Dresden 2006 – scientific programme

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DS: Dünne Schichten

DS 1: Optical properties of thin films I

DS 1.6: Talk

Monday, March 27, 2006, 10:45–11:00, GER 37

Optical properties of ultra-thin metal films at and below the percolation threshold — •Tobby Brandt, Bruno Gompf, Natalia Drichko, and Martin Dressel — 1. Physikalisches Institut der Universität Stuttgart

While the optical properties of thicker metal films are well understood, little has been done at and below the metal-to-insulator transition (percolation threshold), especially in the infrared region.

We present temperature dependent FTIR reflection measurements in the range 500 to 6000 cm⁻¹ on ultra-thin gold films grown on vicinal Si (111)(7x7) surfaces. The films with thicknesses between 9 nm and 0.4 nm were characterized in situ under UHV conditions between 300 K and 5 K.

The thicker films show normal Drude behaviour with an increasing reflectivity toward lower frequencies. At about 2 nm the metal-to-insulator transition is observed. Here the films show a nearly frequency and temperature independent optical conductivity. Below 2 nm a dielectric anomaly was observed with an inverted temperature characteristic. The data are analysed within the framework of the model given by D. Bedeaux and V. Vlieger [1], which has the advantage compared to effective medium theories, that it takes explicitly the interaction with the interface into account.

[1] D. Bedeaux and J. Vlieger ; No-dqOptical Properties of SurfacesNo-dq; Imperial Collage Press, 2001