Quantifying ion-induced defects and Raman relaxation length in graphene

Raman scattering is used to study disorder in graphene subjected to low energy (90 eV) Ar+ ion bombardment. The evolution of the intensity ratio between the G band (1585 cm−1) and the disorder-induced D band (1345 cm−1) with ion dose is determined, providing a spectroscopy-based method to quantify the density of defects in graphene. This evolution can be fitted by a phenomenological model, which is in conceptual agreement with a well-established amorphization trajectory for graphitic materials. Our results show that the broadly used Tuinstra-Koenig relation should be limited to the measure of crystallite sizes, and allows extraction of the Raman relaxation length for the disorder-induced Raman scattering process.