Dresden 2011 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 22: Topical Session TEM VI
MM 22.6: Vortrag
Mittwoch, 16. März 2011, 12:45–13:00, IFW B
3D electron tomography of biological photonic crystals — •Benjamin Butz1, Benjamin Winter1, Benito Vieweg1, Isabel Knoke1, Stefanie Spallek1, Gerd Schröder-Turk2, Klaus Mecke2, and Erdmann Spiecker1 — 1CENEM, Universität Erlangen-Nürnberg — 2Theoretische Physik I, Universität Erlangen-Nürnberg
Photonic crystals, i.e. periodical nanostructures of materials with different dielectric constants, are highly interesting for applications in optics, optoelectronics, and sensing. By tailoring the geometrical parameters radically different and improved optical properties (e.g., optical band-gap structure, extreme refractive indices, or high anisotropy) can be achieved. Naturally occurring photonic crystals, like butterfly scales, exoskeletons of insects (chitin), or seashells (nacre), can serve as model systems for understanding the relationship between structure and optical properties. Butterfly scales are studied by TEM using a FEI Titan3 80-300 instrument. An optimized FIB technique or ultramicrotome sectioning were used to prepare the sensitive specimens with desired thickness. Since the periodical structures have dimensions on the sub-µm scale, HAADF-STEM tomography was employed for obtaining extended tilt series under conditions of atomic-number sensitive imaging. Since the solid crystal consists of chemically homogeneous chitin while the pores are unfilled, the distinct contrast in the images can easily be interpreted in terms of the local projected mass density allowing to reconstruct the chitin distribution within the optical unit cell of the scales with high 3D resolution.