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arXiv · 0904.4335

Dielectric properties of ultrathin metal films around the percolation threshold

Martin Hövel·Martin Alws·Bruno Gompf·Martin Dressel
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Abstract

We report on optical reflection measurements of thin Au films at and around the percolation threshold (film thickness 3 to 10 nm) in an extremely broad spectral range from 500 to 35000 cm-1 (0.3 - 20 *10-6 m). Combining spectroscopic ellipsometry and Fourier-transform infrared spectroscopy, the dielectric properties of the films can be described over the whole frequency range by Kramers-Kronig consistent effective dielectric functions. The optical conductivity of the films is dominated by two contributions: by a Drude-component starting at the percolation threshold in the low frequency range and a plasmon in the near-infrared region, which shifts down in frequency with increasing film thickness. The interplay of both components leads to a dielectric anomaly in the infrared region with a maximum of the dielectric constant at the insulator-to-metal transition.

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Martin Hövel, Martin Alws, Bruno Gompf, Martin Dressel. 2009-04-28. Dielectric properties of ultrathin metal films around the percolation threshold. https://doi.org/10.1103/physrevb.81.035402

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