Regensburg 2016 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 41: Crystallization, Nucleation, Self Assembly II (joint session CPP/DY, organized by CPP)

CPP 41.8: Talk

Wednesday, March 9, 2016, 18:15–18:30, H42

Coverage dependent nucleation of PTCDI-C₈ studied by AFM and in situ real time XRR and GISAXS — •Anton Zykov¹, Sebastian Bommel², Christopher Wolf¹, Linus Pithan¹, Christopher Weber¹, Paul Beyer¹, Gonzalo Santoro³, Stephan V. Roth², and Stefan Kowarik¹ — ¹Inst. f. Physik, Humboldt Universität Berlin — ²Deutsches Elektronen-Synchrotron DESY, Hamburg — ³Inst. de Ciencia y Tecnología de Polímeros, CSIC, Madrid

Assembly of molecular building blocks into functional nanomaterials is of great importance for devices however it is difficult to follow molecular scale morphology during growth. Here we show that modern synchrotron small angle X-ray scattering (GISAXS) and X-ray reflectivity (XRR) agree with post growth AFM measurements of roughness and island densities of PTCDI-C₈ on silicon oxide, but additionally offer in situ and real time capability. We observe interesting differences in the growth of the 1^st and 2^nd monolayer (ML) such as different molecular adsorption probabilities and a transition of the island shapes. From the scaling of saturation island densities with substrate temperature and growth rate we evaluate ML dependent nucleation energies and critical nucleus sizes. We discuss our results in the framework of nucleation theories and find that 2^nd ML nucleation does not proceed in the often applied diffusion limited aggregation regime. This work shows that X-ray techniques are similarly suited for continuously monitoring multilayer growth and unravel intricate details about sub-monolayer growth.