Conformation transition of single-layer graphene and its Raman spectroscopy

In this work, we report conformation transitions of pristine exfoliated graphenes after they are coated with a layer of polymethyl methacrylate and baked at 180 °C. Optical microscopes, scanning electron microscope are used to characterize the morphology changes. In the meantime, the characteristics of their Raman spectra are also studied before and after the conformation transition. After the transition, D-phonon mode in the Raman spectroscopy appears; G- and 2D-phonon modes show blue shift as well as broadening. It is suggested that the scrolling and curvature of graphene are responsible for these Raman characteristics. These results indicate the modification of the intrinsic properties of single-layer graphene during the standard device fabrication processes.