Lattice disordering in graphite under rare-gas ion irradiation studied by Raman spectroscopy

We present real-time Raman measurements on graphite under 3-keV rare-gas ion irradiation. The graphite lattice disorder is estimated by the relative intensity ratio of the disorder-induced peak ({~}1360 cm^-1) with respect to the Raman active E2g2 mode peak ({~}1580 cm^-1), and the peak intensity ratio is found to be proportional to the square root of ion irradiation time in the beginning of ion irradiation at doses below 2.5×{}10¹⁷ ions/m². At the higher doses the peak intensity ratio reaches saturation. The lattice disordering rate constant steeply increases for lower mass as ion mass increases, slowly reaching a saturation value for the higher mass. Ion-mass dependence of the disordering rate is well explained by the interdefect distance model calculation.