碳化硅纳米颗粒表面石墨烯量子点生长机制与形貌调控的理论研究

The research of graphene is always given to attention in recent years. Because of its unique physical properties, graphene have great potential applications in many fields, such as optics, electricity, magnetics, mechanics and biology. With decreasing its size, graphene exhibits unique quantum confinement and edge effects, given rise to some new physical properties. However, it is difficult to prepare the nanoscale graphene sheets, which limits its applications in area of semiconductor quantum dot materials. Although graphene quantum dots (GQD) can be obtained by cutting graphene sheets, direct growth of GQD is a difficult question in material science. In this project, a kinetic growth process of grpahene on surface of Silicon Carbide (SiC) nanoparticles is investigated using the molecular dynamics simulations and the first principle calculation. The intrinsic relation among the five kinds of dynamical behaviors, which are adatom diffusing, adatom desorption, nucleation of graphene, growth of graphene and microstructure evolution of graphene, is analyzed. A kinetic growth model of graphene on surface of SiC nanoparticles will be established, which can reveal the growth mechanism of graphene. Our research focus on obtaining the optimum growth conditions and preferred orientation of graphene on surface of SiC nanoparticles, and controlling growth size, shape, and thickness of graphene, in order to explore a method of the epitaxial growth of GQD on surface of SiC nanoparticles.

近年来，石墨烯研究备受人们的关注。石墨烯因其具有许多优异的物性，在光、电、磁、力学、生物等领域都有潜在的应用。随着石墨烯尺寸的减小，它表现出独特的量子约束及边界效应，引发了一些新的物理性质。不过，纳米级的石墨烯片难以制备，这限制了它应用于"量子点"这一半导体组件的前景。虽然经过精细加工可以将石墨烯片切割成各种形状的量子点，但石墨烯量子点的大规模直接生长一直是材料学研究的难题之一。本项目将利用第一性原理计算与分子动力学模拟方法系统研究碳化硅纳米颗粒表面石墨烯生长的动力学过程，分析碳化硅颗粒表面原子的扩散、解附等行为与石墨烯的成核、生长，以及形貌演变之间的内在关联，建立纳米颗粒表面石墨烯生长的微观物理模型，揭示其生长机制；并通过模拟获取纳米颗粒表面石墨烯的最佳生长条件、生长取向，精确调控石墨烯生长尺寸、形状及厚度，探索碳化硅纳米颗粒表面直接外延生长石墨烯量子点的方法。

石墨烯因其具有许多优异的物性，在光、电、磁、力学、生物等领域都有潜在的应用。不过，纳米级尺寸的单原子层石墨烯片难以制备，这限制了它应用于"量子点"这一半导体组件的前景。石墨烯量子点的大规模直接生长是目前材料学研究的重要课题之一。本项目利用第一性原理计算与分子动力学模拟方法系统研究碳化硅纳米颗粒表面石墨烯生长的动力学过程，分析碳化硅表面原子的扩散、解附等行为与石墨烯的成核、生长，以及形貌演变之间的内在关联，揭示其生长机制；并研究碳化硅表面石墨烯生长及其形貌的调控机制，为探索碳化硅表面直接外延生长石墨烯量子点的方法提供理论基础。研究发现，6H-SiC(000-1)表面碳原子的解附行为明显强于(0001)表面；发现SiC表面碳空位缺陷将极大促进碳化硅表面硅原子的解离；研究还发现，6H-SiC(000-1)表面同时存在碳空位和硅空位时，碳原子的吸附能力显著增强而硅原子的吸附能力显著减弱，说明这种表面缺陷情况最有利于石墨烯的成核生长。采用经典分子动力学方法分别模拟了6H-SiC 表面硅原子的蒸发和碳原子的自组织过程；并从原子尺度展现了SiC表面和Si晶体表面单原子层和双原子层石墨烯的周期性褶皱形貌，发现石墨烯结构与基底晶体表面原子的晶格失配是产生石墨烯褶皱形貌的重要原因。这些研究结果有助于人们进一步认识和理解SiC表面石墨烯生长初期的成核与生长机制，以及SiC表面石墨烯结构形貌的调控，为探索SiC外延生长石墨烯量子点的方法提供理论参考。