Graphene and Hexagonal Boron Nitride Layers: Nanostructures with 3 bond hierarchy levels

Abstract

Single layers of carbon (graphene) and hexagonal boron nitride may be grown on transition metal surfaces. The substrates take the role of the support and allow due to their catalytic activity the growth of perfect layers by chemical vapor deposition. The layers are sp2 hybridized honeycomb networks with strong in plane σ- and weaker out of plane π-bonds to the substrate and to the adsorbates. This hierarchy in bond strength causes anisotropic elastic properties, where the sp2 layers are stiff in plane and soft out of plane. A corrugation of these layers imposes a third hierarchy level in bond energies (α-bonds), with lateral bonding of molecular objects with sizes between 1 and 5 nanometer. The lateral extra bond energies due to the polarizability α of the adsorbates are in the range of thermal energies kTR at room temperature and are particularly interesting for nanotechnology. The concomitant template function will be discussed. The peculiar bond hierarchy also imposes intercalation as another property of sp2 layer systems. Last but not least sp2 layer systems are particularly robust, i.e. survive immersion into liquids, which is a promise for sp2 layers being useful outside ultra high vacuum. [DOI: 10.1380/ejssnt.2010.62]