The adsorption and dynamics of organic molecules on surfaces is central
to fields as diverse as heterogenous catalysis, biomaterials interfaces,
molecular electronics or surface functionalisation e.g for sensor applications.
Scanning Tunneling Microscopy allows a direct, real-space view of atomic-scale
phenomena on surfaces to be obtained. In the talk, I will present recent
STM results concerning fundamental aspects of the adsorption of organic
molecules on metal surfaces.
In the first part, I will focus on the adsorption of the amino acid
cysteine on the Au(110) surface [1]. Cysteine is a chiral molecule, and
the cysteine/gold system has turned out to be a fascinating model system
for studying intermolecular recognition with chiral specificity. Also results
concerning molecular self-assembly of monodispersed nanometer sized clusters
of cysteine molecules will be touched upon.
Secondly, I will address the issue of surface diffusion. The motion
of atomic and molecular adsorbates across surfaces can be followed directly
by time resolved 'STM-movies'[2]. In the simplest picture of surface diffusion,
the adsorbate jumps between nearest neighbour sites. Recent results from
our group suggest this is not necessarily true for larger organic molecules.
In a comprehensive study of the diffusion of two largish, aromatic molecules,
DC and HtBDC, on Cu(110), we find the diffusion of these molecules to be
dominated by so-called long jumps, spanning multiple lattice sites [3].
Furthermore, the results demonstrate how molecules can be designed to alter
their diffusion properties.
[1]: A. Kuehnle, T.R. Linderoth, B. Hammer and F. Besenbacher, Nature
415, 891 (2002).
[2]: T. R. Linderoth et. al, Phys. Rev. Lett. 78, 4978 (1997).
[3]: M. Schunack, T.R. Linderoth et al, Phys. Rev. Lett. 88 156102-1
(2002).