Acoustic barriers and observation of guided elastic waves in GaN-AlN structures by Brillouin scattering

Chirita, M.; Sooryakumar, R.; Venugopal, R.; Wan, Jian Wei; Melloch, M. R.

doi:10.1103/physrevb.63.205302

Cited by 14 publications

(7 citation statements)

References 20 publications

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“…The relatively weak dependence of the frequency on diameter is associated with a lack of significant variation of displacements over the cross section. This mode is analogous to longitudinal guided modes observed in BLS measurements on transparent thin films, including GaN-AlN [54]. Chirita et al [54], found that inelastic light scattering from longitudinal guided modes in GaN occurs primarily through elasto-optic coupling.…”

Section: Discussionmentioning

confidence: 60%

“…This mode is analogous to longitudinal guided modes observed in BLS measurements on transparent thin films, including GaN-AlN [54]. Chirita et al [54], found that inelastic light scattering from longitudinal guided modes in GaN occurs primarily through elasto-optic coupling. Therefore, the emergence of the longitudinal A 1 mode in our measured spectra at higher wavenumbers (with the wavevector of the incident light within ∼45 • of the hexagonal axis of the nanowires) suggests an increased contribution of elasto-optic scattering at these wavenumbers.…”

Section: Discussionmentioning

confidence: 60%

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Vibrational modes of GaN nanowires in the gigahertz range

et al. 2012

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Brillouin-light-scattering measurements and finite-element modeling of vibrational spectra in the range of 5-40 GHz are presented for an array of monocrystalline GaN nanowires with hexagonal cross sections. Analysis of the spectra is substantially complicated by the presence of a distribution of nanowire diameters. The measurements and calculations reveal a variety of modes with simple flexural, higher-order flexural, approximately 'plane-strain', approximately longitudinal and torsional displacement patterns that are similar to the corresponding modes of isotropic cylinders. The largest peaks in the spectra with acoustic angular wavenumbers in the range of 4 to ~15 μm(-1) were determined to arise from modes with relatively large transverse displacements, consistent with inelastic light scattering arising predominantly from surface ripple. These dominant modes have finite frequencies in the limit of zero wavenumber, corresponding to transverse standing waves. At higher wavenumbers, the spectra provide evidence for increased scattering through elasto-optic coupling, especially with respect to the emergence of a peak from a mode analogous to the longitudinal guided modes of thin films.

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Section: Discussionmentioning

confidence: 60%

Section: Discussionmentioning

confidence: 60%

Vibrational modes of GaN nanowires in the gigahertz range

et al. 2012

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“…Longitudinal guided modes have, for instance, been observed in a ZnSe supported film 46 and a GaN-AlN supported bilayer. 47 The longitudinal guided modes at high hq // are therefore not related to the interface between the SL and the substrate and can exist even in free-standing films (Fig. S2 of the supplementary material).…”

Section: In-plane Propagationmentioning

confidence: 99%

Direction-dependent elastic properties and phononic behavior of PMMA/BaTiO3 nanocomposite thin films

Alonso-Redondo

Gueddida

Huesmann

et al. 2017

The Journal of Chemical Physics

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Determination of the anisotropic mechanical properties of nanostructured hybrid films is of great importance to improve fabrication and to enable reliable utility. Here, we employ spontaneous Brillouin light spectroscopy to record the phononic dispersion relation along the two symmetry directions in a supported PMMA (poly(methylmethacrylate))-BaTiO hybrid superlattice (SL) with a lattice constant of about 140 nm. Several dispersive elastic modes are resolved for in-plane wave propagation, whereas along the periodicity direction the SL opens a wide propagation stop band for hypersonic phonons and near UV photons both centered at about 280 nm. A thorough theoretical analysis based on the finite element method quantitatively captures the band diagrams along the two main symmetry directions, helps identify the large density mismatch effect on the unexpectedly low sound phase velocity, and reveals significant anisotropy of the SL elastic tensor. Phonon propagation is a sensitive index of the structure, density, and the mechanical moduli of nanocomposite films.

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“…19 The interaction of these modes with light arises from the elasto-optic effect. 20 The possibility of detecting the SH waves depends on the polarization of the light and the scattering geometry.…”

Section: B Polarization Mixturementioning

confidence: 99%