Dresden 2014 – scientific programme

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DS: Fachverband Dünne Schichten

DS 29: Organic Electronics and Photovoltaics V (joint session with CPP, HL, O)

DS 29.12: Talk

Wednesday, April 2, 2014, 18:00–18:15, ZEU 260

Reversible switching and light-induced structural changes in spin-coated thin films of Azobenzene-polymers — •Christopher Weber¹, Tobias Liebig¹, David Bléger², Stefan Hecht², Jürgen Rabe¹, and Stefan Kowarik¹ — ¹Humboldt-Universität zu Berlin, Institut für Physik — ²Humboldt-Universität zu Berlin, Institut für Chemie

Functionalized surfaces with molecules whose conformation can be reversibly switched between two isomeric forms by light are relevant for future devices -e.g. for switching adaptive materials, storing two states in memory applications, and switching current in molecular electronics. Here we use grazing incidence x-ray diffraction (GIXD), atomic force microscopy (AFM) and differential reflectance spectroscopy (DRS) to study light-induced structural changes in spin-coated thin films of Azobenzene-polymers with Alkyl side-chains. In solution, the individual Azobenzene-polymer shrinks upon UV-irradiation. Sub-monolayers of Azobenzene-polymers on Silicon oxide are still switchable with high efficiency, but do not show the same shrinking behavior, as suggested by AFM measurements before and after UV-illumination. Increasing the thickness to multilayers drastically changes the switching behavior, because of strong sterical hindrance. Interestingly, GIXD shows that the in-plane Bragg peaks corresponding to the coherent ordering of the Alkyl side-chains disappear when the sample is illuminated with UV-light and partially reappear after a few minutes in the dark, showing that switching is still possible in the crystalline state albeit with slower kinetics.