Showing papers on "Plasmon published in 1981"
TL;DR: In this article, surface-enhanced Raman scattering is observed from uniformly sized and shaped silver particles produced by evaporation of silver onto a lithographically produced microstructure, which can be shifted by changes in particle shape or surrounding dielectric constant in agreement with particle plasmon theories of surface Raman enhancement.
226 citations
TL;DR: In this article, the authors investigated the longitudinal collective spectrum of a spatially separated two-component, two-dimensional plasma using a generalized random-phase approximation and showed that the spatial separation between the two charge components makes it possible for the acoustic branch to move out of the electron-hole continua of both the components.
Abstract: Longitudinal collective spectrum of a spatially separated, two-component, two-dimensional plasma is investigated using a generalized random-phase approximation. Such plasmas can be realized in semiconductor heterojunctions, superlattices, and inversion or accumulation layers. In general two modes are found to exist: the one with energy proportional to $\sqrt{q}$ at long wavelengths is the usual optical plasmon and the other with energy proportional to $q$ at long wavelengths is the acoustic plasmon. It is shown that the spatial separation between the two charge components makes it possible for the acoustic branch to move out of the electron-hole continua of both the components provided it exceeds a critical value. Consequently the acoustic-plasmon mode is totally undamped at long wavelength. The dynamic structure factor of the system is analyzed and the feasibility of observing an acoustic plasmon in GaAs-${\mathrm{Ga}}_{x}{\mathrm{Al}}_{1\ensuremath{-}x}\mathrm{As}$ double quantum well is discussed.
198 citations
TL;DR: In this article, the frequency and temperature dependence of the intraband optical conductivity of the noble metals Cu, Ag and Au is measured and contributions of electron-electron scattering are assessed.
Abstract: The frequency and temperature dependence of the intraband optical conductivity of the noble metals Cu, Ag and Au is measured and contributions of electron-electron scattering are assessed. Optical measurements were performed at temperatures of 77, 295 and 425 K to obtain values of the Drude electron scattering rate with a linear dependence on temperature which may be attributed to electron-phonon scattering, and a quadratic dependence on photon energy, which is suggestive of electron-electron scattering but is a factor of two to three times greater than would be expected. Comparison of the optical data with dc electrical and thermal resistivity data which also show behavior attributed to electron-electron scattering reveals discrepancies of up to an order of magnitude. Other possible mechanisms for the frequency dependence, including absorptance, electron-surface plasmon interactions, a two-carrier model, and a structure dependence are considered, and it is concluded that the frequency dependence in the Drude scattering rates of the noble metals is not yet quantitatively understood
96 citations
TL;DR: In this article, photoacoustic observation of nonradiative decay of surface plasmons was made on the plasmon excited at a silver-air interface by the attenuated-total-reflection method.
Abstract: Photoacoustic observation of nonradiative decay of surface plasmons was made on the plasmons excited at a silver-air interface by the attenuated-total-reflection method. Analysis made in conjunction with simultaneously measured optical absorptance data allowed us to separate the radiative and nonradiative relaxations and determine their relative probabilities.
82 citations
TL;DR: In this article, the collective effects in the longitudinal component analogous to the plasma oscillations (plasmons) in Coulomb systems were identified and the transverse mode, by contrast, is strongly damped.
Abstract: Molecular-dynamics computations for point dipolar particles of the time-dependent polarization fluctuations allow evaluation of the dielectric properties. From these the collective effects in the longitudinal component (dipolarons) analogous to the plasma oscillations (plasmons) in Coulomb systems can be readily identified. The transverse mode, by contrast, is strongly damped.
73 citations
TL;DR: A survey of theoretical research on acoustic plasmons is given and prospects for the observation of these elusive modes are examined in this paper, where possible acoustic plasmon contributions to the transition temperatures of the superconducting A-15 compounds are considered.
Abstract: A survey of theoretical research on acoustic plasmons is given and prospects for the observation of these elusive modes are examined. Possible acoustic plasmon contributions to the transition temperatures of the superconducting A-15 compounds are considered. Directions for future experiments and theory are suggested.
67 citations
TL;DR: In this paper, the interaction of light with clusters and random distributions of metal hemispheroids on a perfect conducting flat surface is studied and significant SERS enhancements are found to arise from multiple plasmon contributions to the surface electromagnetic fields.
67 citations
TL;DR: In this article, the emission of light from silver gratings coated with dye monolayer assemblies was reported for the first time, and was identified by a characteristic polarization and dependence of wavelength on angle of emission in the plane perpendicular to the grooves of the grating.
Abstract: The emission of light from silver gratings coated with dye monolayer assemblies is reported for the first time. The monolayer assembly was laid down by the Langmuir–Blodgett dipping technique. When the grating is illuminated with s‐ or p‐polarized light, weak fluorescence from the dye monolayer is detected. In addition there is emission of light from all plasmon surface polariton modes with energy lower than that of the exciting light. This latter emission is identified by a characteristic polarization and dependence of wavelength on angle of emission in the plane perpendicular to the grooves of the grating. At energies within the absorption bands of the dye monolayer, this emission is shown to be enhanced.
