Low-energy electron microscopy of graphene outside UHV: electron-induced removal of PMMA residues used for graphene transfer

•New technique to achieve a polymer-free CVD graphene is presented.•Slow electrons were used for the samples cleaning.•Graphene layers were counted by slow electrons in SEM/STEM (outside UHV). Two-dimensional materials, such as graphene, are usually prepared by chemical vapor deposition (CVD) on sel...

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Bibliographic Details
Published in:Journal of electron spectroscopy and related phenomena 2020-05, Vol.241, p.146873, Article 146873
Main Authors: Materna Mikmeková, E., Müllerová, I., Frank, L., Paták, A., Polčák, J., Sluyterman, S., Lejeune, M., Konvalina, I.
Format: Article
Language:English
Subjects:
Condensed Matter
Graphene
Physics
PMMA
Raman spectroscopy
Slow electron treatment
XPS
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Summary:•New technique to achieve a polymer-free CVD graphene is presented.•Slow electrons were used for the samples cleaning.•Graphene layers were counted by slow electrons in SEM/STEM (outside UHV). Two-dimensional materials, such as graphene, are usually prepared by chemical vapor deposition (CVD) on selected substrates, and their transfer is completed with a supporting layer, mostly polymethyl methacrylate (PMMA). Indeed, the PMMA has to be removed precisely to obtain the predicted superior properties of graphene after the transfer process. We demonstrate a new and effective technique to achieve a polymer-free CVD graphene — by utilizing low-energy electron irradiation in a scanning low-energy electron microscope (SLEEM). The influence of electron-landing energy on cleaning efficiency and graphene quality was observed by SLEEM, Raman spectroscopy (the presence of disorder D peak) and XPS (the deconvolution of the C 1s peak). After removing the absorbed molecules and polymer residues from the graphene surface with slow electrons, the individual graphene layers can also be distinguished outside ultra-high vacuum conditions in both the reflected and transmitted modes of a scanning low-energy (transmission) electron microscope.
ISSN:0368-2048
1873-2526
DOI:10.1016/j.elspec.2019.06.005