Abstract
High basal plane thermal conductivity k of multi-layer graphene makes it promising for thermal management applications. Here we examine the effects of tensile strain on thermal transport in this system. Using a first principles Boltzmann-Peierls equation for phonon transport approach, we calculate the room-temperature in-plane lattice k of multi-layer graphene (up to four layers) and graphite under different isotropic tensile strains. The calculated in-plane k of graphite, finite mono-layer graphene and 3-layer graphene agree well with previous experiments. The dimensional transitions of the intrinsic k and the extent of the diffusive transport regime from mono-layer graphene to graphite are presented. We find a peak enhancement of intrinsic k for multi-layer graphene and graphite with increasing strain and the largest enhancement amplitude is about 40%. In contrast the calculated intrinsic k with tensile strain decreases for diamond and diverges for graphene, we show that the competition between the decreased mode heat capacities and the increased lifetimes of flexural phonons with increasing strain contribute to this k behavior. Similar k behavior is observed for 2-layer hexagonal boron nitride systems, suggesting that it is an inherent thermal transport property in multi-layer systems assembled of purely two dimensional atomic layers. This study provides insights into engineering k of multi-layer graphene and boron nitride by strain and into the nature of thermal transport in quasi-two-dimensional and highly anisotropic systems.
