石墨烯低温可控制备机理研究

The graphen film, synthesized by chemical vapor deposition (CVD), show great application prospects in touch, display, energy and so on. However, decomposition of gaseous carbon sources usually requires high temperature, typically 1000℃, which is not compatible with the conventional semiconductor process. How the the molecular structure of carbon sources have impact on the temperature of graphene growth and the quality of the derived graphene films and the synthesis mechanism of graphene at low-temperature are not very clear. In this project, we proposed to investigate the controllable synthesis mechanism of graphene at low-temperature by plasma enhancement chemical vapor deposition (PECVD), adopting the aromatic molecules as carbon source. The first principle is used to analyze the dehydrogenation, decomposition, nucleation process of aromatic molecules at low temperature. We further analyze the way of the decomposed active species influence on the synthesized graphene at low-temperature. Besides, it is particularly important to have demonstrate the effect mechanisms of the distribution of plasma power, the proportion of carbon source, the growth pressure on the graphene in PECVD process and explore the relationship between them. Moreover, we further optimize the process parameters during the graphene growth and establish a technology for controllable systhesis graphene at low-temperature, which will provide the theoretical foundation and technique for large-scale produce graphene.

石墨烯具有优异的物理和化学性质，在各个领域具有广泛的应用前景。化学气相沉积（CVD）是制备均匀高质量石墨烯最有前景的方法之一。然而，CVD制备石墨烯通常需要在1000℃左右进行，很难与传统半导体工艺兼容。本课题中，我们拟采用芳香烃结构分子作为有效碳源，与等离子体化学气相沉积技术（PECVD）结合，探索石墨烯低温可控合成与设计该体系的优化条件，着重研究高质量石墨烯低温可控制备机理。通过第一性原理模拟计算，分析芳香烃结构分子在低温制备石墨烯过程中的分解动力学、成核动力学，研究不同芳香烃基团对低温制备石墨烯的影响规律。通过制备方法学研究和工艺设计，探索PECVD工艺中，等离子体能量分布、碳源含量比、生长压强等对石墨烯的影响机制，并对低温合成石墨烯的工艺过程进行优化设计，实现在300℃左右的低温下快速制备高质量石墨烯薄膜。为实现低温下规模化制备高质量石墨烯奠理论基础。

本课题从限域空间石墨烯生长机理入手，首先研究H2在石墨烯制备过程中的作用，阐明了H2并不是石墨烯制备过程中必不可少的控制参数，无氢条件下依然可以制备高品质均匀石墨烯膜；通过研究甲烷裂解的气相反应动力学过程，揭示了CH3•活性基团在限域空间分布非均匀性对石墨烯成核密度、成核大小与生长速度的影响规律；进而利用流体动力学模型对限域空间气体分布均匀性模拟仿真，发现引入多通道气体预混技术能够克服传统CVD进出气方法带来的气流分布不均匀的问题，实现整个CVD管内制备大面积，高质量石墨烯；针对大面积石墨烯单晶可控制备，开发了晶粒“异常长大”基底单晶化快速处理工艺，将工业易于获得的多晶铜箔快速处理成大面积单晶；通过研究石墨烯晶畴外延有序性与基底晶格取向的关系研究，实现了高迁移率石墨烯薄膜的可控制备；经第一性原理模拟计算，分析得到苯作为低温制备石墨烯碳源具有结构简单、旋转对称性、易于制备高品质石墨烯等优点，通过对设备升级改造和对实验的精心设计，着重研究了在限域空间中苯在单晶铜基底上的成核规律，实现了在300℃的低温下石墨烯晶畴有序外延可控生长，并无晶界拼接成大面积单晶。综合上述结果，本研究为限域空间中活性基团分布规律和低温制备石墨烯机理研究奠定了基础。同时为其它二维材料低温制备提供了启示性线索。