Their findings were surprising. "Some of the nitrogen atoms diffused from the graphene into the silicon carbide," explains Bocquet. "It was previously believed that the nitrogen bombardment only affected the graphene, but not the substrate material."
Although both samples were treated in the same way, they exhibited different nitrogen concentrations, but almost identical electronic doping: not all nitrogen atoms were integrated in the graphene lattice, nevertheless the number of electrons in the graphene rose as if this were the case. The key to this unexpected result lies in the different behaviour of the interface layers between graphene and substrate. For the epitaxial graphene, nothing changed: the interface layer remained stable, the structure unchanged. In the quasi-free-standing graphene, however, some of the hydrogen atoms between graphene and substrate were replaced with nitrogen atoms. According to Bocquet: "If you examine the quasi-free-standing graphene, you will find a nitrogen atom underneath the graphene coat in some places. These nitrogen atoms, although they are not part of the graphene, can dope the lattice without destroying it. This unforeseen result is very promising for future applications in micro- and nanoelectronics."Literature
J. Sforzini, P. Hapala, M. Franke, G. van Straaten, A. Stöhr, S. Link, S. Soubatch, P. Jelínek, T.-L. Lee, U. Starke, M. Švec, F. C. Bocquet, and F. S. Tautz, Structural and Electronic Properties of Nitrogen-Doped Graphene
, Phys. Rev. Lett. 116, 126805 – Published 24 March 2016Source