Dresden 2009 – wissenschaftliches Programm
DS 9.4: Vortrag
Dienstag, 24. März 2009, 10:15–10:30, GER 37
Dielectric properties of ultra-thin metal films around the percolation threshold — •Martin Hövel, Martin Alws, Bruno Gompf, and Martin Dressel — 1.Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70550 Stuttgart, Germany
The dielectric properties of percolating metal films around the insulator-to-metal (IMT) transition are not well understood . By combining Fouriertransform infrared spectroscopy (FITR), spectroscopic ellipsometry, and dc-conductivity measurements on ultra-thin Au films on Si/SiO2 the effective dielectric properties around the IMT can be described Kramers-Kronig consistent over a very brought frequency range from 500 to 27 000 cm−1. Above a critical thickness dc, the so called percolation threshold, the films show for low frequencies a typical metallic-like behavior which can be fitted by a simple Drude-Model . Below dc the frequency behavior is dominated by a "Maxwell-Garnett resonance" which shifts to lower frequencies with increasing film thickness and dies out well above the IMT. A dielectric anomaly with a maximum of є1 at dc is observed and can be described by the interplay of this resonance and the onset of the Drude-component. Additionally the temperature dependence of the films were studied. Here also a transition from an activated to a metallic like behavior at dc was found.
 B. Gompf, J. Beister, T. Brandt, J. Pflaum, M. Dressel, Optics Letters 32, 1578 (2007)
 T. Brand, M. Hövel, B. Gompf, M. Dressel, Phys. Rev. B 78, 205409, (2008)