Showing papers on "Brillouin zone published in 1999"
TL;DR: In this article, the origin and dispersion of the anomalous disorder-induced Raman band (D$ band) observed in all hybridized disordered carbon materials near the K point of the Brillouin zone was investigated as a function of incident laser energy.
Abstract: The origin and dispersion of the anomalous disorder-induced Raman band $(D$ band) observed in all ${\mathrm{sp}}^{2}$ hybridized disordered carbon materials near 1350 ${\mathrm{cm}}^{\ensuremath{-}1}$ is investigated as a function of incident laser energy. This effect is explained in terms of the coupling between electrons and phonons with the same wave vector near the K point of the Brillouin zone. The high dispersion is ascribed to the coupling between the optic phonons associated with the D band and the transverse acoustic branch. The large Raman cross section is due to the breathing motion of these particular phonons near the K point. Our model challenges the idea that the Raman D peak is due to laser-energy-independent features in the phonon density of states, but rather is due to a resonant Raman process.
886 citations
TL;DR: In this article, the authors used the Monte Carlo method to simulate electron transport for electric field strengths up to 350 kV/cm in bulk, wurtzite structure ZnO.
Abstract: The Monte Carlo method is used to simulate electron transport for electric field strengths up to 350 kV/cm in bulk, wurtzite structure ZnO. The relevant parts of the conduction bands of a first-principles band structure are approximated by spherically symmetric, nonparabolic valleys located at the Γ and Umin symmetry points of the Brillouin zone. It is shown that the analytic expressions represent the band structure and the density of states well over a range of nearly 5 eV from the bottom of the conduction band. The simulated electron steady-state drift velocity versus electric field characteristics are calculated for lattice temperatures of 300, 450, and 600 K. For room temperature, drift velocities higher than 3×107 cm/s are reached at fields near 250 kV/cm. Examination of the electron energy distributions shows that the strong decrease of the differential mobility with increasing electric field in the field range studied is to be associated with the pronounced nonparabolicity of the central valley and...
170 citations
TL;DR: In this article, the angular dependent reflectivity spectra of semiconductor photonic crystals fabricated by deep periodic patterning of AlGaAs surface waveguides are studied by angular dependent reflection.
Abstract: Sharp resonance features are observed in the polarized reflectivity spectra of semiconductor photonic crystals fabricated by deep periodic patterning of AlGaAs surface waveguides. Both one- (1-D) and two-dimensional (2-D) lattices are studied by angular dependent reflectivity. By comparison with theory we show that the sharp features in reflectivity arise from resonant coupling of the external radiation to the folded band structure of the photonic crystal waveguides. Wavevector selective coupling to "heavy photon" states at the edge of the photonic Brillouin zone is demonstrated for the 1-D lattices. In the case of the 2-D lattices we observe polarization mixing of the photonic hands. Theoretical reflectivity spectra were obtained from a numerical solution of Maxwells equations for the patterned waveguide and were found to be in very good agreement with experiment.
164 citations
TL;DR: An experimental study of spin-wave quantization in arrays of micron-size magnetic wires by means of Brillouin light-scattering spectroscopy is reported in this paper, where Dipolar-dominated Damon-Eshbach spinwave modes laterally quantized in a single wire with quantized wave vector values determined by the width of the wire are studied.
Abstract: An experimental study of spin-wave quantization in arrays of micron-size magnetic ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ wires by means of Brillouin light-scattering spectroscopy is reported Dipolar-dominated Damon-Eshbach spin-wave modes laterally quantized in a single wire with quantized wave vector values determined by the width of the wire are studied The frequency splitting between quantized modes, which decreases with increasing mode number, depends on the wire sizes and is up to 15 GHz The transferred wave vector interval, where each mode is observed, is calculated using a light-scattering theory for confined geometries The frequencies of the modes are calculated, taking into account finite-size effects The results of the calculations are in a good agreement with the experimental data
157 citations
TL;DR: Angle-resolved photoemission spectroscopy was carried out on CuO(4), a model system of the charge- and spin-ordered state, or stripe phase, which provides important information for establishing a theory to understand the charge and spin ordering in cuprates and their relation with high-temperature superconductivity.
