Graphene layers on bimetallic Ni/Cu(111) surface and near surface alloys in controlled growth of graphene

Abstract

Bimetallic alloy is more effective than pure metal for controlled growth of high-quality graphene. In this work, we used the DFT-D2 method to study interfacial structure, interaction between graphene layers and bimetallic Ni/Cu(111) surface and near-surface alloys (SAs, NSAs). The results show that the bimetallic Ni/Cu(111) SAs and NSAs have a larger surface relaxation and charge transfer at the interface. The Ni/Cu(111) SAs/NSAs with a Cu-surface layer are energetically more favorable than that with a Ni-surface layer. However, the Ni-surface layer of the Ni/Cu(111) SAs/NSAs has more charge accumulation and higher chemical activity than the Cu-surface layer of the Ni/Cu(111) SAs/NSAs. More importantly, the interaction strength of graphene–metal can be distinctly tuned by surface alloying, while it has only a minor change by subsurface alloying. The initially weak interfacial interaction of graphene/Cu(111) could be enhanced substantially by Ni surface introduction. Accordingly, the interface distance was decreased from ∼3.0 Å to ∼2.1 Å, and there is a strong charge transfer from the Ni-surface layer to the graphene bottom layer. In contrast, the initially strong interfacial interaction of graphene/Ni(111) could be reduced successfully by Cu surface introduction. The interface distance was increased from ∼2.1 Å to ∼3.0 Å, and there is only a minor electronic polarization at the interface between graphene and Ni(111)–Ni–Cu SA. Furthermore, the graphene bottom layer on the Ni-surface layer of the Ni/Cu(111) SA/NSAs has higher chemical activity than that on the Cu-surface layer of the Ni/Cu(111) SA/NSAs. These findings provide a useful guide for designing alloy catalysts and achieving controlled growth of graphene.