Nickel Carbide as a Source of Grain Rotation in Epitaxial Graphene

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• 作者：Peter Jacobson ; Bernhard St枚ger ; Andreas Garhofer ; Gareth S. Parkinson ; Michael Schmid ; Roman Caudillo ; Florian Mittendorfer ; Josef Redinger ; Ulrike Diebold
• 刊名：ACS Nano
• 出版年：2012
• 出版时间：April 24, 2012
• 年：2012
• 卷：6
• 期：4
• 页码：3564-3572
• 全文大小：587K
• 年卷期：v.6,no.4(April 24, 2012)
• ISSN：1936-086X

文摘

Graphene has a close lattice match to the Ni(111) surface, resulting in a preference for 1 脳 1 configurations. We have investigated graphene grown by chemical vapor deposition (CVD) on the nickel carbide (Ni₂C) reconstruction of Ni(111) with scanning tunneling microscopy (STM). The presence of excess carbon, in the form of Ni₂C, prevents graphene from adopting the preferred 1 脳 1 configuration and leads to grain rotation. STM measurements show that residual Ni₂C domains are present under rotated graphene. Nickel vacancy islands are observed at the periphery of rotated grains and indicate Ni₂C dissolution after graphene growth. Density functional theory (DFT) calculations predict a very weak (van der Waals type) interaction of graphene with the underlying Ni₂C, which should facilitate a phase separation of the carbide into metal-supported graphene. These results demonstrate that surface phases such as Ni₂C can play a major role in the quality of epitaxial graphene.

Keywords:

chemical vapor deposition; polycrystalline graphene; STM; DFT; grain boundary; nickel