Micro x-ray photoemission and Raman spectroscopic studies on bandgap tuning of graphene oxide achieved by solid state ionics device

Abstract

Micro x-ray photoemission spectroscopy (XPS) and Raman spectroscopy were performed to clarify the bandgap tuning mechanism of graphene oxide (GO) in an all-solid-state electric double layer transistor. A comparison of XPS spectra revealed that bandgap tuning occurs mainly via electrochemical reduction of phenol, carbonyl, and epoxy groups bonded to the basal plane of GO sheets. The corresponding valence band maximum offset was estimated to be 0.7 eV. Variation in the D and G bands in the Raman spectra indicated extensive generation of small and numerous sp2 domains upon electrochemical reduction. The C–C interatomic distances and C–C angles in the GO sheets were restored by reconstructing the sp2 network.