Quantifying DefectsinGrapheneviaRamanSpectroscopy atDifferent Excitation Energies

We present a Raman study of Ar + -bombarded graphene samples with increasing ion doses. This allows us to have a controlled, increasing, amount of defects. We find that theratiobetweentheDandGpeakintensities,foragivendefect density, strongly depends on the laser excitation energy. We quantify this effect and present a simple equation for the determination of the point defect density in graphene via Raman spectroscopy for any visible excitation energy. We note that, for all excitations, the D to G intensity ratio reaches a maximumforaninterdefectdistance ∼3nm.Thus,agivenratio couldcorrespondtotwodifferentdefectdensities,aboveorbelowthemaximum.TheanalysisoftheGpeakwidthanditsdispersion with excitation energy solves this ambiguity.