石墨烯在氮化硼衬底及相关二维复合结构中热传导的理论研究

Graphene is composed of monolayer carbon atoms arranged in the honeycomb lattice. Its intrinsic thermal conductivity at room temperature is found in experiment to exceed 3000 W/m-K, which can have promising applications in the thermal management of the electronic devices. Thus thermal properties of graphene have attracted much attention recently. In practical applications, graphene needs to be in contact with other materials, such as the substrate. Experimental study reports the thermal conductivity of supported graphene on amorphous silicon dioxide substrate is only about 600 W/m-K at room temperature, which greatly limits the utilization of the intrinsically high thermal conductivity of graphene. In this project, we will use hexagonal boron nitride (h-BN), which has the similar lattice structure as graphene, as the substrate, and explore the thermal transport properties of graphene on crystalline substrate and the underlying physical mechanism. Our study may have potential applications in the thermal management of nanoelectronic devices, and the design of high-performance thermal interface materials. On the other hand, due to the recent advance in the synthesis of two-dimensional (2D) materials, the stacking of different 2D materials at atomic level has been recently realized in experiment, i.e., van der Waals heterostructures. We will systematically study the novel thermal transport properties of van der Waals heterostructures composed of graphene, h-BN, and other related 2D materials. In order to provide a deep understanding of the experimental measurement data for the thermal conductivity value of supported graphene on substate, we will simulate many realistic factors existing in experiment, such as vacancy defects, chemical residues, interfacial strain and so on, and study their effects on graphene thermal conductivity. Furthermore, we will explore the physical mechanisms for controlling the lattice vibration by multiple designing factors in the heterostructures, such as lattice arrangement, periodic length, material components and so on, and their corresponding impacts on thermal transport will be investigated. This project seeks to discover the basic principles that govern the heat conduction in van der Waals heterostructures, and provide theoretical guidance to the experimental studies for controlling the thermal properties of such 2D heterostructures.

石墨烯是由单层碳原子按蜂窝结构排列而成, 实验发现其室温本征热导率大于3000W/m-K。这使石墨烯在电子器件热控制方面具有很好的应用前景，近年来引起了人们的大量关注。在实际应用中，石墨烯需要与衬底或其他材料接触，实验研究发现室温下石墨烯在非晶体衬底二氧化硅上的热导率仅为600W/m-K, 极大地限制了人们利用石墨烯极高的本征热导率。本项目将采用与石墨烯具有相似晶格结构的六方氮化硼作为衬底，研究石墨烯在晶体衬底上的热输运性质及相关物理机制，为微纳电子器件的热控制以及高性能导热界面材料的设计提供可能的解决方案。另一方面，由于二维材料制备技术的最新进展，人们最近已制备出不同二维材料在原子层面的堆积，即二维复合结构。本项目将系统地研究石墨烯、氮化硼及其相关二维复合结构中新异的热输运性质，通过模拟实验中多种实际因素对石墨烯热导率的影响，例如空位缺陷、化学残留和界面应力等，深入理解实验工作中测得的石墨烯在衬底上的热导率；讨论复合结构中不同排列方式、周期长度及材料组分等因素调控晶格振动的物理机制及其对热导率的影响，探讨二维复合结构中热传导的基本规律，为实验中利用二维复合结构调控热传导提供理论指导。

本项目围绕石墨烯在氮化硼衬底及相关复合结构中热传导问题，开展了系统的理论研究。核心目标是通过理论模拟和分析，研究石墨烯在晶体衬底（以氮化硼为例）上的热输运性质和机理，为实验中选择合适衬底材料以提高衬底上石墨烯热传导性能提供理论指导。此外，其他目标包括揭示缺陷调控石墨烯热导率的机理，以及探索与石墨烯相关复合结构中的热输运性质。本项目按照上述研究目标系统并深入地开展了相关科学问题的研究，揭示了石墨烯在氮化硼衬底及相关复合结构中热输运调控机理和关键参量设计。项目研究成果为相关实验工作和应用提供了重要科学基础。