Growth of coronene on (100)- and (111)-surfaces of fcc-crystals

Abstract

Abstract The growth of coronene thin films is studied via low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) comparing metal substrates with different lattice constants, different surface symmetry, and also with surface passivation, namely Cu(111), Ag(111), Ag(100), and (100)-terminated KCl/Ag(100). In particular, we investigate the evolution of the coronene lattice parameters upon coverage- and temperature-variation. On the pristine metal surfaces we observe disordered phases at low coverage. Further deposition leads to hexagonal arrangement of the molecules. With increasing coverage the lattice constant decreases continuously, whereas on Cu(111) the molecular unit cell additionally rotates w.r.t. the substrate lattice. We also discuss the interaction mechanisms that are responsible for this behavior. Due to the continuous change in the lattice dimensions we observe many incommensurate structures that were stable during our measurements, however the close-packed structures we found were always commensurate. The use of a passivation layer leads to the formation of a bulk-like structure consisting of molecules adsorbed in an upright standing manner which is stable at low temperatures only.