石墨烯化学气相沉积生长中氧的作用机制

Graphene is the new basic material with outstanding electrical, optical, thermal and mechanical properties. The reliable synthesis of high-quality graphene with scalable sizes is a prerequisite for fulfilling the potential use of graphene in various applications. Although extensive research has been performed to elucidate the basic growth mechanisms of graphene, the underlying mechanisms are far from being understood. The latest but very limited studies show oxygen influences graphene growth. However, the details remain to be uncovered. Here, on the basis of our recent study, we will study the function of oxygen on graphene growth on Cu and Cu-Ni alloy by chemical vapor deposition (CVD). We will systematically investigate the graphene growth as a function of oxygen content and distribution in the metal substrates or oxygen gas in the CVD system, and evaluate the electronic and optical performances of the graphene grown with/without oxygen involved in the synthesis. Based on our experimental results, we aim to elucidate the underlying mechanisms of oxygen functionaliztion on graphene growth, establish the growth model of graphene with oxygen involvement, and provide appropriate protocols of graphene fabrication by the first-principles calculation. The purpose of using the conventional but important Cu and Cu-Ni alloy substrates for graphene synthesis is to establish the key technologies for the producing of graphene films with fine control over the number of graphene layers, towards practical applications of graphene in electronics, optics, information technologies, new energy, aerospace and biomedicine.

石墨烯是在光、电、热、力等方面具有优异性能，极具应用潜力、可广泛服务于经济社会发展的新材料。其应用的前提是其规模化可控制备，然而可控制备依旧是个巨大挑战；最近有限的研究表明氧影响石墨烯的生长，但缺乏系统详尽的研究。在申请人前期的研究基础上，本项目研究氧对在铜和铜镍合金基底上石墨烯化学气相沉积生长的作用机制。将重点通过调节基底中氧的含量和分布以及制备系统中氧气分压系统调查氧对石墨烯生长的影响，进而揭示其作用规律；评估有（无）氧条件下生长的石墨烯薄膜的质量。以实验结果为基础，借助第一性原理计算揭示氧的作用机制，建立有氧参与下的石墨烯生长的理论模型，指导石墨烯的制备。通过本项目研究，揭示氧对石墨烯成核和成膜的可控制备的内在作用规律，选用常用且重要的铜和铜镍基底，以便建立有氧条件下石墨烯薄膜层数可控的关键技术，为石墨烯在信息光电子、新能源、航空航天、生物医学等领域实际应用奠定基础。

石墨烯是在光、电、热、力等方面具有优异性能，极具应用潜力、可广泛服务于经济社会发展的新材料。为了揭示氧对石墨烯成核与生长的影响，本项目展开了相关的研究。实验和理论相结合研究了铜箔表面氧、微纳结构（Cu hill）等对石墨烯成核与生长的影响，发现石墨烯成核的优先顺序为富氧的具有Cu hill的衬底、富氧的铜衬底、Cu hill、平的铜衬底，氧的存在能够大大提高衬底对C的结合能，相应的结合能变化规律为16.603 eV，11.257 eV，7.806 eV至7.067 eV；结合能越大意味石墨烯成核越容易。以上研究为石墨烯的可控制备提供了基础（Nanoscale 9, 3719 (2017); Carbon 147, 120 (2019); Rep. Prog. Phys. 81, 036501 (2018)）。研究了气体（氧）穿越石墨烯涟漪（ripple），发现石墨烯中的涟漪是氧渗透石墨烯薄膜的通道，密度泛函理论计算表明，涟漪的存在大大地降低了氧原子渗透石墨烯的能量势垒，使得渗透成为可能（2D Mater. 4, 025010 (2017)）；这为设计可透过性石墨烯膜提供研究基础。研制了高性能的基于石墨烯的柔性透明导电膜、实现了柔性太阳能电池（Nanotechnology 28, 305402 (2017), IEEE J. Photovol. 9, 214 (2019)），研制了高性能的石墨烯天线，这展示了石墨烯在不同的光电字产品应用潜力。同时，在本项目的资助下，在二维材料领域展开了其他探索性研究，获得一些原创性成果，比如从0到1制备了具有优异电、磁特性的CrS2材料等 (Nanoscale 11, 20123 (2019))。