Experimental study of nitrogen-doped graphene by spectroscopic and probe methods of surface analysis

This work demonstrates an integrated approach for studying graphene films with various doping levels of nitrogen. The graphene films grown by a chemical vapor deposition technique were doped by treatment in ammonia radio-frequency plasma discharge. The graphene samples were investigated by x-ray photoelectron spectroscopy with a parallel registration of photoemission angular dependence. The depth-dependent changes in the valence band structure and the nitrogen peak position were recorded. The shift of valence band maximum relative to the initial value ( 0.13±0.04  eV ) was observed using ultraviolet photoelectron spectroscopy. The dispersion and the shift of π -plasmon maximum were registered while the percentage of nitrogen atoms in two-dimensional graphene network increased.