2024 |
Raseev, G. (2024). Optical intensity figures of merit of insulator-metal-insulator and metal-insulator-metal thin-film stacks. Phys. Scr., 99, 085535.
Résumé: Figures of merit (FoM) are used to characterise the mode intensity and leakage of reflection and plane-wave and locally excited transmitted fluxes of simple insulator-metal-insulator (IMI) and metal-insulator-metal (MIM) 2D planar thin-film stacks sustaining a single surface plasmon polariton (SPP) and multiple planar waveguide (PWG) modes. This first comparative study of the intensity FoM (IFoM) of IMI and MIM stack modes is carried out by analysing these observables 3D dispersion graph (observable dispersion/in-plane wave vector/frequency) along 2D cuts where one of the independent variables is fixed. In the spatial domain, the observable 2D dispersion curves along the in-plane wave vector at a given frequency are examined. In the frequency domain, these 2D dispersion curves are examined along the frequency at a given in-plane wave vector. Due to the lower leakage, the quality factors and IFoM of the IMI and MIM thin film stack modes are significantly larger in the spatial domain than in the frequency domain. Our optimized quality factors and IFoMs can be larger than those obtained in some 2D/3D nanoscale samples with an involved geometry.
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2013 |
Raseev, G. (2013). Plasmon resonances of Ag(001) and Ag(111) studied by power density absorption and photoyield. Surf. Sci., 615, 6–20.
Résumé: This paper models the surface and bulk plasmon resonances in photoabsorption and photoelectron spectra (PES) of the Ag(001) and the Ag(111) surfaces in the region of 2.8-10 eV excited with a p or transverse magnetic linearly polarized laser incident at 45 degrees. Using the recently developed vector potential from electron density-coupled integro-differential equations (VPED-CIDE, [1,2]) model, we calculate the electron escaping probability from the power density absorption, Feibelman's parameter d(perpendicular to), the reflectance and the Fermi PE cross section. In the PES experiment the work function is lowered from 45 to 2.8 eV by adsorption of sodium. In our model, this lowering is introduced by adding a phenomenological term to the DFT-LDA model potential of Chulkov et al. [3]. For both Ag(001) and Ag(111), the calculated observables display two plasmon resonances, the multipole surface at 3.70 eV and the bulk at 3.90 eV, in fair agreement with the experimental PES of Barman et al. [4,5] and the reflectance. Except for the Fermi PE cross section of Ag(001) which does not display the multipole surface plasmon resonance at 3.70 eV. This poor result is probably due to a poor calculation of the conduction band wave functions obtained from the Schrodinger equation using the modified DFT-LDA model potential of Chulkov et at (C) 2013 Elsevier B.V. All rights reserved.
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2012 |
Raseev, G. (2012). Laser fields at flat interfaces: I. Vector potential. Eur. Phys. J. D, 66(7), 179.
Résumé: A model calculating the laser fields at a flat structureless surface taking into account the surface photoelectric effect is presented. The photon is p or transverse magnetic linearly polarized, continuous and its wave length is long, i.e. lambda(vac) >= 12.4 nm. The sharp rise of the electron density at the interface generates an atomic scale spatial dependence of the laser field. In real space and in the temporal gauge, the vector potential A of the laser is obtained as a solution of the classical Ampere-Maxwell and the material equations. The susceptibility is a product of the electron density of the material system with the surface and of the bulk tensor and non-local isotropic (TNLI) polarizability. The electron density is obtained quantum mechanically by solving the Schrodinger equation. The bulk TNLI polarizability including dispersion is calculated from a Drude-Lindhard-Kliewer model. In one dimension perpendicular to the surface the components A(x)(z,omega) and A(z)(z,omega) of the vector potential are solutions of the Ampere-Maxwell system of two coupled integro-differential equations. The model, called vector potential from the electron density-coupled integro-differential equations (VPED-CIDE), is used here to obtain the electron escape probability from the power density absorption, the reflectance, the electron density induced by the laser and Feibelman's parameters d(parallel to) and d(perpendicular to). Some preliminary results on aluminium surfaces are given here and in a companion paper the photoelectron spectra are calculated with results in agreement with the experiment.
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Raseev, G. (2012). Laser fields at flat interfaces: II. Plasmon resonances in aluminium photoelectron spectra. Eur. Phys. J. D, 66(7), 180.
Résumé: Using the model derived in paper I [G. Raseev, Eur. Phys. J. D 66, 167 (2012)], this work presents calculations of the photoelectron spectrum (PES) of low index aluminium surfaces in the 10-30 eV region. The laser is p or transverse magnetic linearly polarized incident on a flat structureless surface and its fields are modeled in I using the vector potential in the temporal gauge. This model uses a tensor and nonlocal isotropic (TNLI) susceptibility and solves the classical Ampere-Maxwell equation through the use of the vector potential from the electron density-coupled integro-differential equations (VPED-CIDE). The PE cross sections are the squares of the PE transition moments calculated using the VPED-CIDE vector potential function of the penetration coordinate. The PES is obtained in a one step model using either the Fermi golden rule or the Weisskopf-Wigner (WW) expressions. The WW cross section PES compares favorably with the experimental angle and energy resolved photoelectron yield (AERPY) spectrum of Levinson et al. [Phys. Rev. Lett. 43, 952 (1979)], Levinson and Plummer [Phys. Rev. B 24, 628 (1981)] for Al(001) and of Barman et al. [Phys. Rev. B 58, R4285 (1998)], Barman [Curr. Sci. 88, 54 (2005)] for Al(111) surfaces. As in the experiment, our theoretical AERPY displays the multipole surface plasmon resonance at 11.32/12.75 eV for Al(001)/Al(111), mainly due to the surface contribution vertical bar <psi(f)vertical bar p . A vertical bar psi(i)>vertical bar(2), the bulk plasmon minimum at 15 eV and the two single particle excitation resonances at about 16 and 22 eV. The nature of the plasmon resonances of the PES is analyzed using the reflectance, the electron density induced by the laser and Feibelman's parameter d(perpendicular to) all introduced in paper I.
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2010 |
Raseev, G., & Bejan, D. (2010). Multipole surface plasmon resonance of an aluminium surface. Opt. Commun., 283(20), 3976–3984.
Résumé: The surface photoelectric effect and the surface plasmon resonances appear when a p/transverse magnetic polarized laser hits a gas-solid interface. We model this effect in the long wave length (LWL) domain (lambda(vac)>10 nm, (h) over cap omega<124 eV) by combining the Ampere-Maxwell equation, written in classical approximation, with the material equation for the susceptibility. The resulting model, called the vector potential from the electron density (VPED), calculates the susceptibility as a product of the bulk susceptibility and the electron density of the actual system. The bulk susceptibility is a sum of the bound electron scalar susceptibility taken from the experiment and of the conduction electron non-local isotropic susceptibility tensor in a jellium metal (Lindhard, 1954 [1]). The electron density is the square of the wave function solution of the Schrodinger equation. The analysis of observables, the reflectance R and the photoelectron yield Y as well as the induced charge density permits to identify and characterize the multipole surface plasmon resonance of Al(111) appearing at omega(m) similar to 0.8 omega(p), or 11-12 eV. (c) 2010 Elsevier B.V. All rights reserved.
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