• in-situ Raman spectroscopy;
  • graphene;
  • Joule heating;
  • doping

In-situ Raman spectroscopy was performed on chemical vapor deposited graphene microbridge (3 μm × 80 μm) under electrical current density up to 2.58 × 108 A/cm2 in ambient conditions. We found that both the G and the G′ peak of the Raman spectra do not restore back to the initial values at zero current, but to slightly higher values after switching off the current through the microbridge. The up-shift of the G peak and the G′ peak, after switching off the electrical current, is believed to be due to p-doping by oxygen adsorption, which is confirmed by scanning photoemission microscopy. Both C–O and C=O bond components in the C1s spectra from the microbridge were found to be significantly increased after high electrical current density was flown. The C=O bond is likely the main source of the p-doping according to our density functional theory calculation of the electronic structure. Copyright © 2014 John Wiley & Sons, Ltd.