In Situ Observations of the Atomistic Mechanisms of Ni Catalyzed Low Temperature Graphene Growth
In Situ Observations of the Atomistic Mechanisms of Ni Catalyzed Low Temperature Graphene Growth
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DOI：
10.1021/nn402927q
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发表时间：
2013-09-01
期刊：
影响因子：
17.1
通讯作者：
Cepek, Cinzia
中科院分区：
文献类型：
--
作者：
Patera, Laerte L.;Africh, Cristina;Cepek, Cinzia
通过互补的原位扫描隧道显微镜和X射线光电子能谱直接揭示了在低于600℃的技术相关碳氢化合物暴露下，在镍表面形成石墨烯的关键原子机制。对于低于500℃的清洁的Ni(111)晶面，两种不同的表面碳化物(Ni2C)转化机制占主导地位，这两种转化机制都产生了外延石墨烯，而在500℃以上，石墨烯主要通过导致嵌入的外延和/或旋转的石墨烯结构域的置换机制直接生长在Ni(111)上。冷却后，额外的碳结构仅在旋转的石墨烯结构域下形成。主要的石墨烯生长机制还严重依赖于近表面的碳浓度，因此与催化剂的完整历史和所有可能的污染源密切相关。这些过程的详细XPS指纹可以直接链接到对各种生长条件的高压XPS测量，包括石墨烯和碳纳米管CVD工业反应堆中常用的多晶镍催化剂和配方。这使得能够对以前的文献进行明确和一致的解释，并评估生长的碳纳米结构的质量/结构与生长模式的关系。
The key atomistic mechanisms of graphene formation on Ni for technologically relevant hydrocarbon exposures below 600 degrees C are directly revealed via complementary in situ scanning tunneling microscopy and X-ray photoelectron spectroscopy. For clean Ni(111) below 500 degrees C, two different surface carbide (Ni2C) conversion mechanisms are dominant which both yield epitaxial graphene, whereas above 500 degrees C, graphene predominantly grows directly on Ni(111) via replacement mechanisms leading to embedded epitaxial and/or rotated graphene domains. Upon cooling, additional carbon structures form exclusively underneath rotated graphene domains. The dominant graphene growth mechanism also critically depends on the near-surface carbon concentration and hence is intimately linked to the full history of the catalyst and all possible sources of contamination. The detailed XPS fingerprinting of these processes allows a direct link to high pressure XPS measurements of a wide range of growth conditions, including polycrystalline NI catalysts and recipes commonly used In Industrial reactors for graphene and carbon nanotube CVD. This enables an unambiguous and consistent interpretation of prior literature and an assessment of how the quality/structure of as-grown carbon nanostructures relates to the growth modes.