The Parameter Space of Graphene Chemical Vapor Deposition on Polycrystalline Cu
The Parameter Space of Graphene Chemical Vapor Deposition on Polycrystalline Cu
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DOI：
10.1021/jp303597m
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发表时间：
2012-10-25
影响因子：
3.7
通讯作者：
Hofmann, Stephan
中科院分区：
文献类型：
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作者：
Kidambi, Piran R.;Ducati, Caterina;Hofmann, Stephan
对多晶铜箔上石墨烯化学气相沉积 (CVD) 的参数空间进行了系统研究，旨在获得更基本的工艺原理，特别是关于碳前驱体的选择和铜升华的缓解。 CH4 作为前驱体需要 H-2 稀释和温度 >= 1000 摄氏度，以保持铜表面还原并产生高质量、完整的单层石墨烯覆盖。 H-2 气氛蚀刻生长的石墨烯；因此，保持平衡的 CH4/H-2 比例至关重要。这种平衡在低压条件下更容易实现，但在低压条件下铜的升华达到有害水平。相比之下，C6H6 作为前体不需要反应性稀释剂，并且在 100-150 摄氏度的较低温度下始终能提供类似的石墨烯质量。更低的工艺温度和更稳健的工艺条件可以有效解决铜升华问题。对于任何前体来说，石墨烯的形成本质上并不局限于单层。相反，提供的碳化学势越高，薄膜不均匀性以及初级和次级多层石墨烯成核的可能性就越高。对于后者，固有多晶 CVD 石墨烯的域边界为催化剂提供了持续碳供应的途径。石墨烯的形成受到铜晶体学的显着影响；也就是说，催化剂模板的微观结构和织构的演变是 CVD 过程的一个组成部分。
A systematic study of the parameter space of graphene chemical vapor deposition (CVD) on polycrystalline Cu foils is presented, aiming at a more fundamental process rationale in particular regarding the choice of carbon precursor and mitigation of Cu sublimation. CH4 as precursor requires H-2 dilution and temperatures >= 1000 degrees C to keep the Cu surface reduced and yield a high quality, complete monolayer graphene coverage. The H-2 atmosphere etches as grown graphene; hence, maintaining a balanced CH4/H-2 ratio is critical. Such balance is more easily achieved at low-pressure conditions, at which however Cu sublimation reaches deleterious levels. In contrast, C6H6 as precursor requires no reactive diluent and consistently gives similar graphene quality at 100-150 degrees C lower temperatures. The lower process temperature and more robust processing conditions allow the problem of Cu sublimation to be effectively addressed. Graphene formation is not inherently self limited to a monolayer for any of the precursors. Rather, the higher the supplied carbon chemical potential, the higher the likelihood of film inhomogeneity and primary and secondary multilayer graphene nucleation. For the latter, domain boundaries of the inherently polycrystalline CVD graphene offer pathways for a continued carbon supply to the catalyst. Graphene formation is significantly affected by the Cu crystallography; i.e., the evolution of microstructure and texture of the catalyst template form an integral part of the CVD process.