Veranstaltungsdetails

7.6.2011, 17:00
Jungiusstr. 11, Hörsaal AP

SFB 668 - Kolloquium

Dr. U. Starke (MPI Stuttgart):

Structural and electronic properties of epitaxial graphene on SiC(0001): Growth, transfer doping and atomic intercalation

Epitaxial graphene on SiC(0001) promises a scalable graphene technology. Different methods for homogeneous graphene growth and experimental techniques for layer counting will be reviewed. The graphene layers are n-doped due to the influence of a covalently bonded carbon interface layer. This doping level can be precisely tailored and completely neutralized by functionalizing the graphene surfaces with electronegative molecules. In particular the Fermi level can be shifted into the band gap of bilayer graphene. The influence of the interface can be completely eliminated by hydrogen intercalation. Hydrogen migrates under the interface layer, passivates the underlying SiC layer and decouples the graphene from the substrate. The interface layer alone transforms into a quasi-free standing monolayer and epitaxial monolayer graphene turns into a decoupled bilayer. By intercalation of Germanium the graphene layers can also be decoupled. In this process both p- and n-doping can be obtained, depending on the amount of Ge material intercalated. Both phases can be prepared in coexistence on the surface. In this way, lateral p-n junctions can be obtained on a sub-micron scale.