Localized state and charge transfer in nitrogen-doped graphene

Frederic Joucken, Yann Tison, Jerome Lagoute, Jacques Dumont, Damien Cabosart, Bing Zheng, Vincent Repain, Cyril Chacon, Yann Girard, Andres Rafael Botello-Mendez, Sylvie Rousset, Robert Sporken, Jean-Christophe Charlier, Luc Henrard

Published 2012-04-16Version 1

Nitrogen-doped epitaxial graphene grown on SiC(000?1) was prepared by exposing the surface to an atomic nitrogen flux. Using Scanning Tunneling Microscopy (STM) and Spectroscopy (STS), supported by Density Functional Theory (DFT) calculations, the simple substitution of carbon by nitrogen atoms has been identifi?ed as the most common doping con?guration. High-resolution images reveal a reduction of local charge density on top of the nitrogen atoms, indicating a charge transfer to the neighboring carbon atoms. For the fi?rst time, local STS spectra clearly evidenced the energy levels associated with the chemical doping by nitrogen, localized in the conduction band. Various other nitrogen-related defects have been observed. The bias dependence of their topographic signatures demonstrates the presence of structural con?gurations more complex than substitution as well as hole-doping.