Mechanism of thermal conductivity reduction in few-layer graphene

Abstract

Using the linearized Boltzmann transport equation and perturbation theory, we analyze the reduction in the intrinsic thermal conductivity of few-layer graphene sheets accounting for all possible three-phonon scattering events. Even with weak coupling between layers, a significant reduction in the thermal conductivity of the out-of-plane acoustic modes is apparent.The main effect of this weak coupling is to open many new three-phonon scattering channels that are otherwise absent in graphene. However, reflection symmetry is only weakly broken with the addition of multiple layers, and ZA phonons still dominate thermal conductivity. We also find that reduction in thermal conductivity is mainly caused by lower contributions of the higher-order overtones of the fundamental out-of-plane acoustic mode. The results compare remarkably well over the entire temperature range with measurements of graphene and graphite.

Thermal conductivity of graphene mediated by strain and size

“…from the iterative approach is several-fold higher than those from the SMRTA [22,24], confirming previous findings [21,23] that both N-and U-processes and their relationship influencing the nonequilibrium populations of phonon modes are important for determining k of graphene. The convergence of k in our calculations for infinite unstrained graphene also justifies that intrinsic three-phonon scatterings can confine k, i.e., higher-order inter-phonon scatterings are not required for convergence of k as was previously suggested for k of unstrained single-walled carbon nanotubes [38,39].…”

“…A microscopic description of the lattice thermal conductivity k can be derived from BPE for phonons [21,22,24,34] in three-phonon scattering framework.…”

“…On the theoretical side, fundamental problems concerning the details of thermal transport in graphene have been subjects of debate [17][18][19][20][21][22][23][24][25][26][27][28][29][30], including the convergence behavior of k with system size, the extent of the diffusive and ballistic transport regimes, the role of flexural acoustic (ZA) phonons for thermal transport and strain effects on the convergence of k. It is generally believed that acoustic phonons [31] dominate the thermal transport in graphene. Based on this, 2D models give a logarithmic divergence with system size [27] but neglect the contributions from ZA phonons due to their low group velocities near the center of first Brillouin zone (FBZ) and their large Grüneisen parameters [32].…”

“…Therefore, intensive efforts have been committed to understand the underlying thermal transport physics in graphene experimentally [1,[5][6][7][8][9][10][11][12][13][14][15][16] and theoretically [2,[17][18][19][20][21][22][23][24][25][26][27][28][29][30].…”

Effects of interfacial roughness on phonon transport in bilayer silicon thin films

“…15,16 In additional to posing resistance to thermal transport in the direction that is normal to the vdW interface, phonon behavior at vdW interfaces could also have important effects to energy flow in the direction parallel to the vdW interface. For example, it has been shown that the in-plane thermal conductivity of multi-layer graphene 17 or supported graphene 8 is lower than that of suspended single-layer graphene, [17][18][19][20][21] which has been attributed to the interlayer phonon scattering or that between the supported graphene and the substrate. 17,[19][20][21][22] On the contrary, Guo et al's 23 and Ong et al's 24 results show that the coupling force plays an positive role in the enhancement of thermal conductivity.…”