ANNEALING EXPERIMENT OF ION-IRRADIATED GRAPHITE BY LASER RAMAN-SPECTROSCOPY

The annealing behavior of highly oriented pyrolytic graphite foils irradiated at room temperature was systematically investigated in terms of irradiation dose by means of Raman spectroscopy. A remarkable decrease in the intensity ratio of the defects peak at 1355 cm-1 to the Raman-allowed graphite peak at 1580 cm-1, I1355/I1580, could be seen on annealing at temperatures as low as < 300-degrees-C only for the foils before irradiation-induced amorphization. On annealing, two linear relationships were appreciable between the peak width of 1580 cm - 1 and I1355/I1580. One was considered to correspond to the accumulation of defects in the basal plane, which are unstable and easily annealed at low annealing temperatures, while the other to that of the disordered structure between the basal planes, which is stable and induces amorphization. The two linear relations were very similar to those observed in the irradiated graphites but the change was opposite in direction.