Regensburg 2007 – scientific programme
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DS: Fachverband Dünne Schichten
DS 7: Organic Film Aging (SYOE 3)
DS 7.4: Talk
Monday, March 26, 2007, 18:45–19:00, H32
Structural and desorption measurements on encapsulated rubrene thin films — •Maximilian Nothaft1, Silke Goettling2, Gerhard Ulbricht3, and Jens Pflaum1 — 13. Phys. Inst., Univ. Stuttgart, 70550 Stuttgart, Germany — 2Inst. fuer Systemtheorie und Bildschirmtechnik, Univ. Stuttgart, 70569 Stuttgart, Germany — 3Max-Planck-Institut fuer Festkoerperforschung, 70569 Stuttgart, Germany
FET-measurements on the surface of rubrene single crystals yield high room-temperature hole mobilities in the order of 10 cm2/Vs. However, it proves to be difficult to grow crystalline films by thermal evaporation because of molecular conformational changes [1]. As an approach to achieve a crystalline phase via thermal activation, structural properties of rubrene thin films capped by SiO2, Al2O3 and PPX have been investigated by x-ray diffraction. Crystallisation of amorphous rubrene capped with SiO2 was detected at about 155∘C which is 50∘C above the desorption point of uncapped rubrene layers.
In order to obtain information about the integrity of capped organic layers during heating, we performed thermal desorption studies on capped rubrene thin films. The data indicated different desorption mechanisms depending on the capping material. Desorption of rubrene in SiO2 or Al2O3 capped samples is mainly dominated by cracks. In contrast, desorption of PPX capped samples is governed by a diffusion process. Developing a suited model we could estimate the diffusion constant of rubrene in PPX to 1.2 · 10−10 cm2/s.
[1] Käfer et al., Phys. Chem. Chem. Phys. 7, 2850 (2005)