Dresden 2014 – scientific programme
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DS: Fachverband Dünne Schichten
DS 18: Organic Thin Films I
DS 18.11: Talk
Wednesday, April 2, 2014, 12:15–12:30, CHE 91
Diffraction Limited Polarized Raman Microscopy for Probing Nanoscale Structural Order — •Xiao Wang1, Katharina Broch2, Reinhard Scholz3, Frank Schreiber2, Alfred J. Meixner1, and Dai Zhang1 — 1Institute of Physical and Theoretical Chemistry, University of Tübingen, Auf der Morgenstelle 18, 72076 Tübingen — 2Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen — 3Institut für Angewandte Photophysik, Technische Universität Dresden, George-Bähr-Straße 1, 01069, Dresden
Radially or azimuthally polarized doughnut laser beams (RPDB or APDB) are combined with topography studies of pentacene thin films, allowing to correlate Raman spectroscopy with intermolecular interactions depending on the particular pentacene modification. Polarization dependent Raman spectra of the C-H bending vibrations are resolved layer by layer within a thin film of approximately 20 nm thickness. The variation of the Raman peak positions indicates changes in the molecular orientation and in the local environment at different heights of the pentacene film. This method reveals the local structural order and the polymorph at different locations within the same pentacene thin film, depending mainly on its thickness: The first few monolayers grow in a thin film phase, but for larger film thicknesses, the morphology evolves towards the crystal bulk phase with a larger tilting angle of the pentacene molecules against the substrate normal.