Thermal properties of graphene and graphene-based thermal diodes

In the perspective of manipulating and controlling heat fluxes, graphene represents a promising material revealing an unusually high thermal conductivity �. However, both experimental and theoretical previous works lack of a strict thermal conductivity value, estimating results in the range 89-5000 W m-1 K-1. In this scenario, I address graphene thermal transport properties by means of molecular dynamics simulations using the novel "approach to equilibrium molecular dynamics" (AEMD) technique. The first issue is to offer some insight on the active debate about graphene thermal conductivity extrapolation for infinite sample. To this aim, I perform unbiased (i.e. with no a priori guess) direct atomistic simulations aimed at estimating thermal conductivity in samples with increasing size up to the unprecedented value of 0.1 mm. The results provide evidence that thermal conductivity in graphene is definitely upper limited, in samples long enough to allow a diffusive transport regime for both single and collective phonon excitations. Another important issue is to characterize at atomistic level the experimental techniques used to estimate graphene thermal conductivity. Some of these use laser source to provide heat. For these reasons, I deal with the characterization of the transient response to a pulsed laser focused on a circular graphene sample. In order to reproduce the laser effect on the sample, the K - A01 and