Raman microprobe observation of intercalate contraction in graphite intercalation compounds

Raman microprobe spectra of ${\mathrm{SbCl}}_5$, ${\mathrm{Br}}_2$, and ${\mathrm{FeCl}}_3$ graphite intercalation compounds have been obtained with a spatial resolution of 2 μm. Depletion of the intercalate was observed within 10 μm of the sample edge in the ${\mathrm{SbCl}}_5$-graphite samples, and this observation is found to be consistent with a model in which the intercalate contracts thermally as the sample is cooled after the intercalation reaction is completed. No depletion was observed in the ${\mathrm{Br}}_2$ and ${\mathrm{FeCl}}_3$ graphite intercalation compounds, consistent with the low intercalation temperature of the former and the small thermal expansion coefficient of the latter.