Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 29: Crystallisation, Nucleation and Self assembly

CPP 29.3: Vortrag

Mittwoch, 28. März 2012, 16:00–16:15, C 243

Lattice orientation, defects, and optical diffraction of opal-type photonic crystals — •Mulda Muldarisnur, Parvin Sharifi, and Frank Marlow — Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany

A systematic investigation on SEM images reveals that the capillary deposition method (CDM) [1] results in opal films with specific orientations which are interesting photonic crystals [2]. The orientation of the (111) fcc plane parallel to substrate is typical for many opals. However, opal orientation in respect to the growth direction is specific for a certain class of growth methods and indicates a decisive influence of the suspension flow during opal formation. The nearly perfect surface and the oriented lattice allows the existence of two crystal parts (intergrowths) having a certain misfit. The lattice misfit induces disordered boundaries and defects. We found that scattering by these and other defects can be described using Mie-like scattering. Recent angle-resolved transmission measurements and microscopic observations support the existence of two fcc domains in CDM-made opals. We observe well-resolved high-order diffraction peaks indicating opals with high quality. We can very well describe the rich features in the angle-resolved spectra by using the kinematical diffraction theory. Furthermore, intensity variation with angle can be described by using a simplified dynamical diffraction theory.

References: [1] H.-L. Li, W. Dong, H.J. Bongard, F. Marlow, J. Phys. Chem. B 109, 9939 (2005). [2] M. Muldarisnur and F. Marlow, J. Phys. Chem. C 115, 414 (2011).