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Controlled modification of mono- and bilayer graphene in O2, H2and CF4plasmas

Felten, A. and Eckmann, A and Pireaux, J.-J. and Krupke, R. and Casiraghi, C. (2013):
Controlled modification of mono- and bilayer graphene in O2, H2and CF4plasmas.
In: Nanotechnology, 24 (35), p. 355705. IOP Publishing, ISSN 0957-4484,
[Article]

Abstract

In this work, covalent modification of mono- and bilayer graphene is achieved using tetrafluoromethane (CF4), oxygen and hydrogen RF plasma. Controlled modification of graphene is usually difficult to achieve, in particular with oxygen plasma, which is rather aggressive and usually leads to etching of graphene. Here we use x-ray photoelectron spectroscopy and Raman spectroscopy to show that mild plasma conditions and fine tuning of the number of functional groups can be obtained in all plasmas by varying parameters such as exposure time and sample position inside the chamber. We found that even for the usual harsh oxygen treatment the defect density could be lowered, down to one defect for 3.5 × 104 carbon atoms. Furthermore, we show that CF4 plasma leads to functionalization without etching and that graphene becomes an insulator at saturation coverage. In addition, the reactivity of mono- and bilayer graphene was studied revealing faster modification of monolayer in oxygen and CF4 plasma, in agreement with previous works. In contrast, similar modification rates were observed for both mono- and bilayer during hydrogenation. We attribute this discrepancy to the presence of more energetic species in the hydrogen plasma such as positive ions that could play a role in the functionalization process.

Item Type: Article
Erschienen: 2013
Creators: Felten, A. and Eckmann, A and Pireaux, J.-J. and Krupke, R. and Casiraghi, C.
Title: Controlled modification of mono- and bilayer graphene in O2, H2and CF4plasmas
Language: English
Abstract:

In this work, covalent modification of mono- and bilayer graphene is achieved using tetrafluoromethane (CF4), oxygen and hydrogen RF plasma. Controlled modification of graphene is usually difficult to achieve, in particular with oxygen plasma, which is rather aggressive and usually leads to etching of graphene. Here we use x-ray photoelectron spectroscopy and Raman spectroscopy to show that mild plasma conditions and fine tuning of the number of functional groups can be obtained in all plasmas by varying parameters such as exposure time and sample position inside the chamber. We found that even for the usual harsh oxygen treatment the defect density could be lowered, down to one defect for 3.5 × 104 carbon atoms. Furthermore, we show that CF4 plasma leads to functionalization without etching and that graphene becomes an insulator at saturation coverage. In addition, the reactivity of mono- and bilayer graphene was studied revealing faster modification of monolayer in oxygen and CF4 plasma, in agreement with previous works. In contrast, similar modification rates were observed for both mono- and bilayer during hydrogenation. We attribute this discrepancy to the presence of more energetic species in the hydrogen plasma such as positive ions that could play a role in the functionalization process.

Journal or Publication Title: Nanotechnology
Journal volume: 24
Number: 35
Publisher: IOP Publishing
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Fachgebiet Molekulare Nanostrukturen
Date Deposited: 18 Oct 2013 07:31
Official URL: http://dx.doi.org/10.1088/0957-4484/24/35/355705
Identification Number: doi:10.1088/0957-4484/24/35/355705
Funders: AF and CC acknowledge the Alexander von Humboldt foundation for financial support. AF acknowledges the FRS-FNRS for financial support.
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