We report the measurement of the thermal conductivity of a suspended single-layer graphene. The room temperature values of the thermal conductivity in the range ∼(4.84 ± 0.44) × 103 to (5.30 ± 0.48) × 103 W/mK were extracted for a single-layer graphene from the dependence of the Raman G peak frequency on the excitation laser power and independently measured G peak temperature coefficient. The extremely high value of the thermal conductivity suggests that graphene can outperform carbon nanotubes in heat conduction. The superb thermal conduction property of graphene is beneficial for the proposed electronic applications and establishes graphene as an excellent material for thermal management.

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Superior Thermal Conductivity of Single-Layer Graphene

There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.

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Graphene and Graphene Oxide: Synthesis, Properties, and Applications

We present a comprehensive, up-to-date compilation of band parameters for the technologically important III–V zinc blende and wurtzite compound semiconductors: GaAs, GaSb, GaP, GaN, AlAs, AlSb, AlP, AlN, InAs, InSb, InP, and InN, along with their ternary and quaternary alloys. Based on a review of the existing literature, complete and consistent parameter sets are given for all materials. Emphasizing the quantities required for band structure calculations, we tabulate the direct and indirect energy gaps, spin-orbit, and crystal-field splittings, alloy bowing parameters, effective masses for electrons, heavy, light, and split-off holes, Luttinger parameters, interband momentum matrix elements, and deformation potentials, including temperature and alloy-composition dependences where available. Heterostructure band offsets are also given, on an absolute scale that allows any material to be aligned relative to any other.

Band parameters for III–V compound semiconductors and their alloys

Recent years have seen a rapid growth of interest by the scientific and engineering communities in the thermal properties of materials. Heat removal has become a crucial issue for continuing progress in the electronic industry, and thermal conduction in low-dimensional structures has revealed truly intriguing features. Carbon allotropes and their derivatives occupy a unique place in terms of their ability to conduct heat. The room-temperature thermal conductivity of carbon materials span an extraordinary large range--of over five orders of magnitude--from the lowest in amorphous carbons to the highest in graphene and carbon nanotubes. Here, I review the thermal properties of carbon materials focusing on recent results for graphene, carbon nanotubes and nanostructured carbon materials with different degrees of disorder. Special attention is given to the unusual size dependence of heat conduction in two-dimensional crystals and, specifically, in graphene. I also describe the prospects of applications of graphene and carbon materials for thermal management of electronics.

Thermal properties of graphene and nanostructured carbon materials

Graphene’s success has shown that it is possible to create stable, single and few-atom-thick layers of van der Waals materials, and also that these materials can exhibit fascinating and technologically useful properties. Here we review the state-of-the-art of 2D materials beyond graphene. Initially, we will outline the different chemical classes of 2D materials and discuss the various strategies to prepare single-layer, few-layer, and multilayer assembly materials in solution, on substrates, and on the wafer scale. Additionally, we present an experimental guide for identifying and characterizing single-layer-thick materials, as well as outlining emerging techniques that yield both local and global information. We describe the differences that occur in the electronic structure between the bulk and the single layer and discuss various methods of tuning their electronic properties by manipulating the surface. Finally, we highlight the properties and advantages of single-, few-, and many-layer 2D materials in...

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Progress, Challenges, and Opportunities in Two-Dimensional Materials Beyond Graphene

elphbolt is a modern Fortran (2018 standard) code for efficiently solving the coupled electron-phonon Boltzmann transport equations from first principles. Using results from density functional and density functional perturbation theory as inputs, it can calculate the effect of the non-equilibrium phonons on the electronic transport (phonon drag) and non-equilibrium electrons on the phononic transport (electron drag) in a fully self-consistent manner and obeying the constraints mandated by thermodynamics. It can calculate the lattice, charge, and thermoelectric transport coefficients for the temperature gradient and electric fields, and the effect of the mutual electron-phonon drag on these transport properties. The code fully exploits the symmetries of the crystal and the transport-active window to allow the sampling of extremely fine electron and phonon wave vector meshes required for accurately capturing the drag phenomena. The coarray feature of modern Fortran, which offers native and convenient support for parallelization, is utilized. The code is compact, readable, well-documented, and extensible by design.

Elphbolt: An ab initio solver for the coupled electron-phonon Boltzmann transport equations.

A quantitative description of the power factor for thermoelectric transport in quantum well and quantum wire superlattices has been developed. The size dependence of the carrier scattering rates as well as carrier tunneling between layers are included, and results are obtained for full three-dimensional superlattice systems. In addition, model calculations of the lattice thermal conductivity of free standing wells and wires have been obtained, and their implications for the thermoelectric figure of merit are discussed. Illustrative results are given for GaAs and PbTe systems.

Thermoelectric Transport in Superlattices

The thermal conductivity is a fundamental thermal transport parameter that describes the ability of a material to conduct heat. This chapter focuses on ab initio theoretical approaches to calculate the lattice thermal conductivity κ, where heat is carried by phonons. Thermal conductivity κ determines the utility of materials for specific thermal management applications. Materials with low thermal conductivity find applicability in, for example, efficient thermoelectric (TE) cooling and power generation devices, while materials with high thermal conductivity are needed for passive cooling of microelectronics. If modes with small density of states substantially contribute to heat conduction, as occurs in silicon, these phonons are unlikely to be sampled, leading to large noise for certain phonon frequencies. The task of engineering phonon transport is particularly difficult because of the lack of simulation tools to describe heat conduction in the complex microstructure of realistic TE crystals.

Simulation of Phonons

: The research performed during the period of funding can be categorized into two areas. First, a theoretical investigation of the optical properties of strained layer quantum wells grown along the 111 crystallographic direction, and second, an examination of the far infrared response of quantum dot systems. (Author)

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Theory of the Electronic and Optical Properties of Semiconductor Heterostructures

The tremendous advances in electronics technology have been made possible through the study and characterization of the optical and electronic properties of novel semiconductor materials, such as quantum wells, heterojunctions and superlattices. In this paper, we review some of the basic properties of these systems.

David Broido

Papers

Elphbolt: An ab initio solver for the coupled electron-phonon Boltzmann transport equations.

Thermoelectric Transport in Superlattices

Simulation of Phonons

Theory of the Electronic and Optical Properties of Semiconductor Heterostructures

Electronic and Optical Properties of Lower-Dimensional Semiconductor Systems