Published: November 11, 2011 r2011 American Chemical Society 5401 dx.doi.org/10.1021/nl2031037 | Nano Lett. 2011, 11, 5401–5407 LETTER pubs.acs.org/NanoLett Nitrogen-Doped Graphene: Efficient Growth, Structure, and Electronic Properties D. Usachov,* ,† O. Vilkov, † A. Gr€ uneis, ‡,§ D. Haberer, ‡ A. Fedorov, † V. K. Adamchuk, † A. B. Preobrajenski, || P. Dudin, ^ A. Barinov, ^ M. Oehzelt, z C. Laubschat, # and D. V. Vyalikh †,# † St. Petersburg State University, St. Petersburg, 198504, Russia ‡ IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany § Faculty of Physics, Vienna University, Strudlhofgasse 4, 1090 Wien, Austria ) MAX-lab, Lund University, Box 118, 22100 Lund, Sweden ^ Sincrotrone Trieste S.C.p.A., Area Science Park, I-34012 Basovizza, Trieste, Italy z Helmholtz-Zentrum Berlin f€ ur Materialien und Energie, BESSY II, Albert-Einstein-Strasse 15, D-12489 Berlin, Germany # Institute of Solid State Physics, Dresden University of Technology, D-01062 Dresden, Germany G raphene is one of the amazing recent developments in modern science and one of the most promising materials for implementation in the next generation electronic devices. Because of graphene’s unique properties, devices based on mechanisms alternative to classical charge transport come into reach that would allow unprecedented speed of the graphene- based transistors. However, being a zero-gap semiconductor, pure graphene does not seem to be ready for its direct imple- mentation. Presently, many research efforts are directed toward the elaboration of methods that allow inducing and fine-tuning of a band gap in graphene. 1À3 We have recently demonstrated that graphene hydrogenation, that is, treatment with atomic hydro- gen, gives rise to changes in the electronic properties and allows one to induce of a gap in graphene’s electronic structure due to rehybridization from sp 2 - to sp 3 -bonded carbon upon hydro- genation, which leads to gap values of up to ∼1.0 eV at 8% hydrogen coverage. 3,4 The promising approach for tuning and controlling the electronic properties of graphene is doping with heteroatoms, similar to that elaborated for the silicon-based technology. Thus, doping with boron or nitrogen atoms allows graphene transformation into p- or n-type semiconductor respectively, 5,6 accompanied by opening of a band gap. 7 The ability to tune the electronÀhole doping in graphene opens perspectives for developing tunable electronic devices through external control of the electronÀphonon coupling. 8 Another issue is that n- or p-doped graphene is also a promising candi- date for applications in electrochemical biosensing, 9 lithium batteries, 10 and fuel cells. 11 In the present work, we focus on the implementation of nitrogen for the n-type doping of graphene. A nitrogen atom contains one additional electron and when replacing a carbon atom in the graphene lattice, novel electronic properties can be envisaged. Generally, elaboration of recipes for incorporating nitrogen into a matrix of carbon-based materials in order to reach the desirable semiconducting properties is a rapidly developing area in the carbon technology. 12À18 This issue was rather intensively explored and discussed, for instance, in the scope of single-wall carbon nanotubes (CNTs), 19À23 which could be considered as rolled-up graphene layers. However, experimental information about the doping level and band structure of doped CNTs is still lacking. Here the study of N-graphene becomes essential, since experimentally measured band structure of N-graphene can be used to predict the band structure of N-doped CNTs by zonefolding method. 24 It is widely established that incorporation of nitrogen atoms into the matrix of sp 2 -bonded carbon can lead to appearance of Received: September 7, 2011 Revised: November 9, 2011 ABSTRACT: A novel strategy for efficient growth of nitrogen-doped graphene (N-graphene) on a large scale from s-triazine molecules is presented. The growth process has been unveiled in situ using time- dependent photoemission. It has been established that a postannealing of N-graphene after gold intercalation causes a conversion of the N environment from pyridinic to graphitic, allowing to obtain more than 80% of all embedded nitrogen in graphitic form, which is essential for the electron doping in graphene. A band gap, a doping level of 300 meV, and a charge-carrier concentration of ∼8 Â 10 12 electrons per cm 2 , induced by 0.4 atom % of graphitic nitrogen, have been detected by angle-resolved photoemission spectroscopy, which offers great promise for implementation of this system in next generation electronic devices. KEYWORDS: Graphene, nitrogen doping, electronic structure, synthesis, triazine, ARPES