Molecular and electronic structure of PTCDA on bilayer graphene on SiC(0001) studied with scanning tunneling microscopy

Epitaxial growth of graphene on SiC surfaces by solid state graphitization is a promising route for future development of graphene based electronics. In the present work we study the morphology and molecular scale structure of monolayer films of 3,4,9,10‐perylene tetracarboxylic dianhydrid (PTCDA) on bilayer graphene on SiC(0001) by scanning tunneling microscopy (STM). First we discuss how the PTCDA molecules adsorb on bilayer graphene. We specially regard the density of PTCDA molecules at monolayer coverage. From the comparison with experiments on HOPG (Au(111) and Ag(110) from literature) we infer a non‐planar adsorption geometry of PTCDA molecules on bilayer graphene. The electronic structure of the surrounding bilayer graphene substrate is investigated via scanning tunneling spectroscopy (STS) and reveals n‐type doping of bilayer graphene during adsorption of PTCDA. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)