Showing papers on "Plasmon published in 1997"
TL;DR: The surface-enhanced infrared absorption (SEIRA) as mentioned in this paper is a surface analytical tool that is very useful for in situ studies of electrode/electrolyte interfaces.
Abstract: Molecules adsorbed on evaporated thin metal films exhibit enormously strong infrared absorption. The thin metal films that exhibit the surface-enhanced infrared absorption (SEIRA) consist of metal particles much smaller than the wavelength of light. Electric field associated with the incident infrared radiation is enhanced via the excitation of localized plasmon of the particles, yielding the absorption enhancement. Preferential orientation and the change in absorption coefficient of molecules caused by chemisorption onto the metal surface provide additional enhancement. Most characteristic observations in SEIRA experiments are well explained by a simple electromagnetic theory. The infrared spectroscopy utilizing the SEIRA effect is promising as a new surface analytical tool. In particular, it is very useful for in situ studies of electrode/electrolyte interfaces. By the combined use of the attenuated-total-reflection technique, reactions and adsorption/desorption of molecules at the interfaces can be inv...
568 citations
TL;DR: In this paper, the surface plasmon damping induced by high excitation of the electron gas is studied in femtosecond pump-and-probe experiments on gold colloids embedded in a sol-gel matrix.
Abstract: The surface plasmon damping induced by high excitation of the electron gas is studied in femtosecond pump-and-probe experiments on gold colloids embedded in a sol-gel matrix. Optical excitation of single-particle interband transitions leads to a pronounced broadening of the surface plasmon line. A similar behavior is observed for resonant excitation of the surface plasmon. This broadening is the dominant optical nonlinearity of the system, and reflects the excitation-induced damping of the surface plasmon resonance. The time evolution of the damping rate follows that of the electronic scattering rate.
282 citations
TL;DR: A variant of surface plasmon resonance (SPR) spectroscopy has been developed that combines a greatly enhanced sensitivity and spectral resolution with the ability to directly measure anisotropies in refractive index and optical absorption coefficient in a dielectric film adsorbed onto the surface of the overcoating.
237 citations
TL;DR: In this paper, the spontaneous emission rate of Eu{sup 3+} ions depends upon both the distance from, and thickness of, a silver film, and it is shown that as the silver film thickness is reduced, the well established influence of the mirror on the spontaneous emissions is further modified.
Abstract: We have experimentally determined how the spontaneous emission rate of Eu{sup 3+} ions depends upon both the distance from, and thickness of, a silver film. We show that as the silver film thickness is reduced ({lt} 100 nm) the well established influence of the mirror on the spontaneous emission rate is further modified. By comparing our data to theory we show that this is due to the availability of an additional decay channel, the surface-plasmon polariton on the far side of the metal film. {copyright} {ital 1997} {ital The American Physical Society}
196 citations
TL;DR: In this paper, surface plasmon interactions on a finite silver layer are theoretically investigated using a coupled dipole formalism, where both probe and protrusions are considered as single dipolar particles and interference of locally excited surface plasmons can be detected by detecting the radiation emitted into the lower half-space at angles beyond the critical angle of total internal reflection (forbidden light).
Abstract: Surface plasmon interactions on a finite silver layer are theoretically investigated using a coupled dipole formalism. The studied system consists of several protruding particles located on the surface of the layer that are scanned with an optical probe. An optical scan-image of the silver surface is obtained by assigning the recorded far-field radiation to the momentary position of the optical probe. Both, probe and protrusions are considered as single dipolar particles. Interferences of the locally excited surface plasmons can be recorded by detecting the radiation emitted into the lower half-space at angles beyond the critical angle of total internal reflection (forbidden light). The resulting scan images show excellent agreement with recent experimental measurements. The theory of the coupled dipole formalism using Green’s functions of a layered reference system is outlined and electromagnetic properties of surface plasmons are discussed.
124 citations
01 Nov 1997
TL;DR: In this paper, the authors used optical spectroscopy experiments on free clusters in UHV and on the same clusters after embedding to separate the cluster-matrix interface effects from other cluster effects like shape and structure effects, nonlocal dielectric effects and cluster size effects.
