Istituto dei materiali per l'elettronica ed il magnetismo     
Tonezzer M., Toccoli T., Gottardi S., Bettotti P., Pavesi L., Iannotta S. Oligothiophenes thin films grown by SuMBD: the influence of kinetic energy on sub-monolayer formation. In: ECOSS26 - 26 European Conference on Surface Science (Parma, 30 Aug - 4 Sept 2009). Abstract, p. 66. European Physical Society, 2009.
A critical question in realizing organic devices with good performance is the presently limited ability in controlling growth, a factor that strongly affects the structure, morphology, physical/chemical properties in the solid state and the interfaces formation. Deposition methods based on vacuum sublimation give the best results in terms of film quality, but are still far fromthe desirable performance. These growth approaches typically control thermodynamic parameters at equilibrium, so they can hardly drive towards single phase structures organized at the needed length scale and in particular produce the layer-bylayer growth. SupersonicMolecular BeamDeposition (SuMBD) has shown to be uniquely suitable to approach such questions, achieving unprecedented control onmorphology and structure. This technique, based on supersonic beams of organics seeded in lighter carrier gasses, permits to overcome some thermodynamic limitations and opens new perspectives in realizing structures controlled at different length scales. In a recent work [Y. Wu, et al. Phys. Rev. Lett., 98 (2007) 076601] we have shown the key role played by the kinetic energy (Ek) of pentacene impinging molecules in controlling and determining the morphology and structure of the island growth right from the early stages. Here we report the results achieved growing different oligothiophenes by SuMBD. The morphological (AFM), structural (XRD) and optical characterizations show the high quality of the films deposited by SuMBD and its ability to control the film formation, starting from the sub-monolayer, as a function of the deposition parameters. The Ek of the impingingmolecules controls themechanisms of their surface diffusion and the critical number of molecules needed for island formation. Furthermore we report the electrical characterization of FET realized with these films, showing good electrical properties with optimal carrier mobility.
Subject Supersonic Molecular Beam Deposition

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