Atomic-scale characterization of nitrogen-doped graphite: Effects of   dopant nitrogen on the local electronic structure of the surrounding carbon   atoms
  We report the local atomic and electronic structure of a nitrogen-doped graphite surface by scanning tunnelling microscopy, scanning tunnelling spectroscopy, X-ray photoelectron spectroscopy, and first-principles calculations. The nitrogen-doped graphite was prepared by nitrogen ion bombardment followed by thermal annealing. Two types of nitrogen species were identified at the atomic level: pyridinic-N (N bonded to two C nearest neighbours) and graphitic-N (N bonded to three C nearest neighbours). Distinct electronic states of localized {\pi} states were found to appear in the occupied and unoccupied regions near the Fermi level at the carbon atoms around pyridinic-N and graphitic-N species, respectively. The origin of these states is discussed based on the experimental results and theoretical simulations. 
Takahiro Kondo, Simone Casolo, Tetsuya Suzuki, Taishi Shikano,   Masataka Sakurai, Yoshihisa Harada, Makoto Saito, Masaharu ...
cond-mat.mtrl-sci