Abstract
First-order Raman spectra of pyrolytic graphite (PG) and highly oriented pyrolytic graphite (HOPG) were recorded in situ up to 2670K and 2491K, respectively, using a development of wire-loop heating cell technique attached to a UV-Raman spectrometer (244nm). Raman shift of the E2g in-plane stretching mode of graphite (G band) is used to discuss the anharmonicity by a comparison with calculations in the density-functional theory (DFT). High temperature Raman shifts are well described by anharmonic DFT calculations [1] up to 900K. Anharmonicity is also determined from the temperature dependence of the Raman linewidth. The quartic term of phonon–phonon scattering process dominates at high temperature with respect to electron–phonon coupling that causes a slight decrease of linewidth with increasing temperature below 1000K. The G band position is determined with a good reproducibility to 2700K and can be used as a thermometer for in situ studies. Deep UV-Raman proves a viable solution for expanding significantly the temperature range for studying in situ vibrational properties of condensed matter, and particularly the monitoring of carbon-based material processing.
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