Abstract: Metal clusters exhibit unique optical properties due to the excitation of Mie plasmon resonances. It is well known since decades that measured resonances of clusters, surrounded by some adsorbate, or some solid or liquid embedding material (as e.g., in colloidal systems), are often not described quantitatively by Mie's theory. Only recently, these discrepancies were traced back to complex physical and chemical influences of the cluster-matrix interlayer onto the optical response. They prove often to be more important than cluster size effects. These findings opened a new field of surface/interface research where deviations of measured Mie resonances from the predictions of Mie's theory are used as sensitive sensors for physical and chemical interface properties and processes in cluster-matter. By combining optical spectroscopy experiments on free clusters in UHV and on the same clusters after embedding, this method was calibrated to separate, quantitatively, the cluster-matrix interface effects from other cluster effects like shape and structure effects, nonlocal dielectric effects and cluster size effects. Among all metals, silver exhibits the most pronounced Mie resonances, so silver clusters were used as model systems and were embedded in a broad variety of solid and liquid embedding media, in course of the investigations reported in the present Progress Report. A theoretical description of the obtained data, based upon static and dynamic charge transfer processes of the cluster electrons into/out of adsorbate states is, however, only at its beginning. It allows to ascribe the extremely short decay times of the resonances of the order of 1 to 10 fs to phase relaxation processes; the decay times are in good correspondence with results of direct femtosecond-experiments.
121 citations
TL;DR: In this paper, a direct write ablation technique has been implemented in a photon scanning tunneling microscope setup, which allows us to study surface-plasmon (SP) scattering by in situ created individual surface defects, while the sizes and shapes of the defects are varied continuously.
Abstract: A direct-write ablation technique has been implemented in a photon scanning tunneling microscope setup. This combination allows us to study surface-plasmon (SP) scattering by in situ created individual surface defects, while the sizes and shapes of the defects are varied continuously. It is found that within a certain range of its size, a ``hill'' on an otherwise flat surface can be the source of a very narrow plasmon beam. This effect is explained using the Huygens-Fresnel principle. Shadowing and refraction of the SP field by smaller defects has also been observed. In order to explain these results we introduce an effective SP refractive index for two classes of surface defects: shallow topographical defects and areas covered with absorbed molecular layers. This concept allows us to achieve a qualitative understanding of plasmon scattering in many practical cases. Some simple optical elements for the control of SP propagation are suggested and demonstrated. Our observations suggest numerous practical applications in multichannel chemical sensing, biosensing, and integrated optics.
115 citations
TL;DR: In this article, the combination of small Au particles with NiO, CuO and CO3O4 films led to improved or new optical gas sensitivity via different mechanisms, which can be explained by the change in positive hole density change of NiO which was enhanced by an increase in catalytic formation and decomposition of surface carbonates with Au.
100 citations
TL;DR: In this article, a detailed study of the waveguide and plasmon polariton properties of four-layer systems involving highly doped semiconductor material is presented, and applications at wavelengths near the transition region and near the plasma wavelength are proposed and discussed.
Abstract: This paper presents a detailed study of the waveguide and plasmon polariton properties of four-layer systems involving highly doped semiconductor material. The dispersion relations of waveguide and plasmon polariton modes are calculated for different geometrical parameters and material properties. Special attention is paid to the transition region between the latter modes, which exhibits a complex behavior. Slab plasmon polaritons at wavelengths slightly larger than the plasma wavelength, yielding a positive real part of the permittivity, have been found. Finally, applications at wavelengths near the transition region and near the plasma wavelength are proposed and discussed.
94 citations
TL;DR: In this article, the Mie-Drude equation was interpreted by taking into consideration of a spilling out of electrons from the Au particle to the alumina matrix, and the measured values of χm(3) of the doped films are in the range of 9.2×10−6−4.0×10 −5 esu in the neighborhood of plasmon resonance wavelength of 530-570 nm.
Abstract: The precursor Au-doped alumina gel film was prepared by a sol-gel method using HAuCl4⋅4H2O and alumina sol derived from AlCl3⋅6H2O. The precursor gel was heat treated in a H2 gas flow at 300–800 °C. Average particle diameters of the Au particle of doped films were in the range of 4.6–12.7 nm. In the absorption spectra of the film, plasmon resonance absorption was strongly dependent on the heat treatment temperature of the alumina matrix, showing more sharp spectra and significant red shift with decreasing particle size. It was interpreted by a modified Mie–Drude equation by taking into consideration of a spilling out of electrons from the Au particle to the alumina matrix. The measured values of χm(3) of the doped films are in the range of 9.2×10−6–4.0×10−5 esu in the neighborhood of plasmon resonance wavelength of 530–570 nm. These are larger than those reported for the other doped systems. A dominant nonlinear response on the 1–3 ps time scale was obtained, reflecting higher thermoconductivity of alumin...
94 citations
TL;DR: In this paper, a two-phase liquid/liquid system was used to synthesize colloidal gold nanoparticles in toluene solution, synthesized using a two phase liquid-to-liquid system.
