Requirement on Aromatic Precursor for Graphene Formation

We studied graphene growth from solid, aromatic precursors at low temperature (similar to 400 degrees C) on a metal surface via high vacuum (6 x 10(-6) mbar) chemical vapor deposition. A set of conjugated and condensed aromatic precursor molecules, i.e., structural isomers of terphenyl and anthracene are compared. While p-terphenyl and m-terphenyl were found to be excellent precursors for the formation of graphene, no graphene was obtained from o-terphenyl or anthracene. We propose a reaction mechanism that explains the differing growth products. The key requirement for the synthesis of graphene is a three-dimensional nature and suitable molecular structure of the precursor. Its incorporation into a flat aromatic system on a metal surface has to provide sufficient energy gain for the polymerization to occur.