Dresden 2014 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 20: Nanostructures at Surfaces II
O 20.6: Vortrag
Montag, 31. März 2014, 17:15–17:30, WIL B321
From insulator to conductor: infrared reflectivity of inverted fishnet designs — •Stefano De Zuani1, Marcus Rommel2, Helga Kumric1, Audrey Berrier1, Jürgen Weis2, Bruno Gompf1, and Martin Dressel1 — 11. Physikalisches Institut and Research Center SCoPE, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany — 2Max Planck Institute for solid state research, Heisenbergstrasse 1, 70569 Stuttgart, Germany
Metallo-dielectric nanocomposites at the insulator-to-metal transition show a discontinuity in their static conductivity and real permittivity in the infrared region that can in principle be described by percolation theories, assuming a random distribution of the metallic inclusions inside the insulating matrix. But what happens in ordered structures when random percolation is suppressed? We perform a systematic study on nearly closed, 20 nm thick gold films made of periodically arranged gold squares of size a separated by 10 nm gaps on a dielectric substrate. We perform reflectivity and spectroscopic ellipsometry investigations from the visible to the infrared range, increasing the gold filling factor f by changing the size of the squares a from 100 to 3600 nm. Our measurements reveal that square arrays with f around 0.9 exhibit a strongly decreasing reflectivity in the near-infrared range when a is decreasing. Solving Maxwell's equations under the full 3D boundary conditions leads to a reasonable agreement between theory and experiment. Regions of very large near-field enhancement in the gaps can be seen over a large frequency range and are responsible for the trapping of the incident light in the patterned structure.