Regensburg 2007 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 18: Photonic crystals I
HL 18.5: Talk
Tuesday, March 27, 2007, 11:45–12:00, H13
Fabrication of silicon inverse woodpile photonic crystals — •Martin Hermatschweiler1, Martin Wegener1,2, Geoffrey Allen Ozin3, Alexandra Ledermann2, and Georg von Freymann2 — 1DFG-Center for Functional Nanostructures (CFN) and Institut für Angewandte Physik, Universität Karlsruhe (TH), 76131 Karlsruhe — 2Institut für Nanotechnologie, Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, 76021 Karlsruhe — 3Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
We fabricate silicon inverse woodpile structures for the first time. Direct laser writing of polymeric templates and a novel silicon-single-inversion procedure [1] lead to structures with gap/midgap ratios of 14.2% centered at 2.5 μm wavelength.
First, polymer templates are fabricated by direct laser writing or other means. Next, we deposit a thin silica coating via atomic layer deposition (ALD) on the polymer and - without removing the polymer - infiltrate the composite structure with Si via Si chemical vapor deposition (CVD). The silica shell provides sufficient and reliable stabilization for the high temperature CVD process. Finally, the silica is etched out and the polymer is calcined in air, leading to a Si inverse woodpile structure. Optical measurements and comparison to band-structure and scattering-matrix calculations reveal a gap/midgap ratio of 14.2% centered at 2.5 μm. An optimized structure could open a band gap with a gap/midgap ratio of up to 20.5%.
[1] M. Hermatschweiler et al., submitted (2006).