67 citations
TL;DR: The optical properties of the noble metal copper were determined by computer fitting the experimentally obtained attenuated total internal reflection (ATR) spectra of its surface plasmon in the visible spectral region (0.42 to 0.63 μm) as mentioned in this paper.
Abstract: The optical properties of the noble metal copper are determined by computer fitting the experimentally obtained attenuated total internal reflection (ATR) spectra of its surface plasmon in the visible spectral region (0.42 to 0.63 μm). The dispersion curves of the surface plasmon resonance of copper are determined; they show that the resonance exists on the steep absorption edge of ϵ2 at 2.16 eV. This absorption edge, which is due to the d-band to Fermi level transition, causes the large shift in the location of the surface plasmon excitation from ϵ1(ωs) = −1 to ϵ1(ωs) = −4.7 and causes the true resonance to occur in the complex frequency plane.
34 citations
TL;DR: The surface and bulk plasmon satellites in photoemission from a core level were calculated in this article, treating the photoelectron quantum mechanically and including plasmer dispersion, giving featureless satellites at low electron kinetic energy.
28 citations
TL;DR: In this article, it was shown that inelastic scattering by electronic excitations from neighbouring beams in a systematic row should raise background but not interfere with diffraction contrast, and that in weak-beam techniques, inelastically scattering from neighbouring beam in a row should be allowed to interfere with the diffraction analysis.
TL;DR: In this paper, low-energy electron-loss spectroscopy is used to study collective surface excitations on accumulation layers on ZnO and a prominent loss peak is observed which shifts in energy with electron concentration.
Abstract: Low-energy\char22{}electron-loss spectroscopy is used to study collective surface excitations on accumulation layers on ZnO. A prominent loss peak is observed which shifts in energy with electron concentration. The results are well accounted for theoretically and provide direct evidence for the existence of two-dimensional plasmons.
TL;DR: In this article, the changes in the characteristic Ni(100) loss spectra in the presence of Na, K and Cs are interpreted as a result of large charge transfer to Ni.
TL;DR: When a gold grating is illuminated at an appropriate energy, polarization, and angle to excite a plasmon surface polariton (SP) all lower energy radiative SP states emit light as mentioned in this paper.
TL;DR: In this article, an electron energy loss spectroscopy (ELS) technique was used to examine thin SiO2 (up to 60 A) grown thermally on crystal Si (111) and (100) substrates.
Abstract: Thin SiO2 (up to ~60 A thick) grown thermally on crystal Si (111) and (100) substrates was examined without any destructive treatments such as ion sputtering and chemical etching by electron energy loss spectroscopy (ELS) technique. The non-destructive ELS measurements were based on an employment of tunable escape length (~10 to several tens A) of probing electrons with different energies of 0.2–2.3 keV. With incident energies above critical ones dependent on oxide thickness, the loss spectra indicated a new feature at the transition energy of ~7.7 eV, which was identified to be associated with the Si–SiO2 interface, probably interfacial plasmons of the Si–SiO2 couple. The possible presence of roughness or undulation in the Si–SiO2 interface, which was considered to be a sharp one in the chemical structure, was discussed.
TL;DR: Using the hydrodynamic jellium model, it was shown that a surface plasma oscillation excited at the surface of the semi-infinite metal induces a finite amount of angular momentum to the system, so that, it is conjectured that the surface plasmon has a spin quantum number S = 1 with definite polarization as discussed by the authors.
TL;DR: In this paper, the authors show that metal clusters manifest a large variety of interesting spectroscopic properties ranging from such phenomena as the extremely long vibrational lifetimes of transition metal dimers, to the extreme fluxionality of form of certain metal trimers to collective electronic oscillations (surface plasmons) in larger clusters which have achieved a measure of bulkness.
Abstract: We show that metal clusters manifest a large variety of interesting spectroscopic properties ranging from such phenomena as the extremely long vibrational lifetimes of transition metal dimers, to the extreme fluxionality of form of certain metal trimers to collective electronic oscillations (surface plasmons) in larger clusters which have achieved a measure of ’’bulkness’’. The last results in the distinctive color of colloids and in the greatly enhanced Raman scattering ability of molecules adsorbed on rough silver surfaces, the metal surface irregularities sustaining similar collective conduction electron oscillations as do colloidal particles. Absorptions due to these processes in silver surface bumps have been observed directly, using a scanning, stress‐modulator ellipsometric technique.
TL;DR: In this paper, the Mott transition from the electron-hole plasma to the excitonic state was observed using a streak camera and the plasmon sideband was identified.
TL;DR: In this paper, a simple hydrodynamic method for non-local screening at a metal surface, in which the surface polarisation charge is treated more realistically, was used to obtain good agreement with the frequency dependence of photoemission both from the Al(100) surface state, and from the Fermi level.
