Study of the Raman spectra of phonons in disordered GaSb/AlSb (001) superlattices

2010 ◽  
Vol 88 (9) ◽  
pp. 645-650 ◽  
Author(s):  
D. Berdekas
Keyword(s):  
Shell Model ◽  
Raman Spectra ◽  
Brillouin Zone ◽  
Dynamical Matrix ◽  
Phonon Spectra ◽  
Bond Polarizability ◽  
Lattice Planes

In the present work, we study the influence of disorder in the Raman spectra of the phonons of (GaSb)n/(AlSb)n (001) superlattices (SLs), for n = 1, 2. Τhe disordered superlattices are approximated with primitive cells that are much larger than the primitive cells of the corresponding perfect SLs. We propose that disorder appears because of deviations from the sequence of the GaSb and AlSb layers, which is imposed by symmetry, or because of intermixing of Ga and Al in the cation lattice planes. The dynamical matrix of each SL is constructed from the combination of the dynamical matrices of the bulk crystalline constituents, which have been calculated at certain points of the Brillouin zone with a ten-parameter valence overlap shell model. Further, we have calculated the Raman spectra of the disordered 1 × 1 and 2 × 2 superlattices grown along the (001) direction, using an eight-parameter bond polarizability model, away from resonance conditions. Our results show that intermixing of Ga and Al cations produce Raman activity that is not present in the phonon spectra of perfect superlattices.

scholarly journals Graphene Domain Signature of Raman Spectra of sp2 Amorphous Carbons

Nanomaterials ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 2021
Author(s):  
Elena F. Sheka ◽  
Yevgeny A. Golubev ◽  
Nadezhda A. Popova
Keyword(s):  
Raman Spectra ◽  
Molecular Spectroscopy ◽  
Basic Structure ◽  
Quasi Particle ◽  
Phonon Spectra ◽  
2D Pattern ◽  
Density Delocalization ◽  
Electron Density Delocalization ◽  
High Degree

The standard D-G-2D pattern of Raman spectra of sp2 amorphous carbons is considered from the viewpoint of graphene domains presenting their basic structure units (BSUs) in terms of molecular spectroscopy. The molecular approximation allows connecting the characteristic D-G doublet spectra image of one-phonon spectra with a considerable dispersion of the C=C bond lengths within graphene domains, governed by size, heteroatom necklace of BSUs as well as BSUs packing. The interpretation of 2D two-phonon spectra reveals a particular role of electrical anharmonicity in the spectra formation and attributes this effect to a high degree of the electron density delocalization in graphene domains. A size-stimulated transition from molecular to quasi-particle phonon consideration of Raman spectra was experimentally traced, which allowed evaluation of a free path of optical phonons in graphene crystal.

scholarly journals Symmetrical Analysis Phonon Modes of Crystal -Ag8SnSe6

2015 ◽  
Vol 16 (2) ◽  
pp. 257-260
Author(s):  
І.V. Semkiv ◽  
А.І. Kashuba ◽  
H.A. Ilchuk ◽  
M.V. Chekaylo
Keyword(s):  
Raman Spectra ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Group Symmetry ◽  
Phonon Modes ◽  
Orthorhombic System ◽  
Space Group Symmetry ◽  
Space Group ◽  
Phonon Spectra

Symmetrical analysis of the phonon spectra of  lowtemperature b¢-phase of crystal Ag8SnSe6 carried out. At the room temperature argyrodite Ag8SnSe6 belong to orthorhombic system with space group symmetry Pmn21. Classification of the main phonon modes of crystal carried out. Clarified selection rules for Raman spectra and infrared spectra.

New Developments in Raman Spectroscopy with Lasers: Electronic Transitions

1968 ◽  
Vol 22 (5) ◽  
pp. 438-444 ◽  
Author(s):  
J. A. Koningstein
Keyword(s):  
Raman Spectroscopy ◽  
Single Crystals ◽  
Crystal Field ◽  
Raman Spectra ◽  
Raman Effect ◽  
Electronic Transitions ◽  
New Developments ◽  
Selection Rules ◽  
Phonon Spectra ◽  
Host Lattices

A discussion is given of the Raman spectra of single crystals of yttrium gallium garnet (YGaG), of ytterbrium gallium garnet (YbGaG), and of Yb:YGaG. From a comparison of the spectra it has been possible to separate the phonon spectra of the host lattices from that of an electronic Raman effect which occurs between the crystal field levels of the 2F7/2 manifold of Yb3+ in the garnet crystals. Information with respect to the selection rules governing both types of spectra is given.

scholarly journals C60 Filling Rate in Carbon Peapods: A Nonresonant Raman Spectra Analysis

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Fatima Fergani ◽  
Sidi Abdelmajid Ait Abdelkader ◽  
Hassane Chadli ◽  
Brahim Fakrach ◽  
Abdelhai Rahmani ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Experimental Method ◽  
Raman Spectra ◽  
Double Helix ◽  
Single Walled Carbon Nanotubes ◽  
Filling Rate ◽  
Spectra Analysis ◽  
Single Walled Carbon ◽  
Bond Polarizability ◽  
Walled Carbon Nanotubes

We calculated the nonresonant Raman spectra of C60 peapods to determine the concentration of C60 fullerenes inside single-walled carbon nanotubes. We focus on peapods with large diameters for which C60 molecules can adopt a double helix configuration or a two-molecule layer configuration. Our calculations are performed within the framework of the bond-polarizability model combined with the spectral moment’s method. The changes in the Raman spectra as a function of C60 filling rate and the configuration of C60 molecules inside the nanotubes are identified and discussed. Our calculations support the experimental method proposed by Kuzmany to evaluate the concentration of C60 molecules inside nanotubes.

