石墨烯表面金属纳米材料生长形貌以及生长机制的探索

The discovery of graphene offers a prototype model for studying the nature of two-dimensional systems at the electronic and atomic levels and provides a fertile ground for applications. In addition to the fascinating intrinsic electronic and mechanical properties exhibited by pure graphene, the structure and properties of graphene can also be controlled and modified by adsorption and doping atoms and molecules on graphene layer. The materials based on graphene can broaden the range of applications from nanoscale devices, catalysis, spintronics, to nanomagnetic devices etc. This project based on metals on graphene, will be mainly focus on the further studies of metals adsorption on graphene, interaction between adatoms, and growth morphology etc, by using first-principles calculations and Kinetic Monte Carlo (KMC) simulations. The purpose of this proposal is to investigate the interaction between metals and graphene, and to explore the nature of bonding, by analysis of adsorption energetics, properties, and thermal stabilities for metals nano-materials on graphene. On the other hand, this work scheme is aiming at revealing the characters and origins of different interactions as well as studying the correlation between adsorption properties and growth morphology by first-principles calculations and Kinetic Monte Carlo (KMC) simulations combined with experiment in close collaboration. The results of this research project can serve as a basis for future experimental and theoretical studies of adsorption on graphene.

石墨烯不仅具有独特的电子结构和新颖的力学特征，还可通过吸附或掺杂原子来对其电子结构和性质进行修饰及调控，因而在纳米器件、表面催化、磁性存储、自旋过滤等方面具有广泛的应用。本项目拟利用第一性原理计算和动力学蒙特卡罗模拟，对金属纳米微粒在石墨烯及缺陷石墨烯表面的吸附行为进行理论模拟研究。重点研究内容为：首先对金属纳米微粒吸附进行研究，确定金属纳米微粒与石墨烯之间的成键作用和微观成键本质；其次对金属原子间相互作用进行分类，揭示相互作用的特征及产生根源；最后利用动力学蒙特卡罗模拟对不同类型金属在石墨烯表面生长形貌的演化过程进行探索，分析不同类型金属生长形貌差异的本质区别。同时结合实验，建立金属生长形貌和以石墨烯为碳质的金属纳米材料性质之间的关联。本项目的理论模拟研究可为实验上合成和改进具有新颖性能的石墨烯表面金属纳米材料提供可靠的理论指导，具有重要的科学意义和实用价值。

石墨烯具有优异的电学性能、出众的热导率以及卓越的力学性能，拥有广阔的应用前景。本项目利用第一性原理计算对金属纳米微粒在石墨烯表面的吸附、相互作用、吸附性质与生长形貌之间的关联以及生长机制进行理论模拟研究。我们发现(1)过渡金属纳米微粒与石墨烯衬底之间相互作用很强，定量QUAMBOs (quasi-atomic minimal basis set orbitals approach)分析表明为共价相互作用。与气相金属纳米微粒相比，其在石墨烯表面吸附会使得体系磁矩增加，这要归因于金属原子和碳原子之间相互作用导致电荷重新分布和电荷转移。过渡金属的引入可使材料获得可调的磁性。(2)碱金属在石墨烯表面的相互作用为长程屏蔽库伦相互作用。这种长程相互作用对理解碱金属在石墨烯表面生长的结构相变、石墨烯表面金属纳米材料自组装控制以及石墨烯表面电子屏蔽机制起到了很重要的作用。(3)生长形貌不仅与由扩散能垒、金属在石墨烯表面吸附能与在其体内的内聚能的比值(Ea/Ec)有关,同时还与金属在石墨烯表面吸附所诱导的性质有关。吸附诱导的相互作用包括，间接相互作用(或RKKY)、偶极-偶极相互作用、弹性相互作用等，也同样对金属纳米材料在石墨烯表面的生长形貌起到了很重要的作用。本研究建立了金属生长形貌和纳米材料性质之间的关联。