Effect of oxygen plasma etching on graphene studied using Raman spectroscopy and electronic transport measurements

In this paper, we report a study of graphene and graphene field effect devices after their exposure to a series of short pulses of oxygen plasma. Our data from Raman spectroscopy, back-gated field-effect and magnetotransport measurements are presented. The intensity ratio between Raman 'D' and 'G' peaks, I_D/I_G (commonly used to characterize disorder in graphene), is observed to initially increase almost linearly with the number (N_e) of plasma-etching pulses, but later decreases at higher N_e values. We also discuss the implications of our data for extracting graphene crystalline domain sizes from I_D/I_G. At the highest N_e value measured, the '2D' peak is found to be nearly suppressed while the 'D' peak is still prominent. Electronic transport measurements in plasma-etched graphene show an up-shifting of the Dirac point, indicating hole doping. We also characterize mobility, quantum Hall states, weak localization and various scattering lengths in a moderately etched sample. Our findings are valuable for understanding the effects of plasma etching on graphene and the physics of disordered graphene through artificially generated defects.