共查询到20条相似文献,搜索用时 46 毫秒
1.
A quantitative modeling of the contributions of localized surface plasmon resonance (LSPR) and interband transitions to absorbance
of gold nanoparticles has been achieved based on Lorentz–Drude dispersion function and Maxwell-Garnett effective medium approximation.
The contributions are well modeled with three Lorentz oscillators. Influence of the structural properties of the gold nanoparticles
on the LSPR and interband transitions has been examined. In addition, the dielectric function of the gold nanoparticles has
been extracted from the modeling to absorbance, and it is found to be consistent with the result yielded from the spectroscopic
ellipsometric analysis. 相似文献
2.
Nader Daneshfar Khashayar Bazyari 《Applied Physics A: Materials Science & Processing》2014,116(2):611-620
This theoretical work presents a comparative study of the optical properties and spectral tunability of hybrid multilayer spherical and cylindrical nanoshells based on the quasi-static approximation of classical electrodynamics. The interband transitions have been considered using the Drude–Lorentz model for the complex dielectric function of metallic layers because the optical properties of metals arise from both the optical excitation of interband transitions and the free-electron response. A general formula for N-ayer concentric nanoshells is arranged, and numerical calculations are performed for the four-layer nanoshells as an example. We have analyzed in detail different configurations of nanoshells such as dielectric-metal-dielectric-metal with dielectric core, metal-dielectric-metal-dielectric with metal core and semiconductor-metal-dielectric-metal with semiconductor core because composition of nanoshells have dramatic influence on their optical properties. The absorbance spectrum behavior of the shell thicknesses, surrounding medium, shape and composition of each layer of the nanoshell is numerically investigated. 相似文献
3.
J. Humli
ek J. Kircher H. -U. Habermeier M. Cardona 《Physica C: Superconductivity and its Applications》1992,190(4):383-395
Ellipsometry was used to study (110) and (001) oriented films of YBa2Cu3O7 and PrBa2Cu3O7 in the mid-and near-infrared spectral regions. Below a photon energy of 0.1 eV, the in-plane component of the dielectric tensor of YBa2Cu3O7 is dominated by a Drude term with a squared plasma energy of (3.0 ± 0.3) eV2. This “oscillator strength”, and the Lorentzian broadening energy of (0.104 ± 0.005) eV at room temperature, are confirmed by the changes induced in Pr-substituted material, and by low-temperature measurements in the near-infrared. The deviation from the Drude behavior observed above 0.1 eV is accounted for by a broad absorption band with an oscillator strength of (3.6 ± 0.1) eV2 in YBa2Cu3O7 which shifts to higher energies and takes over almost all of the oscillator strength of the Drude term when Y is substituted by Pr. The response to electric fields perpendicular to the planes is much weaker, with an upper bound of 0.63 eV2 for the squared plasma energy. The in-plane loss function computed from the measured dielectric function follows the Drude-like lineshape, modified by the bound-state absorption band, down to the lowest energy reached in our measurements (0.058 eV). 相似文献
4.
W. Lu P. L. Liu S. C. Shen M. von Ortenberg 《International Journal of Infrared and Millimeter Waves》1994,15(6):991-999
A general analytical expression is reported for the Drude model's dielectric function of free carrier in multi-valley IV-VI compound semiconductor in the magnetic field. The modifications of the energy band non-parabolicity and free carrier re-population are introduced to the dielectric function in combination with the
model. The difference of the dielectric function between the modified Drude model and the classical Drude model is demonstrated by the calculation for the typical IV-VI compound semiconductor material PbTe.Hai Da Fellow 相似文献
5.
Kociak M Stéphan O Henrard L Charbois V Rothschild A Tenne R Colliex C 《Physical review letters》2001,87(7):075501
We report on the investigation of surface-plasmon excitation of anisotropic WS(2) hollow nanoparticles in a near-field geometry by means of a scanning transmission electron microscope. The shell thickness influence on the electron-energy-loss-spectroscopy spectra is experimentally observed and is analyzed within a classical dielectric formalism. As for the isotropic case, we evidence one symmetric (tangential) and one antisymmetric (radial) mode. We point out the intriguing fact that, for the anisotropic case, one can relate these modes to the interband transition of the in-plane component of the dielectric tensor and to the bulk-plasmon energy of the out-of-plane component. 相似文献
6.
The contribution of interband transitions to the optical absorption of Cs colloids in a CsBr crystal has been calculated by introducing the expression of Wilson and Butcher for the imaginary part of the dielectric constant of cesium into the standard Mie theory. The resulting absorption bands are smaller and much broader than those corresponding to the free-electron model. The dependence of the calculated band half-width on colloid radius is compared with experimental data. The agreement obtained is considerably better than that corresponding to the sole Drude contribution 相似文献
7.
