Abstract
We review the results of our experimental investigation of heat conduction in suspended graphene and offer a theoretical interpretation of its extremely high thermal conductivity. The direct measurements of the thermal conductivity of graphene were performed using a non-contact optical technique and special calibration procedure with bulk graphite. The measured values were in the range of ∼3000–5300 W mK−1 near room temperature and depended on the lateral dimensions of graphene flakes. We explain the enhanced thermal conductivity of graphene as compared to that of bulk graphite basal planes by the two-dimensional nature of heat conduction in graphene over the whole range of phonon frequencies. Our calculations show that the intrinsic Umklapp-limited thermal conductivity of graphene grows with the increasing dimensions of graphene flakes and can exceed that of bulk graphite when the flake size is on the order of a few micrometers. The detailed theory, which includes the phonon-mode-dependent Gruneisen parameter and takes into account phonon scattering on graphene edges and point defects, gives numerical results that are in excellent agreement with the measurements for suspended graphene. Superior thermal properties of graphene are beneficial for all proposed graphene device applications.
Highlights
We review the results of our experimental investigation of heat conduction in suspended graphene and offer a theoretical interpretation of its extremely high thermal conductivity
Since none of the conventional methods for the thermal conductivity measurement works for graphene, we developed our own non-contact optical approach
We found that the G peak of graphene’s Raman spectra exhibits strong temperature dependence [5, 6]. The latter means that the shift in the position of G peak in response to laser heating can be used for measuring the local temperature rise
Summary
Since none of the conventional methods for the thermal conductivity measurement works for graphene, we developed our own non-contact optical approach. The correlation between the temperature rise and amount of power dissipated in graphene, for the sample with given geometry and proper heat sinks, can give the value of the thermal conductivity K (see the schematic of the experiment in figure 1(a)). The single-layer graphene flakes were selected using the micro Raman spectroscopy by checking the intensity ratio of G and 2D peaks and by 2D band deconvolution [10]–[13]. The power absorbed in graphene is determined through the ratio of the integrated Raman intensities of graphene and bulk graphite. The calibration and measurement of the absorbed power is illustrated in figure 2 It is based on comparison of the experimentally determined integrated Raman intensity for the G peak from the singlelayer graphene and bulk graphite. The RT position of the G peak was verified for all samples
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