Abstract: Angle-resolved photoemission spectroscopy was carried out on (La1.28Nd0.6Sr0.12)CuO4, a model system of the charge- and spin-ordered state, or stripe phase. The electronic structure contains characteristic features consistent with other cuprates, such as the flat band at low energy near the Brillouin zone face. However, the low-energy excitation near the expected d -wave node region is strongly suppressed. The frequency-integrated spectral weight is confined inside one-dimensional segments in the momentum space (defined by horizontal momenta | kx | = π/4 and vertical momenta | ky | = π/4), deviating strongly from the more rounded Fermi surface expected from band calculations. This departure from the two-dimensional Fermi surface persists to a very high energy scale. These results provide important information for establishing a theory to understand the charge and spin ordering in cuprates and their relation with high-temperature superconductivity.
157 citations
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TL;DR: In this paper, the energy dispersion and the effective mass of the polaron with the 1/ε perturbation theory were calculated with the exact Monte Carlo method in the nonadiabatic and adiabatic regimes, respectively.
Abstract: small radius of the wave function but a large size of the lattice distortion. We calculate the energy dispersion and the effective mass of the polaron with the 1/� perturbation theory and with the exact Monte Carlo method in the nonadiabatic and adiabatic regimes, respectively. The "small" Frohlich polaron is found to be lighter than the small Holstein polaron by one or more orders of magnitude. A free electron interacting with the dielectric polaris- able continuum was studied by Pekar (1) and Frohlich (2) in the strong and weak coupling limit, respectively. This is the case of carriers interacting with optical phonons in ionic crystals under the condition that the size of the self-trapped state is large compared to the lattice con- stant so the lattice discreteness is irrelevant (3). The most sophisticated treatment of this "large" or "contin- uum" polaron is due to Feynman and co-workers (4) with the path-integral method, substantially extended in the past decade (5). This treatment leads to a mass enhance- ment, but not to a hopping conduction or to a narrow polaron band. When the electron-phonon coupling constantis large, all the states in the Brillouin zone are involved in the for- mation of the polaron wave function, so the polaron ra- dius becomes comparable with the lattice constant a and the continuum approximation is no longer valid. Basic features of the small polaron were well recognised a long time ago by Tjablikov (6), Yamashita and Kurosawa (7), Sewell (8), Holstein (9), Lang and Firsov (10) and oth- ers, and are described in several review papers and text- books (11-15). So far, analytical and numerical studies have been mainly confined to the Holstein model with a short-range electron-phonon interaction. Exact diag- onalization of several vibrating molecules coupled with one electron (16,17), variational (18,19) and Monte Carlo calculations (20) revealed an excellent agreement with an- alytical results of Holstein (9) and Lang and Firsov (10) for the energy of the ground state and first excited states at large �. Polaron mass is very large in the Holstein model, unless phonon frequencies are extremely high. The size of the region, where the small Holstein polaron is localised, is about the same as the size of the lattice distortion, each of the order of the lattice constant. Both sizes are almost identical also for the large Frohlich polaron, but much larger. In this Letter we study a problem of the lattice po- laron with a long-range Frohlich interaction (21). This quasiparticle has a small (atomic) size of the electron lo- calization region but a large size of the lattice distortion. While the large Frohlich polaron is heavier than the large Holstein polaron, the small Frohlich polaron (SFP) turns out to be much lighter than the small Holstein polaron (SHP) with the same binding energy. We argue that SFPs are relevant quasiparticles in the cuprates. A quite general electron-phonon lattice Hamiltonian with one electron and the "density-displacement" type of interaction is given by (9,12,15) H = − X nn' tnnc †'cn + X q� ¯q�(d †�dq� + 1/2)
157 citations
TL;DR: In this article, the lattice thermal conductivity in silicon quantum wires is theoretically investigated and it is shown that the bulk of heat in silicon structures is carried by acoustic phonons within a small region in the first Brillouin zone.
114 citations
TL;DR: In this paper, the optical modes of chains of coupled micron sized semiconductor cavities have been studied using photoluminescence spectroscopy and detailed calculations, showing that with an increasing number of cavities, the chains exhibit photon band gaps at several Brillouin zone boundaries.
Abstract: The optical modes of chains of coupled micron sized semiconductor cavities have been studied using photoluminescence spectroscopy and detailed calculations. With an increasing number of cavities, the chains exhibit photon band gaps at several Brillouin zone boundaries. The sizes of the band gaps are shown to depend on the coupling between the microcavities and also on the order of the Brillouin zone involved.
