scholarly journals Anisotropy and phonon modes from analysis of the dielectric function tensor and the inverse dielectric function tensor of monoclinic yttrium orthosilicate

2018 ◽  
Vol 97 (16) ◽  
Author(s):  
A. Mock ◽  
R. Korlacki ◽  
S. Knight ◽  
M. Schubert
Keyword(s):  
Dielectric Function ◽  
Phonon Modes

Far-infrared dielectric function and phonon modes of spontaneously ordered (AlxGa1−x)0.52In0.48P

2004 ◽  
Vol 455-456 ◽  
pp. 601-604 ◽  
Author(s):  
Tino Hofmann ◽  
Mathias Schubert ◽  
Volker Gottschalch
Keyword(s):  
Dielectric Function ◽  
Far Infrared ◽  
Phonon Modes

Infrared dielectric function and phonon modes of highly disordered(AlxGa1−x)0.52In0.48P

2001 ◽  
Vol 64 (15) ◽  
Author(s):  
T. Hofmann ◽  
G. Leibiger ◽  
V. Gottschalch ◽  
Ines Pietzonka ◽  
M. Schubert
Keyword(s):  
Dielectric Function ◽  
Phonon Modes

Optical Constants, Critical Points, and Phonon Modes of GaAsN Single Layers

2000 ◽  
Vol 639 ◽  
Author(s):  
G. Leibiger ◽  
V. Gottschalch ◽  
A. Kasik ◽  
B. Rheinländer ◽  
J. Šik ◽  
...  
Keyword(s):  
Band Gap ◽  
Dielectric Function ◽  
Critical Points ◽  
Optical Constants ◽  
Blue Shift ◽  
Band Gap Energy ◽  
Phonon Modes ◽  
Transition Energies ◽  
Infrared Spectral Range ◽  
Infrared Spectral

ABSTRACTSpectroscopic ellipsometry (SE) is employed to study the optical properties of GaAs1−yNy [0% ≤ y ≤ 3.7%] single layers for photon energies from 0.75 eV to 4.5 eV and for wavenumbers from 100 cm−1 to 600 cm−1. We provide parametric model functions for the dielectric function spectra of GaAsN in both photon energy ranges. The model functions for photon energies from 0.75 eV to 4.5 eV excellently match dielectric function data obtained from a numerical wavelength-by-wavelength inversion of the experimental data. Criticalpoint analysis of the ellipsometric data is performed in the spectral regions of the fundamental band gap and the critical points E1 and E1+δ1. The band-gap energy is red shifted whereas the E1 and E1+δ1 transition energies are blue shifted with increasing y. For y ≤ 1.65% the observed blue shift of the E1 energy is well explained by the sum of the effects of biaxial (001) strain and alloying. The GaAsN layers show two-mode behaviour in the infrared spectral range (100 cm−1 to 600 cm−1). We detect the transverse GaAs- and GaN- sublattice modes at wavenumbers of about 267 cm−1 and 470 cm−1, respectively. The polar strength of the GaN TO mode increases linearly with y. This effect can be used to monitor the nitrogen composition in GaAsN layers.

Infrared dielectric function and phonon modes of Mg-rich cubic MgxZn1−xO(x⩾0.67) thin films on sapphire (0001)

2004 ◽  
Vol 85 (6) ◽  
pp. 905-907 ◽  
Author(s):  
C. Bundesmann ◽  
M. Schubert ◽  
A. Rahm ◽  
D. Spemann ◽  
H. Hochmuth ◽  
...  
Keyword(s):  
Thin Films ◽  
Dielectric Function ◽  
Phonon Modes

Coupled plasmon-LO phonon modes and Lindhard-Mermin dielectric function of n-GaAs

1979 ◽  
Vol 30 (11) ◽  
pp. 703-707 ◽  
Author(s):  
G. Abstreiter ◽  
R. Trommer ◽  
M. Cardona ◽  
A. Pinczuk
Keyword(s):  
Dielectric Function ◽  
Phonon Modes

Radiative Properties of GaAs From First Principles Calculations

2008 ◽  
Author(s):  
Hua Bao ◽  
Xiulin Ruan
Keyword(s):  
Band Structure ◽  
Dielectric Function ◽  
First Principles ◽  
Electronic Band Structure ◽  
Golden Rule ◽  
Radiative Properties ◽  
Initial Structure ◽  
Phonon Modes ◽  
Electronic Band ◽  
Near Ir

Spectral reflectance of GaAs from infrared (IR) to ultra-violet (UV) bands is calculated from first principles. We first calculate the spectral dielectric function which is determined by the response of GaAs to external electromagnetic field. Two mechanisms exist for different wavelengths, namely, phonon absorption in the far-IR region and the electronic absorption in the near-IR to UV region. With plane-wave pseudopotential method, we determined the dielectric function of GaAs with the the initial structure as the only input. For the far-IR region, phonon calculations are carried out. By analyzing the phonon modes, low-frequency dielectric constant is calculated. For the near-IR to UV band, the electronic band structure of GaAs is calculated, and the imaginary part of the dielectric function is determined from the band structure using Fermi’s Golden rule. The real part of spectral dielectric function is then derived from Kramer-Kronig transformation. The reflectance is then calculated using Maxwell’s equations.

