堆栈有序少层石墨烯单晶体的可控性制备及其光电属性研究

The controlled growth of few layer graphene (FLG) is an important topic which aims either to increase the domain size and thickness uniformity or to control the number of layers and stacking order of FLG. The chemical vapour deposition(CVD) on nickel(Ni) substrate was frequently used in the fabrication of FLG and multi-layer graphene. However, graphene made by the traditional CVD method suffers from drawbacks like poor thickness uniformity and small grain size. The depression of carbon dissovability in Ni substrate is a key factor for the controllable growth of FLG. In this study, the traditional CVD method was modified and imporved by introducing oxygen impurity in the CVD chamber. With the assistance of oxygen impurity, the controllable growth of FLG can be achieved by a combination of depression of carbon dissolvability and etching by hydrogen. The topics of this study includes, (1) the growth dynamics and controllable fabrication of FLG; (2) the mechanism of oxygen impurity in the growth process of graphene; (3)the ways to modify the stacking order of FLG and the mechanism behind; (4)study on the opto-electric properties of FLG and its application in fields like organic photovolatic devices and nano-optoelectric devices. We intend to discover the unknown factors which influence the growth of graphene, and to achieve a controllable fabrication of FLG with at least millimeter grain size and order stacking. The bottleneck problem in graphene fabrication is expected to be overcomed in this study, which enhances the importance of this study in the sense of science and technology.

少层石墨烯（FLG）的可控性生长是石墨烯研究的重点。提高单晶颗粒尺度和厚度均一性、调控层间堆叠结构是FLG制备研究的主要目标。以多晶镍为基底利用化学气相沉积法（CVD）可实现少层及多层石墨烯的制备。然而，利用传统CVD方法制备的石墨烯存在厚度不均、晶粒小等瓶颈问题。解决上述问题的关键在于对渗碳的抑制。本课题提出有氧环境下的CVD制备新方法，拟以"杂质"氧为调控要素，采用底层抑制渗碳与顶层刻蚀多层石墨烯相结合的方法，调控石墨烯的生长行为。研究内容：（1）FLG的可控性生长及其生长动力学行为；（2）氧在石墨烯CVD生长过程中的作用机制；（3）FLG堆栈结构的调控机制；（4）FLG的光电属性及其在有机光伏、纳米光电子器件等领域的应用。本研究将揭示少层石墨烯生长中的未知机制，实现具有毫米级晶粒尺寸且堆栈有序的少层石墨烯的可控性制备。本课题有望突破石墨烯制备的瓶颈问题，因而具有较高学术和应用价值。

制备大尺寸、无缺陷的石墨烯单晶是实现石墨烯材料在半导体领域工业应用的前提。为此，需掌握影响石墨烯化学气相沉积生长的关键参数，认识单晶石墨烯生长的动力学行为，揭示关键物理机制。本课题专注与石墨烯的化学气相沉积生长研究。本课题研究了CVD气氛环境中的微氧组分对单晶石墨烯生长的影响，并通过调控CVD气氛中氧气的偏压，实现了毫米级单层石墨烯的可控制备。课题深入研究了石墨烯CVD沉积机制，发现了一种由边界结构特点决定的增原子聚集机制，在这种机制驱使下，石墨烯单晶晶畴的前端保持将保持特定的边界结构，这种生长机制避免了边界上枝状分形的形成。课题还提出了一种铜箔退火处理方法。以这种退火方案为前提，实现了大尺寸的双层石墨烯单晶的制备，双层石墨烯具有AB堆栈结构，且其尺寸可达200微米。