89 citations
TL;DR: In this article, structural and vibrational properties of pure GaN substrate grown using a lateral epitaxial overgrowth (LEO) technique were studied using x-ray diffraction, Brillouin, Raman, and infrared spectroscopy.
Abstract: Structural and vibrational properties of device quality pure GaN substrate grown using a lateral epitaxial overgrowth (LEO) technique were studied using x-ray diffraction, Brillouin, Raman, and infrared spectroscopy. Lattice constants were found to be a=3.1896±0.0002 A and c=5.1855±0.0002 A. Comparing the results with those on GaN epilayer directly grown on sapphire substrate, it is shown that the GaN substrate is indeed of high quality, i.e., the lattice is relaxed. However the GaN substrate has a small enough but finite residual strain arising from the pileup of the lateral growth front on SiO2 masks in the course of LEO. It was also found that the elastic stiffness constants C13 and C44, are more sensitive to the residual strain than the optical phonon frequencies. The high frequency and static dielectric constants were found to be 5.14 and 9.04. The Born and Callen effective charges were found to be 2.56 and 0.50.
83 citations
TL;DR: Through this analysis, it is determined numerically that the bandwidth of the Brillouin backscattered light becomes wider, and thus the measurement accuracy in determining the peak-power frequency degrades in approximately inverse proportion to the launched pulse width.
Abstract: We theoretically analyze the relation between the pulse width of light launched into an optical fiber and the resultant power spectrum of spontaneous Brillouin backscattered light. Through this analysis, we determine numerically that the bandwidth of the Brillouin backscattered light becomes wider, and thus the measurement accuracy in determining the peak-power frequency degrades in approximately inverse proportion to the launched pulse width. Experimental results with various pulse widths are in good agreement with the derived theoretical results.
76 citations
TL;DR: In this article, the authors show that the transition of BaCeO 3 to cubic perovskite is likely partly displacive and partly order-disorder. But the transition is not instantaneous.
TL;DR: In this article, the authors developed an automated system for strain measurements in a distributed sensing system that uses a novel signal processing technique to measure strain at resolutions finer than the Brillouin line width limit.
Abstract: It is known that the ultimate spatial resolution for a Brillouin-based sensor is limited by the lifetime of the phonons in the fiber that mediate the Brillouin loss process. At optical pulse widths less than 10 ns (corresponding to one meter spatial resolution) the Brillouin line width is considerably broadened, causing a severe penalty in resolving the Brillouin frequency shift. Around 5 ns the Brillouin line width is too broad to allow an accurate frequency determination. The fiber optics group at the University of New Brunswick, Canada, has recently developed an automated system for strain measurements in a distributed sensing system that uses a novel signal processing technique to measure strain at resolutions finer than the Brillouin line width limit. Strain has been resolved to 20 /spl mu//spl epsiv/ at 500 mm and to 40 /spl mu//spl epsiv/ at 250 mm.
TL;DR: In this article, the phonon structure of GaP quantum dots is studied using an atomistic potential model and the dot eigenmodes are obtained from a direct diagonalization of the dynamical matrix and classified using an efficient dual space analysis method.
Abstract: The phonon structure of GaP quantum dots is studied using an atomistic potential model. The dot eigenmodes are obtained from a direct diagonalization of the dynamical matrix and classified using an efficient dual-space analysis method. Our calculations provide a theoretical explanantion for several experimental observations. (1) Depending on the spatial localization, the phonon modes of dots are either dot-interior (bulklike) or surfacelike. (2) The frequencies of the dot-interior modes can be qualitatively described by the {open_quotes}truncated crystal method{close_quotes} using a single branch and a single wave vector of the bulk-phonon dispersion. In contrast, the surface modes cannot be described by this model. (3) The dot-interior modes have a dominant bulk parentage from a specific part of the Brillouin zone, while the surface modes do not. (4) The frequencies of the bulklike {Gamma}-derived longitudinal optical (LO) and transverse optical (TO) phonon modes are found to decrease with decreasing dot size. This decrease reflects the downward dispersion of the bulk optical-phonon branches away from the {Gamma} point. (5) The surface modes located between the bulk TO- and LO-phonon bands have a significant bulk {Gamma} character, and are thus Raman detectable. (6) The dot-interior modes exhibit only a slight LO/TO mode mixing, whilemore » the surfacelike modes show a strong mode mixing. {copyright} {ital 1999} {ital The American Physical Society}« less
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TL;DR: In this paper, the authors studied the renormalization group flow of the interactions in the two-dimensional t-t' Hubbard model near half filling in a N-patch representation of the whole Fermi surface.
