Effects of Incident Electron Energy on Electron-Irradiated Graphene*

We investigate the effects of incident electron energy on electron-irradiated exfoliated graphene. The graphene is irradiated using scanning electron microscopy (SEM). The effects are studied using Raman spectroscopy. A range of electron energies, 0.5 keV, 1 keV, 2 keV, 4 keV, 8 keV, 16 keV, 25 keV, and 30 keV, is utilized. We observe that the I_D/I_G ratio varies as a function of electron energy, following the established two-stage model of graphene, highlighting the energy dependence of defect formation. Additionally, the full-width-at-half-maximum (FWHM) of the D peak decreases from 23.19 cm⁻¹ at 298 K to 19.15 cm⁻¹ at 493 K, while the phonon lifetime increases from 0.457 ps to 0.554 ps. This behavior contrasts with materials like silicon and gallium arsenide (GaAs), where the FWHM of phonon peaks typically increases with temperature due to enhanced phonon-phonon scattering. The decreasing FWHM in graphene suggests defect annealing or structural reorganization occurs at elevated temperatures, leading to reduced phonon scattering. These findings offer valuable insights into the interplay between temperature, energy, and phonon transport in graphene.