Beyond defect formation: Spectroscopic characterization of plasma-induced structural and electronic transformations in graphene

Recent research suggests plasma-induced hydrogenation is an efficient method for inducing a band-gap in graphene. To date, the characterization of plasma treatment-induced chemical changes is performed almost exclusively by Raman spectroscopy with the extent of hydrogenation presented as the evolution defect structures in the sp² lattice of graphene. Alarmingly, almost no attention is given to the concurrent electronic modification. Here, x-ray induced Auger emission spectroscopy is utilized to better understand the effect of plasma treatment on the electronic properties of graphene beyond the formation of defects as determined by Raman spectroscopy. The results indicate the fine structure of the C_KLL emission offers a suitable complement to Raman spectroscopy in assessing the extent of chemical and electronic changes induced by H₂ plasma treatments. Significant changes to the D-value, defined as the distance between local maxima and minima in the C_KLL Auger emission, are observed after only 30 s of treatment (p < 0.001), while the I_D/I_G ratio remains statistically equivalent (p = 0.441). The results indicate significant differences in the electronic properties of plasma-treated graphene are observed concomitant to sp² defect structures normally attributed to hydrogenation.