Thermal rectification effect of pristine graphene induced by vdW heterojunction substrate.

As an effective means of thermal management, thermal rectification (TR) has been studied in a variety of complex asymmetric or heterogeneous structures. Due to experimental conditions, many complex structures cannot be realized easily, and the low-temperature thermal bath temperature far below room temperature does not conform to the actual application environment of the device. In this paper, we studied the thermal rectification inside graphene supported by a heterogeneous substrate of SiO 2 and GaN alternately. Heat flux is easier to transfer from the graphene covered on the SiO 2 side to the GaN side. When the temperature of the cold bath is maintained at 300 K, only the temperature of the high-temperature hot bath is changed, and the maximum TR rate is about 52%. TR rate can be tuned by heat source temperature and size, with heat source size of 2 nm and temperature above 450 K, the highest TR rate can be obtained. The phonon density of states and participation ratio reveal the influence of the substrate and position on the phonon transport in graphene. Besides, the spectral energy density analysis confirmed that the substrate effect caused the shift of the graphene flexural phonon mode and the reconstruction of the phonon spectrum, which was in good agreement with PDOS, and further explain the basic mechanism of TR from the scattering rate and the degree of localization. [Display omitted] The thermal rectification effect of graphene covered on a heterojunction substrate composed of SiO 2 and GaN was studied by using non-equilibrium molecular dynamics (NEMD). The interface thermal resistance between the thermal bath and central area also needs to be considered, at high temperature, the whole system cannot reach the ideal thermal rectification rate. Moreover, the phonon participation ratio and spectral energy density are calculated to understand the mechanism of thermal rectification and the physical nature of the substrate effect, respectively. • Propose a non-destructive thermal rectification method for the pristine graphene. • Thermal rectification effect of the graphene system at high temperature is studied. • The non-linear interface thermal resistance between thermal bath and central area is considered. • Phonon participation ratio proves the localization characteristics of different positions. • SED analysis proves the drift and reconstruction of graphene phonon spectrum under substrate effect. [ABSTRACT FROM AUTHOR]