Abstract: We study the renormalization group flow of the interactions in the two-dimensional t-t' Hubbard model near half filling in a N-patch representation of the whole Fermi surface. Starting from weak to intermediate couplings the flows are to strong coupling with different character depending on the choice of parameters. In a large parameter region elastic Umklapp scatterings drive an instability which on parts of the Fermi surface exhibits the key signatures of an insulating spin liquid (ISL), as proposed by Furukawa et al., rather than a conventional symmetry-broken state. The ISL is characterized by both strong d-wave pairing and antiferromagnetic correlations, however it is insulating due to the vanishing local charge compressibility and a spin liquid because of the spin gap arising from the pairing correlations. We find that the ISL is a consequence of a Fermi surface close to the saddle points at the Brillouin zone boundaries which provides an intrinsic and mutually reinforcing coupling between pairing and Umklapp channels.
TL;DR: In this paper, a new phase of WO3 with space group P4/ncc, a = 5.2885(5) A and c = 7.8626(8) A, was established, and its crystal structure was determined.
Abstract: At 1100 K a new phase of WO3 with space group P4/ncc, a = 5.2885(5) Aand c = 7.8626(8) A, was established, and its crystal structure was determined. The previously known tetragonal phase P4/nmm, which is shown to exist only above 1170 K, was also refined with a = 5.3031(4) Aand c = 3.9348(3) Aat 1200 K. The difference between the two perovskite-like structures relates to a tricritical non-ferroic transition characterized by a soft mode at the Z-point of the Brillouin zone, which induces antiphase rotations of the WO6 octahedra about [001]. The oxygen sublattice of the lower tetragonal structure is shown to possess the symmetry of the a0a0c- perovskite tilt structure F4/mmc (I4/mcm), which is violated by the off-centre antiferroelectric displacements of the tungsten atoms that lead to the observed space group P4/ncc.
TL;DR: In this article, the Brillouin light-scattering spectroscopy was used for spin-wave quantization in square arrays of micron-size circular magnetic Ni80Fe20 dots.
Abstract: We report on the observation of spin-wave quantization in square arrays of micron-size circular magnetic Ni80Fe20 dots by means of Brillouin light-scattering spectroscopy. For a large wave-vector interval several discrete, dispersionless modes with a frequency splitting of up to 2.5 GHz were observed. The modes are identified as magnetostatic surface spin waves laterally quantized due to in-plane confinement in each single dot. The frequencies of the lowest observed modes decrease with increasing distance between the dots, thus indicating an essential dynamic magnetic dipole interaction between the dots at small interdot distances.
TL;DR: In this article, a theoretical analysis of the phonon frequencies and polarization vectors at the Γ point of the Brillouin zone for LaMnO 3 Pnma phase necessary for the interpretation of Raman and infrared spectra has been carried out.
Abstract: A theoretical analysis of the phonon frequencies and polarization vectors at the Γ point of the Brillouin zone for LaMnO 3 Pnma phase necessary for the interpretation of Raman and infrared spectra has been carried out. The analysis is based on group theoretical analysis as well as on a lattice dynamical calculation. The calculation has been made in the framework of the effective-charge- rigid-ion model by using the short-range Born-Mayer and long-range Coulomb potentials. A comparative study of phonon modes of LaMnO 3 (Pnma phase) and La 2 CuO 4 (Cmca phase) has also been performed.
TL;DR: The study of the average structure of quasicrystals can be a valuable aid to the elucidation of the geometry of quAsicrystal-to-crystal transformations and contribute to the derivation of the physically most relevant Brillouin (Jones) zone.
