Berlin 2018 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 58: Organic Thin Films, Organic-Inorganic Interfaces: Session I (joint session DS/CPP)

CPP 58.5: Talk

Wednesday, March 14, 2018, 17:30–17:45, H 0111

Anomalous Roughness Evolution of Organic Mixed Films — •Alexander Hinderhofer, Jan Hagenlocher, Martin Oettel, and Frank Schreiber — Institute of Applied Physics, University of Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany

The surface morphology and roughness of thin films and crystals depend on competing mechanisms, which either roughen or smooth the film surface during growth. Important roughening mechanisms, are kinetic roughening based on shot noise and roughening due to mound growth, which is facilitated by reduced interlayer transport, often associated with a step edge. While these issues have been well studied for growth of simple atomic species, comparatively little is known about organic systems. These are expected to exhibit a fundamentally different growth behavior, due to their different interactions (van-der-Waals) and thus different response to strain and due to their internal degrees of freedom.

We use in situ x-ray reflectivity and complementary atomic force microscopy to monitor crystallinity and roughness evolution during growth of organic binary mixtures of several compounds, i.e. pentacene (PEN), perfluoropentacene (PFP), diindenoperylene (DIP) fullerene (C60). A general trend of reduced roughness in the mixed films compared to the pure materials is observed. We will discuss this roughness evolution in relationship to the in-plane crystallinity of the thin films and will show that the growth behavior can be rationalized by a, compared to homoepitaxy, lowered step edge barrier for lower in-plane crystallinity.