Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Weiche Materie Poster: Do., 13:00–15:30 D-P328
Microspectroscopy of organic thin films
Rainer Fink 1 , Gregor Bozek 1 , Jörg Raabe 2 , David Kilcoyne 3
1 Univ. Erlangen, Physikalische Chemie II, Egerlandstr. 3, D-91058 Erlangen – 2 Paul
Scherrer Institut, SLS, WSLA/225, CH-5232 Villigen-PSI – 3 ALS, 1 Cyclotron Road,
MS 7R0222, LBNL,Berkeley, CA 94720 - 8225
Zone-plate base scanning-transmission microspectroscopy offers manyfold different application
with lateral resolutions well below 50 nm. The operation of the microscope in
either He atmosphere or in vacuum allows the investigation of thin solid films and liquid
films in wet cells. The BMBF funded PolLux project, which is presently under commissioning
at the Swiss Light Source (Paul Scherrer Institut, Villigen) will be an easy to use
microspectroscopy facility which offers a wide variety of experimental possibilities in
the photon energy range from 260 to 1100 eV. Within this project, we have performed
laterally resolved NEXAFS investigations of ultrathin organic films prepared either by
vacuum sublimation or by dip- or spin-coating from solution. Particular emphasis was
lying on structure-property relationships in thus prepared samples. The materials under
investigation were ranging from supramolecular ligand stabilised assemblies with
paramagnetic ions (which may also regarded as molecular magnets containing Fe and
Mn ions), heteroaromates, metal-organic charge-transfer complexes, binary liquid films
(see Fig. 1)and films from triblock copolymers. In all cases the NEXAFS contrast at
the respective absorption edges was used for contrast improvement of the images or - in
the case of multicomponent samples - to identify the different chemical species within
the film. Nano- and microcrystalline growth is observed in many samples thus allowing
to utilize the NEXAFS linear dichoism to monitor the molecular orientations. Due to
the high photon flux density in the focussed beam radiation damage has been checked
carefully. In contrast to other spectromicroscopies (e.g. XPEEM) illumination times in
the millisecond range reduces damage significantly as demonstrated for the extremely
sensity molecular magnets. This project is funded by the BMBF under contract 05
KS4WE1/6.
Fig. 1: STXM micrographs recorded at two different photon
energies of a binary liquid crystal film prepared on
100 nm thick Si3N4-membranes (image size: 25 µm 2 ) .
Contrast reversal is the signature for the two different
species.