Aqueous-phase oxidation of epitaxial graphene on the silicon face of SiC(0001)

Md Zakir Hossain, Maisarah B A Razak, Shinya Yoshimoto, Kozo Mukai, Takanori Koitaya, Jun Yoshinobu, Hayato Sone, Sumio Hosaka, Mark C Hersam

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Abstract

To explore the chemical and electronic states of oxidized epitaxial graphene (EG) grown on the Si face of SiC(0001), we employ the Hummers oxidizing agents (H2SO4 + NaNO3 + KMnO4) under different reaction conditions that oxidize the graphene layer. The resulting material is characterized with scanning tunneling microscopy (STM), scanning tunneling spectroscopy (STS), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). A mild "drop-cast" procedure at 60 C is found to be equally effective at oxidizing EG as the conventional Hummers procedure. This aqueous-phase oxidation reaction appears to proceed in an autocatalytic manner as indicated by the concurrent observation of patches of oxidized and clean graphene areas in atomically resolved STM images on partially oxidized EG. STS further reveals substantial changes in electronic structure for oxidized EG including the opening of a local band gap of ∼0.4 eV. The oxidation is confined to the graphene layers as verified by XPS characterization of the underlying SiC substrate. In contrast to EG oxidized in ultrahigh vacuum that contains only epoxy groups and can be fully reverted back to pristine EG following annealing at 260 C, aqueous-phase oxidized EG possesses carbonyl and hydroxyl groups in addition to the dominant epoxy groups and thus remains partially oxidized even following annealing at 1000 C.

Original languageEnglish
Pages (from-to)1014-1020
Number of pages7
JournalJournal of Physical Chemistry C
Volume118
Issue number2
DOIs
Publication statusPublished - Jan 16 2014

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Energy(all)

Cite this

Hossain, M. Z., Razak, M. B. A., Yoshimoto, S., Mukai, K., Koitaya, T., Yoshinobu, J., ... Hersam, M. C. (2014). Aqueous-phase oxidation of epitaxial graphene on the silicon face of SiC(0001). Journal of Physical Chemistry C, 118(2), 1014-1020. https://doi.org/10.1021/jp4092738