Thermally and seed-layer induced crystallization in rubrene thin films

Abstract

We have analyzed the tendency of crystallization and the thermal activation of ordering processes in rubrene thin films. As we will demonstrate, a crystalline phase with a unit cell in agreement to the bulk structure can be stabilized upon heating of amorphous rubrene layers previously capped by a sputtered SiOx layer. This encapsulation significantly enhances the thermal stability of the organic film by about 150°C. We compared this approach with crystallization initiated by the presence of a pentacene seed layer during rubrene deposition. Thin film transistors prepared by this route showed hole mobilities of 0.01 cm2/Vs which are four orders of magnitude higher than for their amorphous counterparts. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.