结构缺陷对双层石墨烯热输运性能的影响机理

Bilayer graphene with unique stacking structure is more advantageous in nanoscale electronics and photonics field than single graphene sheets for its extraordinary physical performance. The bilayer graphene contains many kinds of complicated structure defects in its crystal lattice which make a significant impact on heat transport mechanism. Based on the experiment result, this project will conduct research on the heat transport mechanism of bilayer graphene with structure defects (such as point defects, dislocations and domain walls) using molecular dynamics simulations. The research work includes the following four items: 1. Microtopography of different kinds of structure defects in bilayer graphene are obtained through advanced experimental techniques; 2.The microstructures model and new potential function model adapted to bilayer graphene containing structure defeats are framed; 3.The parallel algorithm is optimized to calculate quantitative thermal conductivities by molecular dynamics simulation which reveal the effects of the key factors of structure defects on heat transport mechanism; 4. Theoretical analysis by the phonon density of states and Boltzmann transport theory are carried out to validate the molecular dynamics simulation results. The research subject of this project is fundamental of the thermal management and thermal design of graphene nanoscale devices, which is important in theory significance and in practical applications.

具有独特堆垛结构的双层石墨烯因出色的物理性能在纳米光电器件领域的应用更优于单层石墨烯。双层石墨烯晶格内部的复杂结构缺陷对其热输运性能会产生重要影响。本项目拟在实验基础上采用分子动力学模拟方法研究含有点缺陷、位错、畴壁等缺陷结构的双层石墨烯的热输运机制。具体研究内容包括：1、通过先进实验手段对双层石墨烯中不同类型结构缺陷的微观形貌进行详细表征；2、准确建立含有复杂缺陷的双层石墨烯微观结构模型及新的势函数模型；3、采用优化的并行算法对双层石墨烯热导率进行分子动力学模拟计算，揭示结构缺陷对其热物性的影响机制；4、利用声子态密度分布以及Boltzmann输运理论对分子动力学模拟结果进行分析与检验。本项目是对石墨烯纳米器件进行热设计和热管理的基础研究，具有重要的理论意义和应用价值。

双层石墨烯具有各种独特的物理性质，如超高的电荷迁移率、优越的导热性和强大的机械强度等，在微纳电子设备、生物传感器、超级电容器等方面具有广阔的应用前景。本项目利用化学气相沉积法成功制备出大面积、高质量双层石墨烯薄膜，采用透射电子显微镜、原子力显微镜、拉曼光谱等方法对得到样品不同类型缺陷的结构特征。由于选用不同势函数对双层石墨烯热导率的计算有不同的结果，我们确定了Kolmogorov-Crespi + REBO势函数对双层石墨烯碳原子之间相互作用的描述较为准确。采用非平衡分子动力学方法研究了双层石墨烯不同类型结构缺陷对其热输运性质的影响。双层石墨烯热导率随缺陷浓度增加而下降，其中空位缺陷对热导率的影响最显著。同时,缺陷结构导致双层石墨烯热导率的尺寸效应和温度依赖关系变弱。通过晶格动力学理论我们计算了双层石墨烯的声子态密度、声子参与率、声子弛豫时间，发现了含有缺陷结构双层石墨烯的热导机理。缺陷结构引起的声子波动性的局域共振杂化和粒子性的散射是造成双层石墨烯热导率明显降低的根本原因。本项目基于结构缺陷对双层石墨烯晶热输运性质的调控，对电子设备热设计和热管理具有很强的科学意义。