Who: Dmitry Yu. Usachov. St. Petersburg State University, Russia
Place: Donostia International Physics Center
Date: Wednesday, 26 July 2017, 12:00
The most outstanding properties of graphene stem from its Dirac spectrum of electronic states. This spectrum can be strongly influenced by a contact with other materials and a presence of defects or embedded impurities. This opens wide opportunities for tuning such properties as the width of a band gap, the type and concentration of charge carriers. This work is aimed at development of approaches for purposeful modifications of the graphene electronic structure and related properties.
Photoelectron spectroscopy with angular and spin resolution is a powerful method for the study of modifications in the electronic structure of graphene, induced by interaction with substrate, incorporation of impurities, adsorption and functionalization [1-3]. Here it is demonstrated how the combination of photoemission with scanning tunneling microscopy and spectroscopy, electron and photoelectron diffraction, X-ray absorption spectroscopy, Raman spectroscopy and DFT simulations allows deep insight into the structure and electronic properties of pure and impurity-doped graphene.
In particular, a promising approach for the graphene band gap engineering is to introduce a sublattice asymmetry by means of selective incorporation of impurities into only one of the two carbon sublattices. It is shown that boron impurities embedded in graphene on the Co(0001) surface preferably occupy one sublattice due to a site-specific interaction with the substrate. Calculations predict that such boron doped graphene possesses a band gap that can be precisely controlled by the dopant concentration. B-doped graphene with doping asymmetry is, thus, a novel material, which is worth considering as a good candidate for electronic applications.
 D. Usachov et al., Epitaxial B-Graphene: Large-Scale Growth and Atomic Structure. ACS Nano 9, 7314 (2015).
 D. Usachov et al., The Chemistry of Imperfections in N-Graphene. Nano Lett. 14, 4982 (2014).
 D. Usachov et al., Observation of Single-Spin Dirac Fermions at the Graphene/Ferromagnet Interface. Nano Lett. 15, 2396 (2015).