TL;DR: In this article, the authors measured a plasmon enhanced Coulomb drag in a GaAs/AlGaAs double quantum well electron system at temperatures comparable to the Fermi temperature.
Abstract: At temperatures comparable to the Fermi temperature, we have measured a plasmon enhanced Coulomb drag in a GaAs/AlGaAs double quantum well electron system. This measurement provides a probe of the many-body corrections to the coupled plasmon modes, and we present a detailed comparison between experiment and theory testing the validity of local field theories. Using a perpendicular magnetic field to raise the magnetoplasmon energy we can induce a crossover to single-particle Coulomb scattering.
TL;DR: In this article, the authors investigated the renormalizability of the classical φ4 theory at finite temperature and showed that it can be rendered finite by the counterterms of classical static theory.
TL;DR: In this paper, a system of Ag nanoparticles placed very close to an Al surface was prepared by depositing an Ag-$mathrm{SiO}}_{2}$ composite film on an Al film, and surface plasmon polaritons (SPP's) on the Al surface were excited by an attenuated total reflection (ATR) method and light emission from the SPP's caused by the presence of the particles was measured.
Abstract: A system of Ag nanoparticles placed very close to an Al surface was prepared by depositing an Ag-${\mathrm{SiO}}_{2}$ composite film on an Al film. Surface plasmon polaritons (SPP's) on the Al surface were excited by an attenuated total reflection (ATR) method and light emission from the SPP's caused by the presence of the Ag nanoparticles was measured. The intensity of emitted light was found to rapidly decrease as the distance between the particles and the surface increases. From a good qualitative agreement between experimental results and those of electromagnetic calculations, the following processes of light emission are suggested: (i) The SPP's excited by the ATR method excite the electromagnetic normal modes localized in between the Ag particles and the Al surface (gap modes), (ii) the gap modes then induce localized surface current on the Al surface, and (iii) the induced surface current emits light.
TL;DR: In this paper, a near-field optical microscope has been used for probing the surface plasmon fields on a smooth silver film with superimposed specifically designed nanoscale surface structures.
TL;DR: In this article, a comparative atomic force microscopic (AFM) analysis of as-deposited and annealed TSFs (aTSFs) was performed and it was found that uniform ellipsoidal roughness ∼41 × 25 nm in lateral cross section and ∼45 nm in height results after annealing.
Abstract: High-temperature annealing of thick silver films (TSFs) deposited onto a smooth dielectric substrate leads to high-order self-organization of metal clusters on the film surface. A comparative atomic force microscopic (AFM) analysis of “as-deposited” and annealed TSFs (aTSFs) shows that uniform ellipsoidal roughness ∼41 × 25 nm in lateral cross section and ∼45 nm in height results after annealing. These metal clusters are mutually oriented so that the main lateral axes of the ellipsoids are nearly parallel. UV−visible data demonstrate a ∼300 nm hypsocromic shift of the bands corresponding to the collective surface plasmon modes. Additionally, a new (∼350 nm) band related to the normal component of the plasmon oscillations appears after annealing. This band was found to be strongly angle-dependent for p-polarized light. The aTSFs appeared extremely time- and organic solvent-stable versus as-deposited films. The aTSFs were found to be nondisturbing surface-enhanced Raman scattering (SERS)-active substrates i...
TL;DR: In this article, the authors studied the electrical excitations of graphite layers within the random-phase approximation, and the calculated plasmon frequencies were consistent with the experimental measurements on graphite and stage-1 GICs.
Abstract: The \ensuremath{\pi}-electronic excitations of graphite layers are studied within the random-phase approximation. They principally reflect the \ensuremath{\pi}-band characteristics, the strong wave-vector dependence, the anisotropic behavior, and the special symmetry. The \ensuremath{\pi} plasmons in graphite have strong dispersion relations with the transferred momentum (q). They behave as an optical plasmon in a three-dimensional electron gas at small q. Moreover, the anisotropic behavior at the plane is apparent at large q. For a single graphite layer, the \ensuremath{\pi} plasmons would disappear at very small q, and their frequencies are obviously reduced. The absence of interlayer Coulomb interactions is the main reason for this. The stage-1 graphite intercalation compounds (GIC's), as compared with graphite, exhibit the richer excitation spectra and the lower \ensuremath{\pi}-plasmon frequencies. They have the intraband plasmon as well as the interband \ensuremath{\pi} plasmon. These two kinds of plasmons are quite different from each other in certain respects, e.g., the cause of the plasmon. The enhanced interlayer distances could effectively reduce the \ensuremath{\pi}-plasmon frequency, but not the transferred charges. The calculated plasmon frequencies are consistent with the experimental measurements on graphite and stage-1 GIC"s.
