Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 108: Graphene: Adsorption, Intercalation and Other Aspects

O 108.4: Talk

Friday, March 24, 2017, 11:15–11:30, TRE Ma

Insight into the wetting of a graphene-mica slit pore with a monolayer of water — •Hu Lin, Andre Schilo, Rauf Kamoka, Nikolai Severin, Igor M. Sokolov, and Jürgen P. Rabe — Department of Physics & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin, Germany

Graphene-mica slit pores are prepared by mechanical exfoliation of graphite onto a freshly cleaved muscovite mica surface in dry nitrogen. We followed their wetting and dewetting with water by scanning force microscopy (SFM) and Raman spectroscopy, which allows to unravel doping and strain effects upon both wetting and dewetting. SFM reveals that the wetting water layer is one monolayer thick, slightly thinner than a single layer of graphene. Raman spectra exhibit a reduction of the graphene D' peak intensity upon wetting, and a recurrence of the peak when the water layer dewets the slit pore. We attribute the D' peak to direct contact of the graphene with the ionic mica surface in dry conditions. Analyses of the 2D and G peak positions, the corresponding peak positions and the widths, imply that graphene on dry mica is charge doped and variably strained. A monolayer of water in between graphene and mica removes doping and reduces strains. This supports that in dry conditions graphene is in direct contact with the mica surface, while a complete monolayer of water wetting the slit pore decouples the graphene from the mica substrate both mechanically and electronically.