Raman studies of benzene-derived graphite fibers

Carbon fibers prepared from thermal decomposition of benzene at {~} 1100^∘{}C are studied by Raman spectroscopy as a function of heat-treatment temperature. The structural ordering at each heat-treatment temperature is monitored by observation of both the Raman-allowed E_2g₂ mode at 1580 cm^-1 and the disorder-induced lines at {~} 1360 cm^-1 in the first-order spectra and at 2730 and 2970 cm^-1 in the second-order spectra. Raman and resistivity results indicate three characteristic heat-treatment temperatures relevant to the establishment of in-plane and interplanar ordering. Using fibers heat treated to the maximum available temperature of 2900^∘{}C, Raman spectroscopy shows that single-staged fibers can be prepared by acceptor intercalation, in agreement with direct Debye-Scherrer x-ray measurements. Resistivity measurements on pristine fibers previously heat treated to 2900^∘{}C show a metallic temperature dependence with ρ=70 {μ}{Ω} cm at 300 K and a residual resistance ratio of 1.5. Upon intercalation, a resistivity ρ=7 {μ}{Ω} cm at 300 K and a residual resistance ratio of 5 is achieved. Raman-spectroscopy and temperature-dependent resistivity measurements demonstrate that the benzene-derived fibers exhibit the highest degree of ordering achieved in fibers and provide an attractive host material for intercalation.