E. V. Golosov A. A. Ionin Yu. R. Kolobov S. I. Kudryashov A. E. Ligachev Yu. N. Novoselov L. V. Seleznev D. V. Sinitsyn 《Journal of Experimental and Theoretical Physics》2011,113(1):14-26
One-dimensional quasi-periodic nanogratings with spacings in the range from 160 to 600 nm are written on a dry or wet titanium
surface exposed to linearly polarized femtosecond IR and UV laser pulses with different surface energy densities. The topological
properties of the obtained surface nanostructures are studied by scanning electron microscopy. Despite the observation of
many harmonics of the one-dimensional surface relief in its Fourier spectra, a weak decreasing dependence of the first-harmonic
wavenumber (nanograting spacing) on the laser fluence is found. Studies of the instantaneous optical characteristics of the
material during laser irradiation by measuring the reflection of laser pump pulses and their simulation based on the Drude
model taking into account the dominant interband absorption allowed us to estimate the length of the excited surface electromagnetic
(plasmon-polariton) wave for different excitation conditions. This wavelength is quantitatively consistent with the corresponding
nanograting spacings of the first harmonic of the relief of the dry and wet titanium surfaces. It is shown that the dependence
of the first-harmonic nanograting spacing on the laser fluence is determined by a change in the instantaneous optical characteristics
of the material and the saturation of the interband absorption along with the increasing role of intraband transitions. Three
new methods are proposed for writing separate subwave surface nanogratings or their sets by femtosecond laser pulses using
the near-threshold nanostructuring, the forced adjustment of the optical characteristics of the material or selecting the
spectral range of laser radiation, and also by selecting an adjacent dielectric. 相似文献
8.
为了研究接触介质对金属光学性质的影响,实验中使用具有不同折射率的梯形棱镜作为衬底,将金和银蒸发到棱镜底部,用椭偏术分别测量了薄膜在金属-空气、金属-衬底界面的介电函数.结果表明:无论在Drude区,还是在带间跃迁区,金属-衬底界面处薄膜介电函数不仅与金属-空气界面处的测量值不同,而且随衬底折射率改变而改变.在固体接触条件下获得的结果与其他作者在液体接触条件下获得的结果相一致,但尚难被现有机制所解释.
关键词: 相似文献
9.
We introduce an analysis model, an extended Drude–Lorentz model, and apply it to Fe-pnictide systems to extract their electron–boson spectral density functions (or correlation spectra). The extended Drude–Lorentz model consists of an extended Drude mode for describing correlated charge carriers and Lorentz modes for interband transitions. The extended Drude mode can be obtained by a reverse process starting from the electron–boson spectral density function and extending to the optical self-energy and, eventually, to the optical conductivity. Using the extended Drude–Lorentz model, we obtained the electron–boson spectral density functions of K-doped BaFe2As2 (Ba-122) at four different doping levels. We discuss the doping-dependent properties of the electron–boson spectral density function of K-doped Ba-122. We also can include pseudogap effects in the model using this approach. Therefore, this approach is very helpful for understanding and analyzing measured optical spectra of strongly correlated electron systems, including high-temperature superconductors (cuprates and Fe-pnictides). 相似文献
10.
H. Keiter M. Rosenberg 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):599-603
The scale of relaxation times in glasses has led to generalizations of the Drude model of the dielectric function in terms
of an integral, containing a Drude kernel and a probability distribution. This integral equation is solved by a Mellin or
a Stieltjes transform. Beyond known results, we obtain the probability distribution of the Havriliak-Negami dielectric function.
Even more general classes of dielectric models can be dealt with, using Mellin's transform. They may serve as checks for numerical
procedures applied to the underlying ill-posed problem, if experimental data for the dielectric function are used.
Received: 2 February 1998 / Accepted: 17 March 1998 相似文献
11.
Silver films were deposited on glass substrates under different deposition conditions, i.e. different film thicknesses, deposition rates and deposition angles. Their optical properties were measured by spectrophotometry in the spectral range of 185–3300 nm. The Kramers–Kronig method was used to analyze the reflectivity curves of the silver films to obtain their optical constants. The influence of substrate temperature on the microstructure of thin metallic films, the structure zone model (SZM), is well established, whereas there has been some previous work on the influence of film thickness and morphology, deposition rate and deposition angle on the microstructure and morphology of thin films. An effective medium approximation (EMA) analysis was used to establish the relationship between the atomic force microscopy results, SZM predictions and EMA results, and hence the optical properties of silver thin films. The predictions of the Drude free-electron theory are compared with experimental results for dielectric functions of Ag films produced under different deposition conditions. The real part of the dielectric constant increases with film thickness and decreases with increasing deposition rate and with increasing incidence angle, whereas the imaginary part of the dielectric constant decreases with increasing film thickness and deposition rate and with decreasing incidence angle over the whole energy range measured, including the interaband and interband regions. 相似文献
12.
The dielectric properties of nanostructured wurtzite-type ZnO are studied by analyzing the low-loss region of the electron energy loss spectroscopy (EELS) in a transmission electron microscope. Characteristic peaks at about 12 and 32 eV in the imaginary part of the dielectric function shift to lower energies as particle size decreases. A comparison of experimental EELS spectra and ab initio density-functional theory calculations (WIEN2k code) within the generalized gradient approximation (GGA), GGA+U and modified Becke-Johnson (mBJ) is presented. The origins of interband transitions are identified in the electronic band structure by calculating the partial imaginary part of the dielectric function and the partial density of states of Zn and O. 相似文献
13.
