Identification of longitudinal optical modes by hyper-Raman scattering in noncentrosymmetric ceramics

2005 ◽  
Vol 87 (5) ◽  
pp. 051104 ◽  
Author(s):  
Holger Hellwig
Keyword(s):  
Raman Scattering ◽  
Longitudinal Optical ◽  
Optical Modes

Long-wavelength lattice vibrations of Ag3In5Se9 and Ag3In5Te9 single crystals — An inversion of LO- and TO-mode frequencies

2016 ◽  
Vol 30 (18) ◽  
pp. 1650229 ◽  
Author(s):  
Nizami Mamed Gasanly
Keyword(s):  
Refractive Index ◽  
Single Crystals ◽  
Longitudinal Optical ◽  
Absorption Index ◽  
Energy Losses ◽  
Optical Parameters ◽  
Lattice Vibrations ◽  
Frequency Range ◽  
Long Wavelength ◽  
Optical Modes

Infrared (IR) reflectivities are registered in the frequency range of 50–2000 cm[Formula: see text] for Ag3In5Se9 and Ag3In5Te9 single crystals grown by Bridgman method. Three infrared-active modes are detected in spectra. The optical parameters, real and imaginary parts of the dielectric function, the function of energy losses, refractive index, absorption index and absorption coefficient were calculated from reflectivity experiments. The frequencies of transverse and longitudinal optical modes (TO and LO modes) and oscillator strength were also determined. The bands detected in infrared spectra were tentatively attributed to various vibration types (valence and valence-deformation). The inversion of LO- and TO-mode frequencies of the sandwiched pair was observed for studied crystals.

scholarly journals On the dynamics of polarons in the strong-coupling limit

2017 ◽  
Vol 29 (10) ◽  
pp. 1750030 ◽  
Author(s):  
Marcel Griesemer
Keyword(s):  
Strong Coupling ◽  
Longitudinal Optical ◽  
Strong Coupling Limit ◽  
Poisson System ◽  
Phonon Modes ◽  
Polar Crystal ◽  
Effective Dynamics ◽  
Optical Modes ◽  
Non Local ◽  
With Memory

The polaron model of H. Fröhlich describes an electron coupled to the quantized longitudinal optical modes of a polar crystal. In the strong-coupling limit, one expects that the phonon modes may be treated classically, which leads to a coupled Schrödinger–Poisson system with memory. For the effective dynamics of the electron, this amounts to a nonlinear and non-local Schrödinger equation. We use the Dirac–Frenkel variational principle to derive the Schrödinger–Poisson system from the Fröhlich model and we present new results on the accuracy of their solutions for describing the motion of Fröhlich polarons in the strong-coupling limit. Our main result extends to [Formula: see text]-polaron systems.

Raman Scattering by Optical Modes of Metals

1969 ◽  
pp. 389-397 ◽  
Author(s):  
James H. Parker ◽  
D. W. Feldman ◽  
M. Ashkin
Keyword(s):  
Raman Scattering ◽  
Optical Modes

scholarly journals Structural and optical study of alternating layers of In and GaAs prepared by magnetron sputtering

2019 ◽  
Vol 24 (3) ◽  
pp. 523-542 ◽  
Author(s):  
Santiago Torres-Jaramillo ◽  
Camilo Pulzara-Mora ◽  
Roberto Bernal-Correa ◽  
Miguel Venegas de la Cerda ◽  
Salvador Gallardo-Hernández ◽  
...  
Keyword(s):  
Magnetron Sputtering ◽  
Low Cost ◽  
Longitudinal Mode ◽  
Longitudinal Optical ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mode Behavior ◽  
Optical Modes ◽  
High Concentrations ◽  
Secondary Ion

