Regensburg 2016 – wissenschaftliches Programm
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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: Vortrag
Mittwoch, 9. März 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 1st and 2nd 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 2nd 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.