Abstract: The non-crystallographic symmetry of d-dimensional (dD) quasiperiodic structures is incompatible with lattice periodicity in dD physical space. However, dD quasiperiodic structures can be described as irrational sections of nD (n > d) periodic hypercrystal structures. By appropriate oblique projection of particular hypercrystal structures onto physical space, discrete periodic average structures can be obtained. The boundaries of the projected atomic surfaces give the maximum distance of each atom in a quasiperiodic structure from the vertices of the reference lattice of its average structure. These maximum distances turn out to be smaller than even the shortest atomic bond lengths. The metrics of the average structure of a 3D Ammann tiling, for instance, with edge lengths of the unit tiles equal to the bond lengths in elemental aluminium, correspond almost exactly to the metrics of face-centred-cubic aluminium. This is remarkable since most stable quasicrystals contain aluminium as the main constitutent. The study of the average structure of quasicrystals can be a valuable aid to the elucidation of the geometry of quasicrystal-to-crystal transformations. It can also contribute to the derivation of the physically most relevant Brillouin (Jones) zone.
TL;DR: In this article, the authors studied the thermodynamic properties of the classical antiferromagnet on the kagom\'e lattice for the exactly solvable infinite-component spin-vector model, D \to \infty.
Abstract: Thermodynamic quantities and correlation functions (CFs) of the classical antiferromagnet on the kagom\'e lattice are studied for the exactly solvable infinite-component spin-vector model, D \to \infty. In this limit, the critical coupling of fluctuations dies out and the critical behavior simplifies, but the effect of would be Goldstone modes preventing ordering at any nonzero temperature is properly accounted for. In contrast to conventional two-dimensional magnets with continuous symmetry showing extended short-range order at distances smaller than the correlation length, r \propto 1/r^2 in the range a_0 << r << \xi_c \propto T^{-1/2}, where a_0 is the lattice spacing. Analytical results for the principal thermodynamic quantities in our model are in fairly good quantitative agreement with the MC simulations for the classical Heisenberg model, D=3. The neutron scattering cross section has its maxima beyond the first Brillouin zone; at T\to 0 it becomes nonanalytic but does not diverge at any q.
TL;DR: In this article, the Stokes feedback R was used to stabilize the steady Brillouin mirror regime in long-fiber ring laser systems. But the authors did not consider the self-pulsing mechanism.
Abstract: The nonlinear dynamics of cw-pumped Brillouin long-fiber ring lasers that contain a large number of longitudinal modes N beneath the Brillouin gain curve is controlled by a single parameter, namely, the Stokes feedback R. Below Rcrit, a stable train of dissipative solitonic pulses is spontaneously structured at the round-trip frequency fr without any additional intracavity mode locking. Experimental observations in cw-pumped fiber ring cavities, supported by numerical simulation in a coherent space–time three-wave model that includes the optical Kerr effect, prove the universality of the self-pulsing mechanism. Stability analysis shows that below Rcrit the steady Brillouin mirror regime is destabilized through a Hopf bifurcation. For R
TL;DR: In this paper, an experimental and theoretical study of the normal magnetic modes in spiral ferromagnetic structures is presented, which results in a structure similar to that encountered in a Bloch domain wall.
Abstract: An experimental and theoretical study is presented of the normal magnetic modes in spiral ferromagnetic structures. The bilayer system studied consists of Fe layers (25, 50, 100, and 200 A thick) that are exchange coupled to 200 A thick SmCo films that have ≈200 kOe anisotropies. The Fe spiral—induced by an external magnetic field that is applied opposite to the direction of the magnetized film—results in a structure similar to that encountered in a Bloch domain wall. The magnetization and the field dependence of the magnons in various Fe films are explained by the theoretical model.
TL;DR: In this article, a highly efficient extrapolative Brillouin-zone integration scheme is presented that requires a very low k-point sampling density for spectral integrations, since at low sampling densities interpolative schemes are hindered by problems associated with band crossing.
Abstract: A highly efficient extrapolative Brillouin-zone integration scheme is presented that requires a very low k-point sampling density for spectral integrations. It is important to use an extrapolative approach, since at low sampling densities interpolative schemes are hindered by problems associated with band crossing, which introduce spurious singularities in the density of states (DOS). The information for the extrapolation is obtained using second-order $\mathbf{k}\mathbf{\ensuremath{\cdot}}\mathbf{p}$ perturbation theory within a set of subcells of the Brillouin zone, which can be chosen to make full use of symmetry. The resulting piecewise quadratic representation of the band structure is converted directly to a DOS using an analytic approach. It is also shown that this method can be successfully applied even in the linear extrapolative case.
