Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

Kargar, Fariborz; Ramirez, S.; Debnath, Bishwajit; Malekpour, Hoda; Lake, Roger K.; Balandin, Alexander A.

doi:10.1063/1.4934883

Cited by 35 publications

(37 citation statements)

References 40 publications

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“…Nevertheless, the full representation of the BLS experiment is the correct approach to yield the elastic and photoelastic parameters of the hPnC constituent components at nanoscale. 28 We have also examined an alternative approach assuming a solidification of F next to the wall. 30 A thin ($10 nm) solidified layer at the interface with low transverse acoustic velocity ($100 m/s) creates few additional features (flat branches) in the band diagram but are not identifiable among the experimental branches.…”

Section: -mentioning

confidence: 99%

“…In this work, we use the femtosecond laser 2PP to fabricate square lattice hPnCs based on the zirconium propoxide (ZPO)-based hybrid sol-gel photosensitive material. 26 There are few reports on cavity-type hPnCs with cylindrical nanopores, e.g., with a single crystalline epoxy/air sample, 18 anodic porous alumina containing hexagonal arrays of aligned nanopores oriented normal to the film surface, 27,28 and square arrays of holes of Si-membranes. 29 Using Brillouin light scattering spectroscopy (BLS) in transmission geometry (see Fig.…”

mentioning

confidence: 99%

“…30 In the former case, there was no direct comparison with the theoretical band diagram, while in the latter this comparison was restricted on the observed phononic branches. For the semi-or non-transparent hPnCs, 28,29 BLS was employed in backscattering geometry where the ripple mechanism dominated the scattering from the surface. For a fundamental understanding, however, the theoretical representation of the full BLS spectrum, frequencies, and intensities is necessary.…”

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confidence: 99%

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Band structure of cavity-type hypersonic phononic crystals fabricated by femtosecond laser-induced two-photon polymerization

Rakhymzhanov

Gueddida

Alonso-Redondo

et al. 2016

Applied Physics Letters

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The phononic band diagram of a periodic square structure fabricated by femtosecond laser pulse-induced two photon polymerization is recorded by Brillouin light scattering (BLS) at hypersonic (GHz) frequencies and computed by finite element method. The theoretical calculations along the two main symmetry directions quantitatively capture the band diagrams of the air- and liquid-filled structure and moreover represent the BLS intensities. The theory helps identify the observed modes, reveals the origin of the observed bandgaps at the Brillouin zone boundaries, and unravels direction dependent effective medium behavior.

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Section: -mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Band structure of cavity-type hypersonic phononic crystals fabricated by femtosecond laser-induced two-photon polymerization

Rakhymzhanov

Gueddida

Alonso-Redondo

et al. 2016

Applied Physics Letters

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“…Details of our BMS measurement procedures have been reported elsewhere. [16][17][18] In order to observe the interference effects, the amplitudes of the interfering spin waves should be approximately the same at the point of observation. The amplitude of the spin wave signal decreases exponentially with the distance from the generating antenna.…”

Section: Brillouin-mandelstam Spectroscopy Measurementsmentioning

confidence: 99%

Brillouin-Mandelstam spectroscopy of standing spin waves in a ferrite waveguide

et al. 2017

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This article reports results of experimental investigation of the spin wave interference over large distances in the Y3Fe2(FeO4)3 waveguide using Brillouin-Mandelstam spectroscopy. Two coherent spin waves are excited by the micro-antennas fabricated at the edges of the waveguide. The amplitudes of the input spin waves are adjusted to provide approximately the same intensity in the central region of the waveguide. The relative phase between the excited spin waves is controlled by the phase shifter. The change of the local intensity distribution in the standing spin wave is monitored using Brillouin-Mandelstam light scattering spectroscopy. Experimental data demonstrate the oscillation of the scattered light intensity depending on the relative phase of the interfering spin waves. The oscillations of the intensity, tunable via the relative phase shift, are observed as far as 7.5 mm away from the spin-wave generating antennas at room temperature. The obtained results are important for developing techniques for remote control of spin currents, with potential applications in spin-based memory and logic devices.

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“…The degree of transport suppression is dictated by the relationship between the characteristic length of the material and the dominant phonon mean free path (MFP) [4]. For example, recent experiments have demonstrated very low thermal conductivities in thin films [5], nanowires [6,7], and porous materials [8][9][10][11][12][13], illustrating the effectiveness of boundary engineering in tuning thermal transport [14].…”

Section: Introductionmentioning

confidence: 99%

Thermal anisotropy enhanced by phonon size effects in nanoporous materials

Romano

Kolpak

2017

Applied Physics Letters

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While thermal anisotropy is a desirable materials property for many applications, including transverse thermoelectrics and thermal management in electronic devices, it remains elusive in practical natural compounds. In this work, we show how nanoporous materials with anisotropic pore lattices can be used as a platform for inducing strong heat transport directionality in isotropic materials. Using density functional theory and the phonon Boltzmann transport equation, we calculate the phonon-size effects and thermal conductivity of nanoporous silicon with different anisotropic pore lattices. Our calculations predict a strong directionality in the thermal conductivity, dictated by the difference in the pore-pore distances, i.e. the phonon bottleneck, along the two Cartesian axes. Using Fourier's law, we also compute diffusive heat transport for the same geometries obtaining significantly smaller anisotropy, revealing the crucial role of phonon-size effects in tuning thermal transport directionality. Besides enhancing our understanding of nanoscale heat transport, our results demonstrate the promise of nanoporous materials for modulating anisotropy in thermal conductivity.

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Acoustic phonon spectrum and thermal transport in nanoporous alumina arrays

Cited by 35 publications

References 40 publications

Band structure of cavity-type hypersonic phononic crystals fabricated by femtosecond laser-induced two-photon polymerization

Band structure of cavity-type hypersonic phononic crystals fabricated by femtosecond laser-induced two-photon polymerization

Brillouin-Mandelstam spectroscopy of standing spin waves in a ferrite waveguide

Thermal anisotropy enhanced by phonon size effects in nanoporous materials

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