TL;DR: In this paper, the electron response of a cluster excited by femtosecond laser pulses was studied by means of a time-dependent density-functional method, and a strong correlation between induced electronic dipole oscillations and electron emission was observed, leading to a pronounced resonant enhancement of ionization when using lasers operating at the frequency of the Mie plasmon.
Abstract: We study the electron response of a cluster excited by strong femtosecond laser pulses by means of a time-dependent density-functional method. We investigate the full electronic dipolar response and multiphoton ionization processes. A strong correlation between induced electronic dipole oscillations and electron emission is observed, leading to a pronounced resonant enhancement of ionization when using lasers operating at the frequency of the Mie plasmon. We also examine the probabilities for producing differently charged ionic states of the system.
TL;DR: In this paper, a new Raman scattering peak at, located between the bulk TO and LO frequencies, has been observed in porous layers and attributed to a surface-related phonon, which is either the depletion of the GaAs skeleton due to the surface space charge effect or the decoupling of the LO-phonon and the plasmon modes at the relative large wavevectors transferred in nanostructures.
Abstract: Porous GaAs layers have been produced by anodic etching of (100)-oriented crystalline substrates in a solution. Scanning electron microscope images showed the formation of submicron pores, the average dimension of the remaining GaAs walls being of about 100 nm. Raman scattering by LO-phonon - plasmon coupled modes, inherent in as-grown crystals, was not observed in the porous layers. Proposed explanations are either the depletion of the GaAs skeleton due to the surface space-charge effect or the decoupling of the LO-phonon and the plasmon modes at the relative large wavevectors transferred in nanostructures. A new Raman scattering peak at , located between the bulk TO and LO frequencies, has been observed in porous layers and attributed to a surface-related phonon.
TL;DR: In this article, the angular distribution of second-harmonic light scattered from metal surfaces with weak random roughness is studied experimentally, and the power spectrum of the roughness has a rectangular form centered on the surface plasmon polariton wave number at the fundamental frequency, producing strong excitation of these surface waves.
Abstract: The angular distributions of second-harmonic light scattered from metal surfaces with weak random roughness are studied experimentally. The power spectrum of the roughness has a rectangular form centered on the surface plasmon polariton wave number at the fundamental frequency, producing strong excitation of these surface waves. The scattering distributions exhibit a pair of distinct peaks at angles consistent with the nonlinear interaction of the incident wave with fundamental plasmon polaritons. The controlled experiments allow a number of other scattering processes to be identified that include, for example, the nonlinear excitation of surface plasmon polaritons at the harmonic frequency. A peak in the second-harmonic distribution, predicted to appear in a direction perpendicular to the mean surface, is not observed.
TL;DR: In this paper, changes of the optical spectra are found if the clusters are covered by less than a molecular monolayer and diffusion of adsorbate molecules into the bulk of the particles can be identified.
Abstract: , N2O, CO2 or N2 on the particle surface. Depending on the molecules to which the clusters are exposed, different changes of the surface plasmon resonance in the spectra can be identified. The most essential experimental results are as follows. First, changes of the optical spectra are found if the clusters are covered by less than a molecular monolayer. Secondly, the observed variations of the spectra allow to distinguish between physisorption and chemisorption, i.e. characterize the strength of the surface chemical bond. Third, in sharp contrast to the usual shift of the plasmon frequency to longer wavelengths by change of the dielectric surrounding, a blue shift of the resonance has been observed upon dosage of CO2. Finally, diffusion of adsorbate molecules into the bulk of the particles can be identified.
TL;DR: In this article, interference of purely inelastically scattered electrons in the Gaussian image plane of an energy-filtering TEM (EFTEM) provides a means to measure the localisation of a specific inelastic scattering process.
TL;DR: In this paper, the intertube Coulomb interactions in a metallic multishell nanotube and a metallic nanotubes bundle have been included, and they have a strong effect on the low-frequency plasmon.
