title: Structural evolution of perfluoro-pentacene films on Ag(111): transition from 2D to 3D growth.
abstract: The structural evolution and thermal stability of perfluoro-pentacene (PF-PEN) thin films on Ag(111) have been studied by means of low-temperature scanning tunnelling microscopy (STM), low-energy electron diffraction (LEED), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and thermal desorption spectroscopy (TDS). Well-defined monolayer films can be prepared by utilizing the different adsorption energy of mono- and multilayer films and selectively desorbing multilayers upon careful heating at 380 K, whereas at temperatures above 400 K, a dissociation occurs. In the first monolayer, the molecules adopt a planar adsorption geometry and form a well-ordered commensurate (6 × 3) superstructure where molecules are uniformly oriented with their long axis along the <110> azimuth. This molecular orientation is also maintained in the second layer, where molecules exhibit a staggered packing motif, whereas further deposition leads to the formation of isolated, tall islands. Moreover, on smooth silver surfaces with extended terraces, growth of PF-PEN onto beforehand prepared long-range ordered monolayer films at elevated temperature leads to needle-like islands that are uniformly aligned at substrate steps along <110> azimuth directions.
authors.affiliation: Molekulare Festkörperphysik, Philipps-Universität Marburg, D-35032 Marburg, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Götzen
authors.forename: Christian H
authors.initials: CH
authors.lastname: Schwalb
authors.forename: Christian
authors.initials: C
authors.lastname: Schmidt
authors.forename: Gerson
authors.initials: G
authors.lastname: Mette
authors.forename: Manuel
authors.initials: M
authors.lastname: Marks
authors.forename: Ulrich
authors.initials: U
authors.lastname: Höfer
authors.forename: Gregor
authors.initials: G
authors.lastname: Witte