Raman-scattering and transmission-electron-microscopy studies of fluorine-intercalated graphite fibers CxF (7.8≥x≥2.9)

A. M. Rao, A. W. P. Fung, S. L. di Vittorio, M. S. Dresselhaus, G. Dresselhaus, M. Endo, K. Oshida, and T. Nakajima
Phys. Rev. B 45, 6883 – Published 15 March 1992
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Abstract

Raman-scattering and transmission-electron-microscopy (TEM) experiments are reported which provide information on the microstructure of fluorine-intercalated graphite fibers (CxF) for stoichiometries in the range 7.8≥x≥2.9. Lorentzian fits to our Raman spectra indicate the presence of a doublet near 1600 cm1 and a broad line near 1360 cm1. An anomalous frequency downshift of the doublet was observed in CxF fibers upon increase in the intercalate concentration, unlike the behavior observed in other acceptor graphite intercalation compounds. This downshift in frequency of the doublet can be understood in terms of a decrease in the hole concentration in the graphene layers with increasing fluorine concentration, resulting in an increase in the in-plane lattice constant and a decrease in the in-plane mode frequency. These Raman results are consistent with high-resolution TEM experiments on the same fibers. Lattice fringe images of CxF fibers show wavy fringes, and the waviness is identified with semi-ionic (covalent) bonding. Evidence for unintercalated graphite regions is also presented. As the fluorine concentration of the CxF fibers increases to high values, the amount of waviness increases.

  • Received 15 July 1991

DOI:https://doi.org/10.1103/PhysRevB.45.6883

©1992 American Physical Society

Authors & Affiliations

A. M. Rao

  • Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

A. W. P. Fung

  • Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

S. L. di Vittorio

  • Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

M. S. Dresselhaus

  • Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
  • Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

G. Dresselhaus

  • Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

M. Endo and K. Oshida

  • Department of Electrical Engineering, Faculty of Engineering, Shinshu University, Nagano 380, Japan

T. Nakajima

  • Division of Molecular Engineering, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606, Japan

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Vol. 45, Iss. 12 — 15 March 1992

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