Abstract: A metallic carbon nanotube could exhibit a low-frequency plasmon, while a semiconducting carbon nanotube or a graphite layer could not. This plasmon is due to the free carriers in the linear subbands intersecting at the Fermi level. The low-frequency plasmon, which corresponds to the vanishing transferred angular momentum, belongs to an acoustic plasmon. For a smaller metallic nanotube, it could exist at larger transferred momenta, and its frequency is higher. Such a plasmon behaves as that in a one-dimensional electron gas (EGS). However, it is very different from the {pi} plasmons in all carbon nanotubes. Intertube Coulomb interactions in a metallic multishell nanotube and a metallic nanotube bundle have been included. They have a strong effect on the low-frequency plasmon. The intertube coupling among coaxial nanotubes markedly modifies the acoustic plasmons in separate metallic nanotubes. When metallic carbon nanotubes are packed in the bundle form, the low-frequency plasmon would change into an optical plasmon, and behave like that in a three-dimensional EGS. Experimental measurements could be used to distinguish metallic and semiconducting carbon nanotubes. {copyright} {ital 1997} {ital The American Physical Society}
TL;DR: In this article, the theory for the Auger transition rate of slow ions interacting with free-electron like metal surfaces reported previously is improved and applied to the calculation of the spectrum of the electrons emitted in the electron emission process.
TL;DR: In this article, the effect of roughening of the silver surface upon photoemission observed in the presence of two different scavengers dissolved in an aqueous solution, CO2 and NO3- ions, was re-examined.
Abstract: The effect of the roughening of the silver surface upon photoemission observed in the presence of two different scavengers dissolved in an aqueous solution, CO2 and NO3- ions, was re-examined. The quantum yield of the photocurrent exhibits a sharp maximum at 370−380 nm in the frequency range of surface plasmons on silver. These photoyields were strongly affected by the extent of the roughening of the Ag surface and reached an unusually large value of 0.05 electron per incident photon. Electrochemical oxidation/reduction roughening performed in the presence of Cl-, Br-, and ClO4- ions, similar to that employed in enhanced Raman scattering (SERS) experiments, affected the maximum of the photocurrent and in some cases also its onset potential. Photocurrents arising at potentials more negative than the potential of zero charge (pzc) of silver were principally influenced by changing morphology of the surface resulting from more or less deep roughening performed in different solutions. On the other hand, the ph...
TL;DR: In this article, plasmon excitation was found at an electron energy loss of 1.2 eV, both in the semiconducting and the metallic phase, in a thin polycrystalline VO 2 film.
TL;DR: In this paper, the suitability of a dielectric theory model to interpret the spectra is tested in the case of Al spheres and a similar model is applied to calculate excitation probabilities for carbon nanotubes.
Abstract: High resolution transmission electron microscopy and electron energy loss spectroscopy are used to investigate plasmon losses of aluminum nanospheres and carbon nanotubes with high spatial resolution. We observe that some features of the spectra depend on the size of the particles. The suitability of a dielectric theory model to interpret the spectra is tested in the case of Al spheres. The model permits the identification of the observed peaks and reproduces the size dependent fetures. A similar model is applied to calculate excitation probabilities for carbon nanotubes.
TL;DR: In this paper, the relaxation dynamics of coherent phonon-like LO-phonon-plasmon hybrid modes were investigated in $n$-doped GaAs using an infrared time-resolved coherent anti-Stokes Raman scattering technique.
Abstract: The relaxation dynamics of coherent phononlike LO-phonon--plasmon hybrid modes is investigated in $n$-doped GaAs using an infrared time-resolved coherent anti-Stokes Raman scattering technique. Measurements performed for different crystal temperatures in the range 10--300 K as a function of the electron density injected by doping show a large reduction of the hybrid mode dephasing time compared to the bare LO-phonon one for densities larger than ${10}^{16}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}.$ The results are interpreted in terms of coherent decay of the LO-phonon--plasmon mixed mode in the weak-coupling regime and yield information on the plasmon and electron relaxation. The estimated average electron momentum relaxation times are smaller than those deduced from Hall mobility measurements, as expected from our theoretical model.
TL;DR: In this paper, an energy loss spectroscopy-low energy electron diffraction (ELS-LEED) study of the electronic excitation spectrum of Ag(110) and Ag(111) is presented.
TL;DR: In this article, the authors studied the plasmon energy of Cs at a first-principles level and showed that the spatially localized 5p semicore shell induces a physical interplay between crystal local fields and electron correlations, leading to a novel, and relatively large, many-body shift of the PLASM energy.
Abstract: We study the dynamical electronic response of Cs at a first-principles level. The spatially localized 5p semicore shell induces a physical interplay between crystal local fields and electron correlations, leading to a novel, and relatively large, many-body shift of the plasmon energy. This effect, combined with that of oneelectron transitions into empty states near the plasmon energy, yields a plasmon dispersion curve which is in excellent agreement with experiment for small wave vectors. In addition, our results feature a flat dispersion for large wave vectors, in qualitative agreement with experiment. @S0163-1829~97!07504-8#