Regensburg 2004 – scientific programme

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O: Oberflächenphysik

O 14: Postersitzung (Adsorption an Oberflächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Phasenübergänge, Rastersondentechniken, Struktur und Dynamik reiner Oberflächen)

O 14.55: Poster

Monday, March 8, 2004, 18:00–21:00, Bereich C

UV-photoinduced modification and surface anisotropy of polyimide studied by X-ray absorption spectroscopy and spectromicroscopy — •Michael Zharnikov¹, Yukio Ouchi², Masaki Hasegawa³, and Andreas Scholl⁴ — ¹Angewandte Physikalische Chemie, Universität Heidelberg, 69120 Heidelberg, Germany — ²Department of Chemistry, Nagoya University, Nagoya, 464-8602 Japan — ³IBM Research, Tokyo Research Laboratory, Yamato, Kanagawa 242-8502, Japan — ⁴Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, CA 94720 USA

An alignment of liquid crystal (LC) molecules in a flat panel display is mediated by the anisotropic polyimide (PI) substrate. Whereas a conventional way to fabricate such a substrate is a mechanical rubbing of a PI, an alternative approach utilizes the irradiation of PI by linearly polarized UV-light. To get a basic understanding of the phenomenon of UV-light-induced anisotropy, we have performed NEXAFS spectromicroscopy measurements at the C, N, and O K-edges on a series of the polyimide films treated by linearly polarized UV-light through a mask. Fabricated patterns could be easily distinguished and imaged both for the parallel and perpendicular orientation of the electric field vectors of the UV- and synchrotron light. The UV-induced intensity changes of the characteristic absorption resonances at all probed absorption edges were monitored and related to the chemical modification of PI. From the analysis of the NEXAFS microspectra, the extent of the UV-induced anisotropy could be estimated in good agreement with our previous spectroscopic results.