Simulation Of The Thermal Properties Of Low-dimensional Carbon/Boron Nitride Hetero-structures

In recent years,integrated circuits have become more and more integrated and have expanded from two-dimensional to three-dimensional structures.On the other hand,high-power integrated circuits are used in large numbers in hotspots such as electric vehicles,solar photovoltaics and smart grids.Therefore,the issue of efficient thermal management of integrated circuits is becoming increasingly important.In nanoscale integrated circuit structures,the original macroscale heat transfer mechanisms are no longer applicable.The research of new theories,materials and devices for thermal management at the nanoscale has become an important task in the field of IC thermal management.Hexagonal boron nitride（Hexagonal Boron Nitride,h-BN）is similar to graphene in that both have a honeycomb mesh structure,close lattice parameters and both have high thermal conductivity.The study of the thermal conductivity of carbon/hexagonal boron nitride hetero-structures has important theoretical and practical implications for their application in the field of thermal management of integrated circuits.In this paper,the following work has been carried out using a molecular dynamics approach with low-dimensional carbon/boron nitride hetero-structures.Firstly,the physical model of the low-dimensional carbon/boron nitride hetero-structures are developed by MATLAB and the simulation models are set up.These include the type of atoms,the coordinates of the atoms,the area of the thermal bath,the boundary and interface configuration of the model,the connection of the interfaces and the content and format of the input files,enabling the automatic generation of specific simulation input files.Secondly,the thermal properties of low-dimensional graphene/boron nitride in-plane hetero-structures are investigated.The Reax FF potential function is applied to calculate the 1D/2D carbon/boron nitride in-plane hetero-structures for the first time,and we obtain the corresponding interfacial thermal conductivity,interfacial thermal resistance and thermal rectification ratio.The interfacial thermal conductivity is in the order of 10¹⁰-10¹¹Wm^-2K^-1 and the interfacial thermal resistance is in the order of 10^-11-10^-10K m ²W^-1.In the simulations,heat flow is applied in the forward and backward directions along the length of the model using the r-NEMD method.The results show that:1.the heat flow preferentially flows from the BN atomic region to the C atomic region.2.there is a difference in the interfacial thermal conductivity/interfacial thermal resistance in both directions,i.e.a thermal rectification effect is found at the interface.3.the magnitude of the thermal rectification ratio expands with increasing unity length.In addition,the effect of system temperature and structure ratio on the thermal rectification ratio of the heterogeneous structure within the 2D graphene/boron nitride surface is also investigated.It is found that a higher temperature and a smaller percentage of graphene regions lead to a larger thermal rectification ratio.Thirdly,the mechanism of phonon thermal transport at the interface is explained using the phonon density of states（PDOS）and cumulative correlation factor（CCF）methods.It is found that the thermal rectification phenomenon（differences in interfacial thermal conductivity/interfacial thermal resistance in different heat flow directions）arises due to the matching/mismatched vibrational modes of the out-of-plane phonons at the interface in the two heat flow directions.The thermal rectification ratios obtained in this paper are 286.7%in the 1D hetero-structure and 117.9%in the 2D hetero-structure when the simulated system length is up to 150 nm.In summary,this paper investigates the thermal conductivity of low-dimensional carbon/boron nitride hetero-structures based on the Reax FF potential function using a non-equilibrium molecular dynamics approach,and elucidates the mechanism of the thermal rectification phenomenon from the perspective of phonon dynamics,providing theoretical guidance for its application in the field of thermal management of integrated circuits.