Currently, the obtention of nano-structures based on III-V materials is expensive. This calls for novel and inexpensive nanostructure manufacturing approaches. In this work we report on the manufacture of a nanostructures consisting of alternating layers of In and GaAs on a silicon substrate by magnetron sputtering. Furthermore, we characterized the produced nanostructures using secondary ion mass spectroscopy (SIMS), X-ray diffraction analysis, and Raman spectroscopy. SIMS revealed variation in the concentration of In atoms across In/GaAs/In interphases, and X-ray diffraction revealed planes corresponding to phases associated with GaAs and InAs due to In interfacial diffusion across GaAs layers. Finally, in order to study the composition and crystalquality of the manufactured nanostaructures, Raman spectra were taken using laser excitation lines of 452 nm, 532 nm, and 562 nm at different points across the nanostructures.This allowed to determine the transverse and longitudinal optical modes of GaAs and InAs,characteristic of a two-mode behavior. An acoustic longitudinal vibrational mode LA(Γ) of GaAs and an acoustic longitudinal mode activated by disorder (DALA) were observed. These resulted from the substitution of Ga atoms for In atoms in high concentrations due to the generation of Ga(VGa) and/or Arsenic(VAs) vacancies.This set of analyses show that magnetron sputtering can be aviable and relatively low-cost technique to obtain this type of semiconductors.

ONE-PHONON-ASSISTED ELECTRON RESONANT RAMAN SCATTERING IN FREE-STANDING QUANTUM WIRES

2007 ◽  
Vol 21 (17) ◽  
pp. 2989-3000
Author(s):  
XIANG-FU ZHAO ◽  
CUI-HONG LIU
Keyword(s):  
Raman Scattering ◽  
Quantum Wire ◽  
Quantum Wires ◽  
Longitudinal Optical ◽  
Phonon Modes ◽  
Free Standing ◽  
Surface Optical ◽  
Resonant Raman ◽  
Resonant Raman Scattering ◽  
Valence Bands

The scattering intensity (SI) for an electron resonant Raman scattering (ERRS) process in a free-standing semiconductor quantum wire of cylindrical geometry associated with bulk longitudinal optical (LO) phonon modes or the surface optical (SO) phonon modes is calculated for T=0 K . The Fröhlich interaction is considered to illustrate the theory for a GaAs system. Electron states are confined within a free-standing quantum wire (FSW). Single parabolic conduction and valence bands are assumed. The selection rules are studied. Numerical results and a discussion are also presented for various radii of the cylindrical quantum wires.

The Lifetime of Polar-Optical Modes in Semiconductors

2009 ◽  
Vol 1221 ◽  
Author(s):  
Brian K Ridley ◽  
Angela Dyson
Keyword(s):  
Raman Scattering ◽  
Bulk Material ◽  
Phonon Modes ◽  
High Frequencies ◽  
Power Semiconductor ◽  
Power Semiconductor Devices ◽  
Optical Modes ◽  
Electronic Performance ◽  
Anharmonic Decay

AbstractAn enduring problem in the engineering of high-power semiconductor devices is how to mitigate the effect of heating. Heating means the proliferation of phonons, and phonons, interacting with electrons directly affect the electronic performance of the device. Nowhere is this more evident than the role of hot polar-optical phonons in reducing the drift velocity in the channel of an HFET and hence reducing its performance at high frequencies. The task of describing hot-phonon effects is complicated by the coupling to plasma modes. We present a theory of coupled plasmon-phonon modes in GaN, how they interact with electrons and how their lifetime becomes density-dependent. Raman scattering in bulk material shows a reduction of lifetime with increasing density and we offer an explanation for this in terms of the frequency dependence of the anharmonic decay mechanism. Hot-phonon effects, however, involve modes with wave-vectors beyond those probed by Raman scattering. By adopting a single-pole approximation for these modes we have obtained the lifetime dependence on wave vector, electron temperature and density.

Raman scattering study of the long-wavelength longitudinal-optical-phonon–plasmon coupled modes in high-mobility InN layers

2009 ◽  
Vol 79 (15) ◽  
Author(s):  
Ramon Cuscó ◽  
Jordi Ibáñez ◽  
Esther Alarcón-Lladó ◽  
Luis Artús ◽  
Tomohiro Yamaguchi ◽  
...  
Keyword(s):  
Raman Scattering ◽  
Optical Phonon ◽  
High Mobility ◽  
Longitudinal Optical ◽  
Longitudinal Optical Phonon ◽  
Coupled Modes ◽  
Long Wavelength ◽  
Scattering Study
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