Abstract: A calculation of the photoemission from Al (100) and (111) surfaces, which includes band-structure effects but neglects screening of the photon field, gives good agreement with experimental results at fixed photon energy; it does not reproduce the observed variation in emission intensity from a fixed initial state as a function of photon frequency Treating Al as a free-electron gas with a frequency-dependent local dielectric function is also unsatisfactory However, using the simple hydrodynamic method for non-local screening at a metal surface, in which the surface polarisation charge is treated more realistically, the authors obtain good agreement with the frequency dependence of photoemission both from the Al(100) surface state, and from the Fermi level This shows enhancement in photoemission below the bulk plasmon frequency, and a minimum at omega p
TL;DR: In this article, the interaction of oxygen with polycrystalline aluminum sample has been studied using electron energy loss spectroscopy (ELS) and SES over a wide range of primary electron energies (30 ⊽ E p ⩽ 250 eV ).
TL;DR: In this article, the distance of the dye molecules from the metal surface was calibrated in the range (2.7÷29.5) nm by using the Langmuir-Blodgett monolayer technique.
Abstract: Nonradiative energy transfer from excited dye molecules adjacent to silver and gold surfaces has been investigated experimentally. By using the Langmuir-Blodgett monolayer technique, the distance of the molecules from the metal surface was calibrated in the range (2.7÷29.5) nm. Dye-plasmon surface polariton coupling was measured as a function of the metal-molecule separation by using attenuated-total-reflection technique. For an orientation of the transition dipole moment of the dye parallel to the metal surface and for nonresonant interaction, it was found that nonradiative energy transfer of fluorescing molecules to plasmon surface polaritons strongly depends on their distance from the metal surface. This decay channel becomes less efficient by approachingthe surface and eventually vanishes when the molecules are placed in the very vicinity of the metal film.
TL;DR: In this paper, an analytic expression for the change in the propagation constant of a surface plasmon, KΔβ, as a function of the dielectric constants of the two media, the nonlinear refractive index of the semiconductor, n2,E, and the power carried by the plasman is presented.
Abstract: A surface plasmon that is excited on the interface separating a metal and a nonlinear semiconductor has a propagation constant that depends on the power carried by the plasmon. We present an analytic expression for the change in the propagation constant of the plasmon, KΔβ, as a function of the dielectric constants of the two media, the nonlinear refractive index of the semiconductor, n2,E, and the power carried by the plasmon. We define a figure of merit, P0, which is the power required for shifting the phase of the plasmon by π/2 along a distance S, (S = 1/2α, where α is the plasmon decay constant), and find the wavelength dependence of KΔβ and P0.
TL;DR: In this article, a parallel intense photon (laser, microwave, etc.) beams?0,k0 and?1,k1 shone on a plasma with frequency separation equal to the plasma frequency?p is capable of accelerating plasma electrons to high energies in large flux.
Abstract: Parallel intense photon (laser, microwave, etc.) beams ?0,k0 and ?1,k1 shone on a plasma with frequency separation equal to the plasma frequency ?p is capable of accelerating plasma electrons to high energies in large flux. The photon beat excites through the forward Raman scattering large amplitude plasmons whose phase velocity is equal to (?0-?1)/(k0-k1), close to c in an underdense plasma. The plasmon electrostatic fields trap electrons and carry them to high energies: Maximum electron energy Wmax = 2mc2[1-(?0-?1)2/c2(k0-k1)2]-1~2mc2(?0/?p)2. The multiple forward Raman instability produces smaller and smaller frequency and group velocity of photons; thus the photons slow down in the plasma by emitting accelerated electrons (inverse Cherenkov process).
TL;DR: In this paper, the influence of the intercalation with pyridine on the optical properties of the host material 2H-NbS 2 has been investigated, and the optical joint density of states function OJDOS(ω) of intercalated material is well represented by a linear superposition of the OJ DOS of pure NbS2 and that of Pyridine, assuming this shift to be caused by a change in the charge density contributing to the d-band plasmon loss relative to the pure host material.
TL;DR: In this article, the authors derived the potential of the central atom as a function of the velocity of the photoelectron and derived the corresponding phaseshifts delta l. They showed a transition between a neutral-like behaviour at low energy and an ionic-like one at high energy.
Abstract: For pt.I see ibid., vol.9, p.1189 (1979). The dynamic screening model describing the relaxation of the conduction electrons after the absorption of an X-ray photon in a simple metal is extended to the physical situation of EXAFS. It is used to calculate the potential of the central atom as a function of the velocity of the photoelectron and to derive the corresponding phaseshifts delta l. They show a transition between a neutral-like behaviour at low energy and an ionic-like one at high energy. This transition takes place in the whole energy range (above about 1 keV) and not only around the threshold for plasmon emission. The authors deduce from these results the accuracy of the determination of distances that can be expected when using ionic phase-shifts in a metal. This precision is found to depend on two parameters: (i) the distance of the neighbouring atom; and (ii) the energy Emax of the higher part of the EXAFS spectrum. The problem of the transferability of phaseshifts is thus discussed in a more quantitative way. In addition, they obtain the reduction of the amplitude of the EXAFS oscillations due to plasmon losses; this amplitude is greater than the one which is predicted by the mean free path factor e-2R lambda /, because of the transient processes of the screening mechanism.
TL;DR: In this paper, the surface plasmon modes of Ag thin films were studied by the light scattering method in the thickness range down to 100 A. The observed thickness dependence of the resonance peaks was analysed in detail by the theory of Kretschmann.