Determination of PMMA Residues on a Chemical-Vapor-Deposited Monolayer of Graphene by Neutron Reflection and Atomic Force Microscopy

Ruiheng Li, Zongyi Li, Elias Pambou, Philipp Gutfreund, Thomas Waigh, John R.P. Webster, Jian Lu

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    Abstract

    Chemical vapor deposition (CVD) is now a well-established method for creating monolayer graphene films. In this method, poly(methyl methacrylate) (PMMA) films are often coated onto monolayer graphene films to make them mechanically robust enough for transfer and further handling. However, it is found that PMMA is hard to remove entirely, and any residual polymers remaining can affect graphene's properties. We demonstrate here a method to determine the amount of PMMA remaining on the graphene sheet fabricated from CVD by a combined study of Raman scattering, atomic force microscopy, and neutron reflection. Neutron reflectivity is a powerful technique which is particularly sensitive to any interfacial structure, so it is able to investigate the density profile of the residual PMMA in the direction perpendicular to the graphene film surface. After the standard process of PMMA removal by acetone-IPA cleaning, we found that the remaining PMMA film could be represented as a two-layer model: an inner layer with a thickness of 17 Å and a roughness of 1 Å mixed with graphene and an outer diffuse layer with an average thickness of 31 Å and a roughness of 4 Å well mixed with water. On the basis of this model analysis, it was demonstrated that the remaining PMMA still occupied a significant fraction of the graphene film surface.

    Original languageEnglish
    Pages (from-to)1827-1833
    Number of pages7
    JournalLangmuir
    Volume34
    Issue number5
    Early online date5 Jan 2018
    DOIs
    Publication statusPublished - 6 Feb 2018

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