Phonon Dispersion in ZnSe

1972 ◽  
Vol 50 (21) ◽  
pp. 2596-2604 ◽  
Author(s):  
J. C. Irwin ◽  
J. LaCombe
Keyword(s):  
Experimental Data ◽  
Theoretical Model ◽  
Specific Heat ◽  
Single Crystals ◽  
Raman Spectra ◽  
Density Of States ◽  
Brillouin Zone ◽  
Critical Points ◽  
Phonon Dispersion ◽  
Zone Boundary

Second-order Raman spectra have been obtained from oriented single crystals of ZnSe. The spectra have been interpreted and the results have been used to determine the zone boundary frequencies at the critical points X, L, and W. The resulting set of frequencies are consistent with known polarization selection rules and with a theoretical model. The frequencies in turn serve to determine the parameters in the theoretical model and the resulting model has been used to calculate the phonon dispersion throughout the Brillouin zone, the density of states, and the specific heat. The results are compared to the small amount of experimental data that is available.

Impurity-induced Raman spectra of CsBr:Tl+: A breathing-shell-model calculation

1977 ◽  
Vol 16 (12) ◽  
pp. 5585-5591 ◽  
Author(s):  
M. S. Haque ◽  
D. Strauch ◽  
H. Krause ◽  
T. Suski
Keyword(s):  
Shell Model ◽  
Model Calculation ◽  
Raman Spectra ◽  
Shell Model Calculation

Interface Effects on the Raman Spectra of Si/3C-SiC Superlattices

2000 ◽  
Vol 640 ◽  
Author(s):  
E. F. Bezerra ◽  
A. G. Souza Filho ◽  
J. Mendes Filho ◽  
V. Lemos ◽  
V. N. Freire ◽  
...  
Keyword(s):  
Raman Spectra ◽  
Theoretical Calculations ◽  
Linear Chain ◽  
Dispersion Relations ◽  
Chain Model ◽  
Virtual Crystal Approximation ◽  
Smooth Interface ◽  
Bond Polarizability ◽  
Interface Effects

ABSTRACTTheoretical calculations are performed on the role of smooth interfaces in the Raman spectra of Si/3C-SiC superlattices. The dispersion relations were obtained using a linear chain model with the alloyed interface δ-(3C-SiC)0.5(Si)0.5 described in the virtual crystal approximation. A modified bond-polarizability model was used to calculate the Raman spectra. The main results are the enhancement of the Raman spectra and the appearance of new peaks in between those related to the Si quasi confined and the 3C-SiC-confined modes with increasing number δ?of interfacial monolayers (3C-SiC)0.5(Si)0.5. Some of the smooth interface related Raman peaks have intensity comparable with those of an abrupt Si/3C-SiC superlattice.

Second-Order Raman Spectra of Fluorites. I. Critical Point Analysis

1972 ◽  
Vol 50 (8) ◽  
pp. 849-857 ◽  
Author(s):  
N. Krishnamurthy ◽  
V. Soots
Keyword(s):  
Critical Point ◽  
Single Crystals ◽  
Raman Spectra ◽  
Brillouin Zone ◽  
Critical Points ◽  
Photon Counting ◽  
Second Order ◽  
Selection Rules ◽  
Point Analysis ◽  
Critical Point Analysis

With the use of a high-powered Ar+ laser and conventional photon counting techniques it has been possible to observe the second-order Raman spectra of single crystals of CaF2, SrF2, BaF2, and PbF2. The symmetries of the various parts of the spectra of the latter two were determined by using oriented single crystals of these two fluorides. The main features of the observed spectra have been analyzed, with the aid of group-theoretical selection rules, in terms of calculated phonon frequencies at the critical points of the Brillouin zone of these crystals.

scholarly journals Lattice Dynamical Study of Platinum by Use of van der Waals Three Body Force Shell Model

2020 ◽  
Author(s):  
U C Srivastava
Keyword(s):  
Shell Model ◽  
Body Force ◽  
Present Model ◽  
Van Der Waals ◽  
Dynamical Study ◽  
Stiffness Constant ◽  
Phonon Spectra ◽  
Three Body ◽  
Rigid Shell ◽  
Fcc Structure

In present article author considered the lattice dynamical study of platinum by use of van der Waals three body force shell model [VTBFSM] due to high stiffness constant C11 and C12 . The present model uses with the frequencies of the optical and vibrational branches in the direction [100] and phonon density of states.The study of phonon spectra are important in determining the mechanica1, electrical and thermodynamical properties of elements and their alloys. The present model incorporates the effect of (VWI) and (TBI) into the rigid shell model with fcc structure, operative up to the second neighbors in short range interactions. The available measured data for platinum (Pt) well agrees with our results.

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