Probing limits of acoustic nanometrology using coherent extreme ultraviolet light

Nardi, Damiano; Hoogeboom-Pot, Kathleen; Hernández-Charpak, Jorge N.; Tripp, Marie; King, Sean W.; Anderson, Erik H.; Murnane, Margaret M.; Kapteyn, Henry C.

doi:10.1117/12.2011194

“…Examples of this dynamic signal are shown in Fig. 2A. [Note that more details of the experimental setup are described elsewhere (13,14) and in SI Text, section S1.] Because the reflectivities of these materials do not change with temperature at EUV wavelengths (15), the change in the diffraction signal can be uniquely attributed to physical deformations in the surface profile.…”

Section: Methodsmentioning

confidence: 99%

“…Thus, the data of Fig. 2A can be used to directly extract the average thermal expansion and relaxation of each individual nanowire induced by laser heating and subsequent heat dissipation into the substrate, in addition to the surface deformations caused by acoustic waves launched by the initial impulsive expansion (13,14,17).…”

Section: Methodsmentioning

confidence: 99%

A new regime of nanoscale thermal transport: Collective diffusion increases dissipation efficiency

Hoogeboom-Pot

¹

,

Hernández-Charpak

²

,

Gu

³

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Understanding thermal transport from nanoscale heat sources is important for a fundamental description of energy flow in materials, as well as for many technological applications including thermal management in nanoelectronics and optoelectronics, thermoelectric devices, nanoenhanced photovoltaics, and nanoparticle-mediated thermal therapies. Thermal transport at the nanoscale is fundamentally different from that at the macroscale and is determined by the distribution of carrier mean free paths and energy dispersion in a material, the length scales of the heat sources, and the distance over which heat is transported. Past work has shown that Fourier's law for heat conduction dramatically overpredicts the rate of heat dissipation from heat sources with dimensions smaller than the mean free path of the dominant heat-carrying phonons. In this work, we uncover a new regime of nanoscale thermal transport that dominates when the separation between nanoscale heat sources is small compared with the dominant phonon mean free paths. Surprisingly, the interaction of phonons originating from neighboring heat sources enables more efficient diffusive-like heat dissipation, even from nanoscale heat sources much smaller than the dominant phonon mean free paths. This finding suggests that thermal management in nanoscale systems including integrated circuits might not be as challenging as previously projected. Finally, we demonstrate a unique capability to extract differential conductivity as a function of phonon mean free path in materials, allowing the first (to our knowledge) experimental validation of predictions from the recently developed first-principles calculations.nanoscale thermal transport | nondiffusive transport | mean free path spectroscopy | high harmonic generation | ultrafast X-rays C ritical applications including thermoelectrics for energy harvesting, nanoparticle-mediated thermal therapy, nanoenhanced photovoltaics, and thermal management in integrated circuits require a comprehensive understanding of energy flow at the nanoscale. Recent work has shown that the rate of heat dissipation from a heat source is reduced significantly below that predicted by Fourier's law for diffusive heat transfer when the characteristic dimension of the heat source is smaller than the mean free path (MFP) of the dominant heat carriers (phonons in dielectric and semiconductor materials) (1-6). However, a complete fundamental description of nanoscale thermal transport is still elusive, and current theoretical efforts are limited by a lack of experimental validation.Diffusive heat transfer requires many collisions among heat carriers to establish a local thermal equilibrium and a continuous temperature gradient along which energy dissipates. However, when the dimension of a heat source is smaller than the phonon MFP, the diffusion equation is intrinsically invalid because phonons move ballistically without collisions. The rate of nanoscale heat dissipation is significantly lower than the diffusive prediction such that smaller heat ...

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“…2a. (Note that more details of the experimental setup are described elsewhere 12,13 and in Supplementary Section S1). Because the reflectivities of these materials do not change with temperature at EUV wavelengths 14 , the change in the diffraction signal can be uniquely attributed to physical deformations in the surface profile.…”

Section: Methodsmentioning

confidence: 99%

“…Thus, the data of Fig. 2a can be used to directly extract the average thermal expansion and relaxation of each individual nanowire induced by laser heating and subsequent heat dissipation into the substrate, in addition to the surface deformations caused by acoustic waves launched by the initial impulsive expansion 12,13,15 .…”

Section: Methodsmentioning

confidence: 99%

A New Regime of Nanoscale Thermal Transport: Collective Diffusion Counteracts Dissipation Inefficiency

Hoogeboom-Pot

¹

,

Hernández-Charpak

²

,

Anderson

³

et al. 2015

Springer Proceedings in Physics

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Understanding thermal transport from nanoscale heat sources is important for a fundamental description of energy flow in materials, as well as for many technological applications including thermal management in nanoelectronics, thermoelectric devices, nano-enhanced photovoltaics and nanoparticle-mediated thermal therapies. Thermal transport at the nanoscale is fundamentally different from that at the macroscale and is determined by the distribution of carrier mean free paths in a material, the length scales of the heat sources, and the distance over which heat is transported. Past work has shown that Fourier's law for heat conduction dramatically over-predicts the rate of heat dissipation from heat sources with dimensions smaller than the mean free path of the dominant heat-carrying phonons. In this work, we uncover a new regime of nanoscale thermal transport that dominates when the separation between nanoscale heat sources is small compared with the dominant phonon mean free paths. Surprisingly, the interplay between neighboring heat sources can facilitate efficient, diffusive-like heat dissipation, even from the smallest nanoscale heat sources. This finding suggests that thermal management in nanoscale systems including integrated circuits might not be as challenging as projected. Finally, we demonstrate a unique and new capability to extract mean free path distributions of phonons in materials, allowing the first experimental validation of differential conductivity predictions from first-principles calculations.2

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“…[8][9][10] Excitation of hypersonic frequency SAWs in SPCs has been achieved by means of time-resolved all-optical techniques, [11][12][13][14][15] lately reaching SAW confinements of few tens of nm. [16][17][18][19] In this regime, SAW-generation in optically excited SPCs has been recently applied to the characterization of the elastic properties of hard thin-films 19 and to alternative mass-sensing schemes, enabling superior sensitivities. 20 In order to widen the spectrum of applications, excitation of interface confined acoustic modes in SPCs made of soft materials is envisaged.…”

mentioning

confidence: 99%

Interface nano-confined acoustic waves in polymeric surface phononic crystals

Travagliati

¹

,

Nardi

²

,

Giannetti

³

et al. 2015

Applied Physics Letters

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The impulsive acoustic dynamics of soft polymeric surface phononic crystals is investigated here in the hypersonic frequency range by near-IR time-resolved optical diffraction. The acoustic response is analysed by means of wavelet spectral methods and finite element modeling. An unprecedented class of acoustic modes propagating within the polymer surface phononic crystal and confined within 100 nm of the nano-patterned interface is revealed. The present finding opens the path to an alternative paradigm for characterizing the mechanical properties of soft polymers at interfaces and for sensing schemes exploiting polymers as embedding materials.

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Probing limits of acoustic nanometrology using coherent extreme ultraviolet light

Cited by 9 publications

References 21 publications

A new regime of nanoscale thermal transport: Collective diffusion increases dissipation efficiency

A new regime of nanoscale thermal transport: Collective diffusion increases dissipation efficiency

A New Regime of Nanoscale Thermal Transport: Collective Diffusion Counteracts Dissipation Inefficiency

Interface nano-confined acoustic waves in polymeric surface phononic crystals

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