Effect of fluorination on the molecular packing of perfluoropentacene and pentacene ultrathin films on Ag (111)

Abstract

The growth of perfluoropentacene (PFP) and pentacene (PEN) ultrathin films on Ag(111) has been investigated using low-temperature scanning tunneling microscopy. To understand the influence that perfluorination of the parent molecule has on its resultant packing structure, the results are compared against each other in the framework of morphological differences. Perfluorination leads to a different packing structure in the first monolayer. We observed only one closely packed arrangement with periodic dislocation lines for PFP molecules, while for PEN molecules, there are two coexisting arrangements in the first monolayer. Monolayers of each molecule are commensurate with the underlying substrate with long axes of both molecules aligned in the [11̄0] direction along the silver surface. The disparity in arrangements is attributed to the difference in peripheral atoms of the two molecules. Additional photoemission spectroscopy studies reveal that PFP physisorbs on Ag (111). © 2010 American Chemical Society.