoperiodic oscillations such as the ones observed in reflection near-field optical microscopy. In the near-field range, plasmon modes of the whole system probe surface introduce narrow resonances in the scattered intensity versus the probe–sample separation.
TL;DR: In this article, the far-infrared optical response of a structure consisting of a perfectly conducting grating gate on a modulation-doped GaAs/AlGaAs heterojunction has been calculated using the scattering matrix technique.
Abstract: The far‐infrared optical response of a structure consisting of a perfectly conducting grating gate on a modulation‐doped GaAs/AlGaAs heterojunction has been calculated using the scattering matrix technique. The grating gate allows coupling between the incident radiation and the plasmon resonance of the two‐dimensional electron gas (2DEG) in such a system, but also modifies the dispersion relation for the plasmon because of screening by the image charge distribution induced on the grating gate. Using the scattering matrix technique allows this screening effect to be modeled more accurately than has hitherto been possible, and our calculations show that the induced charge is concentrated at the edges of the grating fingers. The sinusoidal profile of the oscillating charge density in the 2DEG distorts so that the maximum amplitude of the oscillation is close to these edges, and the plasmon frequency is determined by the amount of distortion of the plasmon charge density profile and the additional screening g...
TL;DR: In this experiment, diffraction gratings with periods between 70 and 100 nm provide the momentum for the slow mode to radiate, showing that it does contribute to the light emission.
Abstract: The emission of light from metal-oxide-metal tunnel junctions has been studied as a probe of the interaction of the tunneling current with the surface plasmon polaritons of the tunneling junction structure. The slow mode, with large fields in the oxide layer, is most directly coupled to the tunneling current. In this experiment, diffraction gratings with periods between 70 and 100 nm provide the momentum for the slow mode to radiate. We report the unambiguous measurement of the direct emission from the slow mode showing that it does contribute to the light emission.
TL;DR: In this article, the spectra of plasmon-polaritons are evaluated in semi-infinite superlattices composed of two-dimensional electron gas (2DEG) layers separated by dielectric media.
TL;DR: In this article, the Raman intensity from a benzene overlayer on a silver grating as a function of layer thickness both in theory and experiment is studied. And numerical results are obtained using matrix formalism based on the Rayleigh method for a coated grating.
Abstract: We study the Raman intensity from a benzene overlayer on a silver grating as a function of layer thickness both in theory and experiment. Numerical results are obtained using matrix formalism based on the Rayleigh method for a coated grating. The electromagnetic enhancement due to surface plasmon polariton resonances and multiple beam interferences for a p-polarized incident wave is discussed.
TL;DR: In this paper, photon emission induced by electron tunneling into a granular gold surface was investigated using a scanning tunneling microscope, and the intensity of light emission as a function of the applied bias voltage and observed resonance peaks at 1.9 and 2.7 V.
TL;DR: In this article, the authors investigated thin films of the quantum systems hydrogen and helium both in thermodynamic equilibrium and in metastable states and found that the film thickness and surface roughness are obtained from the excitation of surface plasmons and mobility measurements of surface state electrons.
Abstract: The authors report on investigations of thin films of the quantum systems hydrogen and helium both in thermodynamic equilibrium and in metastable states. Information about the film thickness and surface roughness is obtained from the excitation of surface plasmons and mobility measurements of surface state electrons. The equilibrium studies show triple-point wetting for H[sub 2] on Au substrates, in agreement with earlier results for similar systems. Unexpectedly, a distinct hysteretic behavior of the saturated film thickness is found near the triple-point. Superfluid [sup 4]He films on as prepared Ag display complete wetting. Investigations of H[sub 2] films in metastable states prepared by quench-condensation at 1.5K reveal pronounced changes in the film structure upon annealing. These changes set in far below the desorption temperature and are ascribed to surface diffusion.
TL;DR: In this paper, the interaction of plasmon surface polaritons (PSPs) with the tunneling junction of a scanning tunneling microscope (STM) has been investigated by measuring the current response to a modulated PLASmon excitation.
Abstract: The interaction of plasmon surface polaritons (PSPs) with the tunneling junction of a scanning tunneling microscope (STM) has been investigated by measuring the current response to a modulated plasmon excitation. From the dependence on modulation frequency, bias voltage, steady‐state current, and metal film structure it is concluded that it originates mainly from PSP‐induced heating and the associated expansion of the tunneling tip. The modulated current signal (or the equivalently modulated z‐piezo voltage after the feedback loop) can be recorded while scanning the surface by STM. The resulting PSP maps reflect the polycrystalline metal film structure on the scale of a few nanometers convoluted to some extent with the tip shape and the PSP field distribution. The latter can be used to differentiate between different metal films on the micrometer scale.