Lucas Lindsay

Two-Dimensional Phonon Transport in Supported Graphene

Heat Flow in Graphene Unsupported graphene sheets show exceptional thermal transport properties, but are these properties maintained when a graphene sheet is in contact with a substrate? Seol et al. (p. 213; see the Perspective by Prasher) measured the thermal conductivity of graphene supported on silicon dioxide and found that, while the conductivity was considerably lower than that of free-standing graphene, it was still greater than that of metals such as copper. A theoretical model suggested that the out-of-plane flexing vibrations of the graphene play a key role in thermal transport. Thus, graphene may help in applications such as conducting heat away from electronic circuits. The thermal conductivity of graphene supported on silicon dioxide remains high, despite phonon scattering by the substrate. The reported thermal conductivity (κ) of suspended graphene, 3000 to 5000 watts per meter per kelvin, exceeds that of diamond and graphite. Thus, graphene can be useful in solving heat dissipation problems such as those in nanoelectronics. However, contact with a substrate could affect the thermal transport properties of graphene. Here, we show experimentally that κ of monolayer graphene exfoliated on a silicon dioxide support is still as high as about 600 watts per meter per kelvin near room temperature, exceeding those of metals such as copper. It is lower than that of suspended graphene because of phonons leaking across the graphene-support interface and strong interface-scattering of flexural modes, which make a large contribution to κ in suspended graphene according to a theoretical calculation.

Optimized Tersoff and Brenner empirical potential parameters for lattice dynamics and phonon thermal transport in carbon nanotubes and graphene

We have examined the commonly used Tersoff and Brenner empirical interatomic potentials in the context of the phonon dispersions in graphene. We have found a parameter set for each empirical potential that provides improved fits to some structural data and to the in-plane phonon dispersion data for graphite. These optimized parameter sets yield values of the acoustic phonon velocities that are in better agreement with measured data. They also provide lattice thermal conductivity values in single-walled carbon nanotubes that are considerably improved compared to those obtained from the original parameter sets.

Physically founded phonon dispersions of few-layer materials and the case of borophene

ABSTRACT By building physically sound interatomic force constants, we offer evidence of the universal presence of a quadratic phonon branch in all unstrained 2D materials, thus contradicting much of the existing literature. Through a reformulation of the interatomic force constants (IFCs) in terms of internal coordinates, we find that a delicate balance between the IFCs is responsible for this quadraticity. We use this approach to predict the thermal conductivity of Pmmn borophene, which is comparable to that of , and displays a remarkable in-plane anisotropy. These qualities may enable the efficient heat management of borophene devices in potential nanoelectronic applications. IMPACT STATEMENT The newly found universality of quadratic dispersion will change the way 2D-material phonons are calculated. Predicted results for borophene shall become a fundamental reference for future research on this material. GRAPHICAL ABSTRACT

Thermal conductivity of graphene mediated by strain and size

Based on first-principles calculations and full iterative solution of the linearized Boltzmann-Peierls transport equation for phonons within three-phonon scattering framework, we characterize the lattice thermal conductivities

Unusual Enhancement in Intrinsic Thermal Conductivity of Multilayer Graphene by Tensile Strains

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First Principles Peierls-Boltzmann Phonon Thermal Transport: A Topical Review

of strained and unstrained graphene. We find

Reexamination of basal plane thermal conductivity of suspended graphene samples measured by electro-thermal micro-bridge methods

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Role of low-energy phonons with mean-free-paths >0.8 μm in heat conduction in silicon

converges to 5450 W/m-K for infinite unstrained graphene, while

The Seebeck coefficient and phonon drag in silicon

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Electronic structure and electron-phonon coupling in TiH2.

diverges for strained graphene with increasing system size at room temperature. The different