TL;DR: In this article, the wave vector dependence of Rayleigh and higher order Sezawa elastic waves in single crystalline epitaxial face-centered-cubic (fcc) Co layers are measured by Brillouin light scattering at room temperature.
Abstract: The wave vector dependence of Rayleigh and higher order Sezawa elastic waves in single crystalline epitaxial face-centered-cubic (fcc) Co layers are measured by Brillouin light scattering at room temperature. The dispersion of the mode velocities allows the independent elastic constants to be determined for this cubic phase of cobalt. These results compare very favorably to previous determinations of the elastic constants measured above 700 K from the high-temperature fcc phase of pure Co. Deviations from theoretical estimates are discussed.
TL;DR: In this paper, the temperature-dependent surface relaxation of Ag(111) is calculated by density-functional theory, and the equilibrium geometry is determined by minimizing the Helmholtz free energy within the quasiharmonic approximation.
Abstract: The temperature-dependent surface relaxation of Ag(111) is calculated by density-functional theory. At a given temperature, the equilibrium geometry is determined by minimizing the Helmholtz free energy within the quasiharmonic approximation. To this end, phonon dispersions all over the Brillouin zone are determined from density-functional perturbation theory. We find that the top-layer relaxation of Ag(111) changes from an inward contraction $(\ensuremath{-}0.8%)$ to an outward expansion $(+6.3%)$ as the temperature increases from $T=0\mathrm{K}$ to 1150 K, in agreement with experimental findings. Also, the calculated surface phonon dispersion curves at room temperature are in good agreement with helium-scattering measurements. The mechanism driving this surface expansion is analyzed, and the physical picture developed by Narasimhan and Scheffler is essentially confirmed.
TL;DR: In this article, a first-principles effective Hamiltonian was used to model the perovskite oxide KNbO3 and showed the prevalence of local polar distortions with short-range chain-like correlations, present even in the paraelectric phase.
Abstract: Molecular dynamics simulations of the perovskite oxide KNbO3 are performed with a first-principles effective Hamiltonian. They reveal the prevalence of local polar distortions with short-range chain-like correlations, present even in the paraelectric phase far above Tc. The ordering of these dynamically fluctuating distortions yields the observed temperature sequence of ferroelectric phases. The simulations also reproduce the essential features of diffuse x-ray scattering measurements and the weak temperature dependence of diffuse streak patterns observed by Comes et al. These local distortions suggest an order-disorder character for the transitions. Softening of optical phonon branches is observed in the same simulations not only near q = 0, suggesting a displacive character for the transition, but also over large regions of the Brillouin zone. Dynamic real-space chains thus provide a unified framework for understanding both the order-disorder and displacive characteristics of these phase transitions.
TL;DR: In this paper, it was shown that spin waves in an ordered quantum antiferromagnet in a strong magnetic field become unstable with respect to spontaneous two-magnon decays.
Abstract: We predict that spin waves in an ordered quantum antiferromagnet in a strong magnetic field become unstable with respect to spontaneous two-magnon decays. At zero temperature, the instability occurs between the threshold field ${H}^{*}$ and the saturation field ${H}_{c}$. As an example, we investigate the high-field dynamics of a Heisenberg antiferromagnet on a square lattice and show that the single-magnon branch of the spectrum disappears in most of the Brillouin zone.
01 Jan 1999
TL;DR: On-site distributed measurements using a sensor based on stimulated Brillouin scattering are presented in this paper, where long fiber length can be used, so that a dense 2D or 3D measurement of strain or temperature can be obtained in large structure.
Abstract: On-site distributed measurements using a sensor based on stimulated Brillouin scattering are presented. Long fibre length can be used, so that a dense 2D or 3D measurement of strain or temperature can be obtained in large structure.
TL;DR: In this article, the authors determined the possible symmetries for band (Bloch) states at various points of the Brillouin zone and the spin-orbit interaction has been taken into account.
Abstract: We determined the possible symmetries for band (Bloch) states at various points of the Brillouin zone. The spin–orbit interaction has been taken into account. Free excitons offer larger sets of possible state symmetries than single carriers do. The selection rules for the optical transitions have been established. Experiments with polarized light are shown to be relevant to study the nature (s or p) of A, B, and C excitons.
TL;DR: In this paper, the elastic properties of the films grown on silicon substrates under identical coating conditions have been de-termined by Brillouin light scattering from thermally excited surface phonons.