Visualizing Individual Nitrogen Dopants in Monolayer Graphene
  In monolayer graphene, substitutional doping during growth can be used to alter its electronic properties. We used scanning tunneling microscopy (STM), Raman spectroscopy, x-ray spectroscopy, and first principles calculations to characterize individual nitrogen dopants in monolayer graphene grown on a copper substrate. Individual nitrogen atoms were incorporated as graphitic dopants, and a fraction of the extra electron on each nitrogen atom was delocalized into the graphene lattice. The electronic structure of nitrogen-doped graphene was strongly modified only within a few lattice spacings of the site of the nitrogen dopant. These findings show that chemical doping is a promising route to achieving high-quality graphene films with a large carrier concentration. 
Liuyan Zhao, Rui He, Kwang Taeg Rim, Theanne Schiros, Keun Soo Kim,   Hui Zhou, Christopher Guti\'errez, S. P. Chockalingam,...
cond-mat.mtrl-sci