Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 12: Poster I

HL 12.33: Poster

Montag, 8. März 2004, 16:30–19:00, Poster A

Characterization and Structure Determination of Mesoporous Silica Films for Optical Applications — •Denan Konjhodzic¹, Markus Schmidt², Helmut Bretinger¹, Manfred Eich², and Frank Marlow¹ — ¹Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim an der Ruhr — ²TU Hamburg-Harburg, D-21077 Hamburg

Mesoporous silica thin films were synthesized in a sol-gel process using a nonionic triblock copolymer PEO-PPO-PEO as a template. Due to high pore volume of these films, the effective index of refraction is very low (n=1.14 at 1300 nm determined by the prism coupling method). Because of their high mechanical, chemical and thermal stability, high optical transparency, low optical scattering and especially because of the very low refractive index, these films are useful as substrates for 2D photonic crystals.

SAXS diffraction patterns obtained with an area detector clearly show a partially ordered structure of the channels in one type of as-synthesized films with a spacing of about 8 nm. There is no preferred direction of the channels parallel to the surface, which is in agreement with optical measurements. Other types of pore ordering have also been found. Calcination leads to the shrinkage of the structure. Surface properties have been investigated using AFM. The film surface is very smooth (roughness below 1 nm) but with certain defects in one structure type.

Based on these findings we propose structure models for our mesoporous films and for the defects inside. We discuss their implications for photonic crystal research.