title: Entropic stabilization of large adsorbates on weakly binding substrates-a thermal desorption and scanning tunneling microscopy study.
abstract: Thermal desorption (TD) of oligopyridine from HOPG shifts from approximately 700 to approximately 500 K when going from (sub-)mono- to multilayers. Stabilization of low coverages results from a continuous shift of the frequency factor nu, from 10(15) s(-1) for submonolayers to 10(24) s(-1) for multilayers, whereas the desorption barrier is virtually constant. Applying transition state theory (TST), we can explain this by a change from rotationally/translationally mobile, flat-lying molecules (submonolayers) to immobile, upright molecules (multilayers). At room temperature, (time resolved) scanning tunneling microscopy (STM) gives evidence for the existence and the stability of the mobile phase.
authors.affiliation: Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Roos
authors.forename: Achim
authors.initials: A
authors.lastname: Breitruck
authors.forename: Harry E
authors.initials: HE
authors.lastname: Hoster
authors.forename: R Jürgen
authors.initials: RJ
authors.lastname: Behm