| AVS 62nd International Symposium & Exhibition | |
| In-Situ Spectroscopy and Microscopy Focus Topic | Monday Sessions |
| Session IS+AS+SS-MoM |
| Session: | Fundamental Studies of Surface Chemistry of Single Crystal and Nanomaterials under Reaction Conditions |
| Presenter: | Robert Weatherup, Lawrence Berkeley National Laboratory |
| Correspondent: | Click to Email |
Critical to controlling the growth of graphene and carbon nanotubes during chemical vapor deposition (CVD) is a detailed understanding of the role of the catalyst, however this remains incomplete due the wide parameter space. Here we investigate the dynamics of graphene-catalyst interactions during CVD using time- and depth-resolved X-ray photoelectron spectroscopy[1-2], in situ scanning tunneling microscopy,[3] and grand canonical Monte Carlo simulations coupled to a tight-binding model[1]. We focus on Ni(111) as a model catalyst surface and probe in-operando a wide range of hydrocarbon exposure pressures (10-6-10-1 mbar). The key atomistic mechanisms of graphene formation on Ni are thereby revealed and our data highlights an interdependency between the distribution of carbon close to the catalyst surface and the strength of the graphene-catalyst interaction.
The strong interaction of epitaxial graphene with Ni(111) causes a depletion of dissolved carbon close to the catalyst surface, which prevents additional layer formation leading to a self-limiting graphene growth behavior for low exposure pressures (10-6-10-3 mbar). Increasing the hydrocarbon pressure further (to ~10-1 mbar) leads to weakening of the graphene-Ni(111) interaction accompanied by additional graphene layer formation, mediated by an increased concentration of near-surface dissolved carbon. We also reveal that the growth of more weakly adhered, rotated graphene on Ni(111) is linked to an initially higher level of near-surface carbon compared to the case of epitaxial graphene growth. We relate these results to the simple kinetic growth model that we have previously established,[6] and use them to consistently explain previous graphene CVD results in the literature. The key implications for graphene growth control and their relevance to carbon nanotube growth are thereby highlighted.
References
(1) Weatherup et al. J. Am. Chem. Soc. 2014, 136, 13698-13708
(2) Weatherup et al. Nano Lett. 2011, 11, 4154-4160
(3) Patera et al. ACS Nano 2013, 7, 7901-7912
(4) Weatherup et al. ACS Nano 2012, 6, 9996-10003