Optical properties of the Vanadium dioxide

2015 ◽  
Vol 8 (2) ◽  
pp. 2148-2155 ◽  
Author(s):  
Abderrahim Benchaib ◽  
Abdesselam Mdaa ◽  
Izeddine Zorkani ◽  
Anouar Jorio
Keyword(s):  
Energy Efficiency ◽  
Optical Properties ◽  
Critical Temperature ◽  
Thin Layer ◽  
Dielectric Function ◽  
Vanadium Dioxide ◽  
Ultra Violet ◽  
Index Of Refraction ◽  
Practical Utility ◽  
Infra Red

The vanadium dioxide is a material thermo chromium which sees its optical properties changing at the time of the transition from the phase of semiconductor state ↔ metal, at a critical temperature of 68°C. The study of the optical properties of a thin layer of VO₂ thickness 82 nm, such as the dielectric function, the index of refraction, the coefficient ofextinction, the absorption’s coefficient, the reflectivity, the transmittivity, in the photonic spectrum of energy ω located inthe interval: 0.001242 ≤ ω (ev) ≤ 6, enables us to control well its practical utility in various applications, like the intelligentpanes, the photovoltaic, paintings for increasing energy efficiency in buildings, detectors of infra-red (I.R) or ultra-violet(U.V). We will make simulations with Maple and compare our results with those of the literature

From Semiconductor to Metal in a Flash: Observing Ultrafast Laser-Induced Phase Transformations

1997 ◽  
Vol 481 ◽  
Author(s):  
J. P. Callan ◽  
A. M.-T. Kim ◽  
L. Huangt ◽  
E. N. Glezer ◽  
E. Mazur
Keyword(s):  
Phase Transformations ◽  
Dielectric Function ◽  
Spectral Range ◽  
Laser Excitation ◽  
Spectroscopic Technique ◽  
Ultrafast Laser ◽  
Lattice Heating ◽  
Fs Laser

ABSTRACTWe use a new broadband spectroscopic technique to measure ultrafast changes in the dielectric function of a material over the spectral range 1.5–3.5 eV following intense 70-fs laser excitation. The results reveal the nature of the phase transformations which occur in the material following excitation. We studied the response of GaAs and Si. For GaAs, there are three distinct regimes of behavior as the pump fluence is increased — lattice heating, lattice disordering, and a semiconductor-to-metal transition.

scholarly journals Phonons in Short-Period GaN/AlN Superlattices: Group-Theoretical Analysis, Ab initio Calculations, and Raman Spectra

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 286
Author(s):  
Valery Davydov ◽  
Evgenii Roginskii ◽  
Yuri Kitaev ◽  
Alexander Smirnov ◽  
Ilya Eliseyev ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Raman Spectra ◽  
Density Functional ◽  
Structural Characteristics ◽  
Vibrational Modes ◽  
Phonon Modes ◽  
Short Period ◽  
Group Theoretical Analysis

We report the results of experimental and theoretical studies of phonon modes in GaN/AlN superlattices (SLs) with a period of several atomic layers, grown by submonolayer digital plasma-assisted molecular-beam epitaxy, which have a great potential for use in quantum and stress engineering. Using detailed group-theoretical analysis, the genesis of the SL vibrational modes from the modes of bulk AlN and GaN crystals is established. Ab initio calculations in the framework of the density functional theory, aimed at studying the phonon states, are performed for SLs with both equal and unequal layer thicknesses. The frequencies of the vibrational modes are calculated, and atomic displacement patterns are obtained. Raman spectra are calculated and compared with the experimental ones. The results of the ab initio calculations are in good agreement with the experimental Raman spectra and the results of the group-theoretical analysis. As a result of comprehensive studies, the correlations between the parameters of acoustic and optical phonons and the structure of SLs are obtained. This opens up new possibilities for the analysis of the structural characteristics of short-period GaN/AlN SLs using Raman spectroscopy. The results obtained can be used to optimize the growth technologies aimed to form structurally perfect short-period GaN/AlN SLs.

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