Highly ordered growth of PTCDA on epitaxial bilayer graphene

For using the unique electronic properties of graphene in future nanoelectronic devices, control of the band structure is essential. While it has been shown already in the literature that this can be achieved by the deposition of organic molecules, little attention has been paid so far to the precise structural characterization of the interface. Here, we report on the epitaxial growth of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) layers on graphene, epitaxially grown on silicon carbide (SiC). The description of low energy electron diffraction (LEED) patterns of graphene on SiC by multiscattering is revisited. By means of a home-made algorithm used to correct radial distortions of the LEED images we are able to provide precise structural data of the PTCDA layers. By that, two different point-on-line types of PTCDA could be identified, one of which has neither been reported on graphite nor on graphene before.