We present measurements of the optical spectra on Na(0.7)CoO(2) single crystals. The optical conductivity shows two broad interband transition peaks at 1.6 eV and 3.1 eV, and a weak midinfrared peak at 0.4 eV. The intraband response of conducting carriers is different from that of a simple Drude metal. A peak at low but finite frequency is observed, which shifts to higher frequencies with increasing temperature, even though the dc resistivity is metallic. The origin of the interband transitions and the low-frequency charge dynamics have been discussed and compared with other experiments. 相似文献
14.
Energies and wave functions obtained from a recent band calculation are used in a computation of the interband optical conductivity of aluminum. The results are combined with a Drude term and compared with experiment. 相似文献
15.
J. Lermé B. Palpant B. Prével E. Cottancin M. Pellarin M. Treilleux J.L. Vialle A. Perez M. Broyer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(1):95-108
The optical response of free and matrix-embedded gold metal clusters AuN is investigated in the framework of the time-dependent local-density-approximation (TDLDA). The characteristics of the surface
plasmon resonance are carefully analyzed as a function of the model parameters and the particle radius. The strong influence
of the frequency-dependence of the 5d core-electron dielectric function in the vicinity of the interband threshold is emphasized. The size evolution of the Mie-frequency
in free gold clusters exhibits a noticeable blue-shift trend as the particle size decreases, much stronger than in silver
clusters. The width and shape of the resonance, essentially ruled by the decay via the interband transitions, are found closely correlated to the imaginary component of the core-electron dielectric function.
In presence of a surrounding matrix the blue-shift trend is largely rubbed out. Agreement with recent experimental results
on size-selected gold clusters embedded in an alumina matrix may be achieved by taking into account the porosity effects at
the metal/matrix interface. The comparison with the predictions of classical models is also provided.
Received: 9 March 1998 / Revised: 5 June 1998 / Accepted: 3 July 1998 相似文献
16.
The dynamical Casimir-Polder force between a neutral atom (in the ground state) and a thick plate in relativistic motion of
the atom in the direction parallel to the surface has been calculated. The material properties have been considered in the
framework of the oscillator model of the atom and the Drude dielectric function for a plate. The limiting cases of the nonrelativistic
velocity and perfectly conducting material of the plate have been discussed. A complex dependence of the force on the velocity
(energy), the distance, and the material properties of the surface has been found. 相似文献
17.
A solution to coupled wave equations, which describes the kinetics of nonsteady-state energy transfer between two light pulses
in a bulk medium with a local nonlinear response, has been obtained in the preset pump-field approximation. It is shown that
in a general case the energy transfer is an alternating function of the time delay between pulses, which is dominated by the
relative magnitude of the amplitude and phase components of the nonlinear response. The solution obtained was fitted to the
results of model experiments on Si. Agreement is reached with the fitting parameters determined from Drude theory for plasma-induced
variation of dielectric permittivity.
Fiz. Tverd. Tela (St. Petersburg) 39, 1980–1984 (November 1997) 相似文献
18.
《Journal of Electron Spectroscopy and Related Phenomena》2005,142(2):97-103
A new pair of Kramers–Kronig (KK) dispersion relationships for the transformation of surface energy loss function Im[−1/(ɛ + 1)] has been proposed. The validity of the new surface KK transform is confirmed, using both a Lorentz oscillator model and the surface energy loss functions determined from the experimental complex dielectric function of SrTiO3 and tungsten metal. The interband transition strength spectra (Jcv) have been derived either directly from the original complex dielectric function or from the derived dielectric function obtained from the KK transform of the surface energy loss function. The original Jcv trace and post-Jcv trace overlapped together for the three modes, indicating that the new surface Kramers–Kronig dispersion relationship is valid for the surface energy loss function. 相似文献
19.
The complex refractive indices and the dielectric function of GaN for frequencies ranging from 0.25 to 1.22THz are obtained using THz time-domain spectroscopy. The real part of the dielectric function first decreases from 0.25 to 0.42THz and then oscillates from 0.42 to 1.22THz, whereas the imaginary part of the dielectric function is oscillating within the whole range of frequency. The simple Drude model is extended to take into account the effect of defects on the dielectric function. The extended model is in agreement with the experimental data. 相似文献
20.
We study the influence of dielectric function of metals on the transmission properties of terahertz pulses through periodically patterned subwavelength holes. Because of a drastic increase in the value of dielectric constants, most metals become highly conductive at terahertz frequencies. Extraordinary terahertz transmission is observed in subwavelength hole arrays made from both good and poor electrical conductors. The measured transmittance of terahertz pulses is found to be enhanced with increasing ratio of the real to the imaginary dielectric constant of the constituent metals, for which the dielectric function follows the Drude model. 相似文献