Ion-irradiation effects on the phonon correlation length of graphite studied by Raman spectroscopy

Real-time Raman measurements have been performed on graphite under 3-keV ${\mathrm{Ar}}^{+}$-ion irradiation with a time resolution of 6 sec. Ion flux of 3×${10}^{11}$ and 4×${10}^{10}$ ions/${\mathrm{cm}}^2$ sec are used. The graphite lattice damage is estimated by the relative intensity ratio of the disorder-induced peak (∼1360 ${\mathrm{cm}}^{\mathrm{-}1}$) with respect to the Raman-active ${\mathit{E}}_{2\mathit{g}}$-mode peak (∼1580 ${\mathrm{cm}}^{\mathrm{-}1}$). The relative intensity change in the Raman spectrum caused by the irradiation is explained in terms of a reduction in the phonon correlation length due to defects.