Raman Spectroscopy Study of Low Energy He~+ Ion Irradiation Effect in Graphene Transferred onto SiO_2*

摘要

We studied the low energy (5.4 keV) He~+ ion irradiation effect on the properties of chemical vapor deposited graphene transferred onto SiO_2/Si substrate. For a small dose density of 4 × 10~(12) He~+/cm~2, both the G and 2D bands in the Raman spectra exhibit blue-shift and the intensity ratio of the 2D and G peaks decreases. The intensity ratio of the D and G peaks increases a lot as the dose density is larger than 1.2 × 10~(13) He~+/cm~2. It suggests that before the formation of large amount of defects, low energy He~+ ion irradiation may induce charge-transfer doping in graphene due to the presence of polymer residues. Broad spatial distributions of the band shift and the intensity ratio indicate inhomogeneity of doping level in graphene.