Berlin 2015 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: Organic Thin Films

CPP 12.1: Hauptvortrag

Montag, 16. März 2015, 15:00–15:30, H 2032

Thin film growth studies using time-resolved X-ray scattering — •Stefan Kowarik — Institut für Physik, Newtonstr. 15, 12489 Berlin

Thin film growth inherently is a non-equilibrium process. This means that the route to the final film structure is determined not simply by a minimization of the free energy, but by a non-trivial competition between thermodynamics and kinetics. For a quantitative understanding one therefore needs information on the nanoscopic surface processes such as molecular binding as well as surface diffusion and step-edge crossing. In situ X-ray scattering is ideally suited for such measurements as it can be used to monitor temporal changes on the atomic scale. We show how real-time in situ Grazing Incidence Small Angle Scattering (GISAXS) can be combined with simultaneous X-ray reflectivity measurements to characterize both in-plane and out-of-plane film structure as a function of time. While GISAXS gives information on nucleation densities and island sizes, reflectivity measurements make it possible to extract the out-of-plane density profile so that both measurements together give a rather complete morphological characterization. We give examples for growth of small-molecule organic semiconductors such as C60, where we determine diffusion barrier, step edge barrier and binding energy, but the techniques are equally applicable to growth of atomic systems. S. Bommel, N. Kleppmann, C. Weber, H. Spranger, P. Schäfer, J. Novak, S.V. Roth, F. Schreiber, S.H.L. Klapp, S. Kowarik, "Unravelling the multilayer growth of the fullerene C60 in real-time", Nature Communications 5, 5388 (2014).