Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 28: Adsorption an Oberfl
ächen III

O 28.5: Vortrag

Donnerstag, 27. März 2003, 12:15–12:30, FOE/ANOR

Determination of the cohesive energy of graphite from thermal desorption spectroscopy of polyaromatic hydrocarbons adsorbed on HOPG — •Renju Zacharia, Hendrik Ulbricht, and Tobias Hertel — Abteilung für Physikalische Chemie, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin.

The interaction between graphene sheets, i.e. the cohesive energy of graphite, is dominated by dispersion forces. Graphite is therefore frequently regarded as the prototype of a van der Waals bonded system. However, the experimental and theoretical determination of the strength of this interaction remains a true challenge. Here, we present a thermal desorption study on the interaction of four different polyaromatic hydrocarbons (PAH’s) (benzene, naphthalene, coronene, ovalene) with highly oriented pyrolytic graphite (HOPG). The observed activation energies for desorption are used to discriminate contributions to the binding energy arising from carbon atoms with two and three neighbouring carbons. The contribution of the latter may be used to extrapolate the observed molecular binding energies with graphite to those expected for larger PAH’s which - in the limit of an infinitely extended adsorbate molecule - would yield the interaction strength between graphene sheets.