| AVS 55th International Symposium & Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF-WeM |
| Session: | Chemical Vapor Deposition |
| Presenter: | J. Götzen, Ruhr-University, Germany |
| Authors: | J. Götzen, Ruhr-University, Germany D. Käfer, Ruhr-University, Germany Ch. Wöll, Ruhr-University, Germany G. Witte, Ruhr-University, Germany |
| Correspondent: | Click to Email |
Previous studies have shown that the structure of organic semiconductor film depends sensitively on the interaction with the substrate. In this respect we have studied the film growth of pentacene onto highly oriented pyrolytic graphite which constitutes an interesting model system for a chemically rather inert but - in contrast to amorphous oxides – highly ordered crystalline substrate. Here we report a comprehensive characterization of the microstructure, morphology and thermal stability of pentacene films grown by OMBD onto freshly cleaved HOPG by employing STM, AFM, NEXAFS, XRD and TDS. Despite a rather weak, essentially van-der Waals-type substrate interaction pentacene molecules adsorb with their planes oriented parallel to the surface and form a commensurate monolayer due to the close match of the molecular carbon frame and the underlying graphite lattice. This packing motive, however, is not maintained in multilayer films where instead molecules in subsequent layers are tilted around their long axis. The multilayer growth is further characterized by the formation of individual crystalline islands exhibiting the Siegrist bulk polymorphism for rather different growth conditions (rate and temperature) and thus parallels the growth scenario observed previously for pentacene on Au(111)1 In contrast films with upright oriented molecules were obtained if the graphite had been briefly sputtered before deposition and thus emphasizes the importance of micro-roughness on the resulting film growth.
1D. Käfer, L. Ruppel, G. Witte, Phys. Rev. B 75, 085309 (2007).