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Chemistry vs geometry: the role of the substrate on epitaxial graphene

Ina a combined experimental and theoretical work we have demonstrated that the chemical composition of the substrate's topmost atomic layer plays a major role in determining the coupling between epitaxial graphene and its metal substrate.

F. Presel et al., Carbon 93, 187 (2015).
The coupling of graphene with metallic surfaces is an important topic in contemporary materials science, due to its potential impact on a number of high-performance electronic applications. In particular, such applications require graphene to be efficiently coupled to metallic contacts. This can be achieved by growing it directly on top of metallic surfaces via Chemical Vapour Deposition. The interaction of graphene with metal surfaces, however, causes modifications to the electronic properties of the former: a detailed understanding of the interactions occurring at interfaces between graphene and metals is therefore required to create and tailor the properties of high-performance graphene-based nanoelectronic devices.

We have performed a combined experimental and theoretical work in order to separate the contributions to the interaction strength between epitaxial graphene and transition metal surfaces arising from the geometrical and chemical properties of the supporting surfaces.

This has been achieved by performing high energy resolution photoelectron measurements and numerical simulations of the C1s core level spectral distribution for a large number of graphene-metal interfaces, which have been obtained by systematic intercalation of different metals (Co, Rh, Ir and Ru) at the graphene-Ir(111) and graphene-Ru(0001) interfaces.

We have demonstrated that the chemical species of the substrate's topmost layer plays a major role in determining the coupling between graphene and its substrate. Moreover, we have showed that both the experimental and the theoretical C1s spectral centres of mass are in linear relationship with the d-band centre of the transition metal substrate, which is considered a reliable descriptor of the graphene-substrate interaction strength and demonstrates the applicability of Hammer and Nørskov's model for the chemisorption of molecules on transition metal surfaces also to the graphene/metal systems. 

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Unravelling the roles of surface chemical composition and geometry for the graphene-metal interaction through C1s core-level spectroscopy

F. Presel, N. Jabeen, M. Pozzo,  D. Curcio, L. Omicuolo, P. Lacovig, S. Lizzit, D. Alfè and A. Baraldi.
Carbon 93, 187 (2015).
Last Updated on Tuesday, 26 November 2019 20:26