Our
research
interest is focussed on large pi-conjgated molecules which can form
thin
semiconducting films. Such films have been investigated over the last
years in
the context of optoelectronic devices, for instance, organic light
emitting
diodes (OLEDs) or organic field effect transistors (OFETs). We
fabricate these
films by sublimation of the organic molecules onto surfaces of single
crystals
under vacuum. The sublimation technique allows us to prepare films with
very
well defined thicknesses which can range from the submonolayer range up
to thicknesses
of several hundred nanometers.
The
role of the
substrate surface turns out to be very important. This surface is
usually that
of an inorganic single crystal, for example an Ag(111) or Au(111)
surface. Its properties (geometry and
chemical
composition) are decisive for the chemical bonding of the deposited
molecules,
and consequently their spectroscopic and structural properties at the
interface.
Hence our investigations usually start with surface sensitive
experiments which
give information on the adsorption and bonding of the large molecules
to the
substrate surface. Starting from the monolayer, we are then interested
in the
growth of multilayer films and their resulting optical and charge
transport
properties. Based on these results we try to develop new concepts for
the
optimization of devices based on organic semiconductor layers, e.g.
OFETs.