A Raman investigation into the effect of temperature on ion-induced damage of graphite

Samples of highly-orientated pyrolytic graphite (HOPG) have been irradiated with 5 keV He+ and Xe+ ions at temperatures of 298 K and 100 K. Irradiation-induced damage has been monitored using Raman spectroscopy through analysis of the intensity of the D-band with respect to the G band (ID/IG ratio). A significant increase in the rate of damage accumulation was observed after ion-irradiation at 100 K, leading to a very broad Raman spectrum. The emergence of a broad feature at ∼1500 cm−1 is also observed and attributed to a significant breakdown of lattice order and the presence of a more amorphous system. This feature is thought to be due to a carbon-ion interaction.