Ab initio thermodynamics and molecular dynamics simulations of graphene growth on liquid Cu

Mie Andersen, Juan Santiago Cingolani and Karsten Reuter

Chair of Theoretical Chemistry, Technical University of Munich, Germany

Abstract

It has been shown that high quality single layer graphene can be obtained through chemical vapor deposition (CVD) on liquid Cu [1]. The role of the liquid surface in graphene nucleation and growth as well as in defect healing is not yet well understood, and the role of hydrogen is still debated [2]. We performed a series of density functional theory calculations of hydrocarbon clusters of different sizes adsorbed to different Cu facets and applied the hindered translator and rotator model [3] for thermodynamic corrections. This allows us to identify the stable precursor molecules at various experimental growth conditions (temperature and partial pressures of gas phase molecules) and various scenarios for the structural motives present at solid and liquid Cu surfaces. At the temperatures relevant for liquid Cu CVD, we find that all precursor molecules will have completely dehydrogenated.

In order to account also for the dynamic nature of the liquid Cu catalyst, we performed molecular dynamics simulations of larger graphene flakes of various sizes on a liquid Cu surface at the level of a variable-charge reactive force field. We find that the graphene flake significantly influences properties of the underlying liquid substrate (mean square displacement, velocity auto-correlation function) and induces a long-range perturbation to the Cu surface density. This could have important implications for the experimentally observed micrometer-range self-alignment of graphene flakes on liquid Cu [4].

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[2] X. Zhang, L. Wang, J. Xin, B.I. Yakobson, F. Ding, J. Am. Chem. Soc. 136, 3040 (2014).

[3] L.H. Sprowl, C.T. Campbell, L. Árnadóttir, J. Phys. Chem. C 120, 9719 (2016).

[4] M. Zeng, L. Wang, J. Liu, T. Zhang, H. Xue, Y. Xiao, Z. Qin, L. Fu, J. Am. Chem. Soc. 138, 7812 (2016).