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 ( similar to 1360 cm(-1)) with respect to the Raman active E(2g2) mode peak (similar to 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 2.5X10(17) ions/m(2). 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.