Anomalous Size Dependence of the Thermal Conductivity of Graphene Ribbons

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• 作者：Denis L. Nika ; Artur S. Askerov ; Alexander A. Balandin
• 刊名：Nano Letters
• 出版年：2012
• 出版时间：June 13, 2012
• 年：2012
• 卷：12
• 期：6
• 页码：3238-3244
• 全文大小：399K
• 年卷期：v.12,no.6(June 13, 2012)
• ISSN：1530-6992

文摘

We investigated the thermal conductivity K of graphene ribbons and graphite slabs as the function of their lateral dimensions. Our theoretical model considered the anharmonic three-phonon processes to the second-order and included the angle-dependent phonon scattering from the ribbon edges. It was found that the long mean free path of the long-wavelength acoustic phonons in graphene can lead to an unusual nonmonotonic dependence of the thermal conductivity on the length L of a ribbon. The effect is pronounced for the ribbons with the smooth edges (specularity parameter p > 0.5). Our results also suggest that, contrary to what was previously thought, the bulk-like three-dimensional phonons in graphite make a rather substantial contribution to its in-plane thermal conductivity. The Umklapp-limited thermal conductivity of graphite slabs scales, for L below 30 渭m, as log(L), while for larger L, the thermal conductivity approaches a finite value following the dependence K₀ 鈥?A 脳 L^-1/2, where K₀ and A are parameters independent of the length. Our theoretical results clarify the scaling of the phonon thermal conductivity with the lateral sizes in graphene and graphite. The revealed anomalous dependence K(L) for the micrometer-size graphene ribbons can account for some of the discrepancy in reported experimental data for graphene.

Keywords:

Graphene ribbons; thermal conductivity; phonon transport; graphite slabs