Reduction of Thermal Conductivity by Nanoscale 3D Phononic Crystal

Yang, Lina; Yang, Nuo; Li, Baowen

doi:10.1038/srep01143

Cited by 50 publications

(49 citation statements)

References 36 publications

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“…To identify localized modes, we use the normalized inverse participation ratio (NIPR) [3], which is defined for eigenvectors u iα of a phonon k, as…”

Section: Resultsmentioning

confidence: 99%

“…Therefore knowledge of the phonon DOS at interfaces becomes of paramount interest for the basic understanding and engineering of low-dimensional devices. The VDOS in nanoscale multilayers, including the VDOS at interfaces, appears to be one of the important quantities for the description of the vibrational thermodynamics and phonon transport in such systems [3,4]. Furthermore, in order to recognize the significance of solid-solid interfaces, one should notice that interface-induced superconductivity appears to exist in epitaxial FeSe ultrathin films on SrTiO 3 (001) substrates [22] and interfacial mode coupling (most probably between optical SrTiO 3 phonons and FeSe electrons at the interface) was inferred as the origin of the enhancement of the superconducting transition temperature in FeSe/SrTiO 3 [23].…”

Section: Introductionmentioning

confidence: 99%

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Influence of interfaces on the phonon density of states of nanoscale metallic multilayers: Phonon confinement and localization

Keune

Hong

et al. 2018

Phys. Rev. B

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Isotope-selective 57 Fe nuclear resonant inelastic x-ray scattering (NRIXS) measurements and atomic-layer resolved density functional theory (DFT) calculations were used to investigate the effect of interfaces on the vibrational (phonon) density of states (VDOS) of (001)-oriented nanoscale Fe/Ag and Fe/Cr multilayers. The multilayers in the experiment contained isotopically enriched 57 Fe monolayers as probe layers located either at the Fe/Ag or Fe/Cr interfaces or in the center of the Fe films. This allows probing of the vibrational dynamics of Fe sites either at the buried interfaces or in the center of the Fe films. For Fe/Ag multilayers, distinct differences were observed experimentally between the Fe-partial VDOS at the interface and in the center. At the Fe/Ag interface, the high-energy longitudinal-acoustic (LA) phonon peak of Fe near ∼35 meV is suppressed and slightly shifted to lower energy, and the low-energy part of the VDOS below ∼20 meV is drastically enhanced, as compared to the Fe-specific VDOS in the center Fe layers or in bulk Fe. Similar phenomena are found to a less degree in the Fe/Cr multilayers. The measured Fe-partial VDOS was used to determine the Fe site-selective vibrational thermodynamic properties of the multilayers. Our theoretical findings for the layer-dependent VDOS of the multilayers are in qualitative agreement with the experimental results obtained by NRIXS. For Fe/Ag multilayers, which are characterized by a large atomic mass ratio, the experimental and theoretical results demonstrate phonon confinement in the Fe layers and phonon localization at the Fe/Ag interfaces due to the energy mismatch between Ag and Fe LA phonons. These phenomena are reduced or suppressed in the Fe/Cr multilayers with their about equal atomic masses. Moreover, direction-projected Fe VDOS along the (nearly in-plane) incident x-ray beam was computed in order to address the intrinsic vibrational anisotropy of the Fe/Ag multilayer. We have also performed spin-resolved electronic band structure (DFT) calculations, predicting an enhanced magnetic moment (μ Fe = 2.8 μ B ) of the interfacial Fe atoms and a high electron spin polarization (79%) at the Fermi energy for the Fe/Ag interface, as compared to the case of Fe center layers. This is a result of charge transfer from Fe to Ag at the interface. On the contrary, Cr tends to donate electrons to Fe, thus reducing the interfacial Fe moment (μ Fe = 1.9 μ B ). This implies strong chemical bonding at the Fe/Ag and Fe/Cr interfaces, affecting the interfacial VDOS.

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“…To identify localized modes, we use the normalized inverse participation ratio (NIPR) [3], which is defined for eigenvectors u iα of a phonon k, as…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of interfaces on the phonon density of states of nanoscale metallic multilayers: Phonon confinement and localization

Keune

Hong

et al. 2018

Phys. Rev. B

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“…By analogy to the photonic crystals, which are also known as photonic band gap materials as there are forbidden photon propagation frequencies [39,40], an artificially and periodically structured material could remove phonons of certain frequencies [41,36,42,43,44]. These phonon band gaps are due to scattering and interference phenomena, the latter being 40 known as coherent effects.…”

Section: Introductionmentioning

confidence: 99%

Heat transport in phononic-like membranes: Modeling and comparison with modulated nano-wires

Verdier

Lacroix

Termentzidis

2017

International Journal of Heat and Mass Transfer

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“…The phonon group velocities are obtained based on the phonon dispersion curves. The phonon participation ratio (P λ ) can be investigated by [36][37][38] å å e e = l a a l a l -…”

Section: Lattice Dynamics Simulationmentioning

confidence: 99%

Atomistic simulations of phonon behaviors in isotopically doped graphene with Sierpinski carpet fractal structure

Han

Fan

Wang

et al. 2020

Mater. Res. Express

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Two-dimensional (2D) graphene monolayer has been attached importance because of the fantastic physical properties. In this work, we conduct the atomistic simulations to evaluate the phonon behaviors in isotopically doped graphene with Sierpinski Carpet (SC) fractal structure. The thermal conductivities (k) with different fractal numbers are calculated by molecular dynamics simulation. The relationship between the k and the fractal number from 0 to 8 shows a first decreasing and then stable trend. The maximum reduction ratio of the k in SC fractal structures is 52.37%. Afterwards, we utilize the molecular dynamics simulation, phonon wave packet simulation and lattice dynamics simulation to investigate the phonon density of states (PDOS), energy transmission coefficient (ETC), phonon group velocity and participation ratio (PR) in SC fractal structures. In SC fractal structures, the PDOS increases in the low frequency region and the G-band will soften with the enhanced fractal number. We also observe that the isotopic doping atoms can lead to continuous reflected waves in SC fractal structure regions. Moreover, phonon modes in SC fractal structures possess the lower ETCs, phonon group velocities and PRs in comparison with the pristine graphene monolayer. Therefore, we attribute the lower k in SC fractal structures to the stronger phonon-impurity scattering and the increasing localized phonon modes.

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Reduction of Thermal Conductivity by Nanoscale 3D Phononic Crystal

Cited by 50 publications

References 36 publications

Influence of interfaces on the phonon density of states of nanoscale metallic multilayers: Phonon confinement and localization

Influence of interfaces on the phonon density of states of nanoscale metallic multilayers: Phonon confinement and localization

Heat transport in phononic-like membranes: Modeling and comparison with modulated nano-wires

Atomistic simulations of phonon behaviors in isotopically doped graphene with Sierpinski carpet fractal structure

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