Thermal conductivity of graphene with defects induced by electron beam irradiation

Abstract

We investigate the thermal conductivity of suspended graphene as a function of the density of defects, ND, introduced in a controllable way. High-quality graphene layers are synthesized using chemical vapor deposition, transferred onto a transmission electron microscopy grid, and suspended over ∼7.5 μm size square holes. Defects are induced by irradiation of graphene with the low-energy electron beam (20 keV) and quantified by the Raman D-to-G peak intensity ratio. As the defect density changes from 2.0 × 10(10) cm(-2) to 1.8 × 10(11) cm(-2) the thermal conductivity decreases from ∼(1.8 ± 0.2) × 10(3) W mK(-1) to ∼(4.0 ± 0.2) × 10(2) W mK(-1) near room temperature. At higher defect densities, the thermal conductivity reveals an intriguing saturation-type behavior at a relatively high value of ∼400 W mK(-1). The thermal conductivity dependence on the defect density is analyzed using the Boltzmann transport equation and molecular dynamics simulations. The results are important for understanding phonon - point defect scattering in two-dimensional systems and for practical applications of graphene in thermal management.

Ultrastiff, Strong, and Highly Thermally Conductive Crystalline Graphitic Films with Mixed Stacking Order

“…As a result, assembling these wet‐transferred graphene layers into a stacked structure is likely to result in a defective material due to defects in plane and interstitial contamination between layers. The defects are detrimental for optimal electrical as well as mechanical and thermal properties …”

“…The defects are detrimental for optimal electrical as well as mechanical and thermal properties. [19,20] Here, we have made centimeter-scale crystalline films by stacking 100 layers of CVD-grown graphene, with the resulting film demonstrating significantly higher stiffness, fracture strength, and thermal conductivity than any other macroscale film composed of only graphene or graphite without other constituents. The freestanding film sample resulting from layer-by-layer stacking was subjected to successive annealing treatments of 400 °C (SG400), 2000 °C (SG2000), and 2800 °C (SG2800) in Ar for two hours at each temperature (see timetemperature profile in Figure S1 of the Supporting Information), and the evolution from stacked but discrete layers of graphene to a new macroscale synthetic material was studied.…”

Phonon thermal conduction in novel 2D materials

“…This technique provides direct measurement of intrinsic thermal resistance of nanowires and supported graphene, however extension of such technique to suspended 2D materials has not been reported. Due to the challenges discussed above, and in additional to the effect from defects [81,82], rough edges, thickness non-uniformity and lateral sizes (length and width), the measured thermal conductivity in 2D materials differ from groups to groups and its value scatters in several folds, leaving the intrinsic thermal properties of 2D materials unsolved with hot debates and arguments to date. Furthermore, complex nanofabrication process is applied to transfer 2D materials to prepatterned nanostructures suitable for thermal measurement.…”

Raman study of the substrate influence on graphene synthesis using a solid carbon source via rapid thermal annealing

“…The films are usually characterized by Raman microspectroscopy, a recognized technique for investigating the nanostructure, crystallite size, defects, and number of layers in graphene materials. [39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58] Specifically, surface mapping of the Raman signal is performed to accurately assess the homogeneity of the samples at the micrometric scale. Raman spectra of carbon materials typically exhibit numerous contributions, among which three are of major significance for studying graphene: the so-called D, G, and 2D peaks appearing, respectively, at shifts around 1,350, 1,580, and 2,700 cm −1 .…”