▎ 摘　　要

We present systematical Raman studies of nitrogen doped graphene (NG). Defective graphene by Ar+ ion bombardment was also studied for comparison. It was found that the defects/nitrogen dopants in NG are not homogenous. Our results also suggest that the G peak position and I-2D/I-G ratio cannot be simply used as fingerprint of doping concentration in NG. Both doping and compressive strain (as verified by transmission electron microscope) contribute to the shift of Raman peaks, while both doping and lattice defects contribute to the attenuation of 2D peak. Finally, the nature of defects in NG was probed and found that they are boundary defects. The detail analysis of the evolution of Raman spectra in NG would greatly help on the characterization and future application of this novel material. (C) 2013 Elsevier Ltd. All rights reserved.