Berlin 2008 – scientific programme

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DS: Fachverband Dünne Schichten

DS 30: Layer Properties: Electrical, Optical and Mechanical Properties

DS 30.1: Talk

Thursday, February 28, 2008, 09:30–09:45, H 2032

Spectral ellipsometry of embedded VO₂ nanoclusters in SiO₂ during the semiconductor-metal transition — Helmut Karl, •Anne-Kathrin Jambreck, and Bernd Stritzker — Institut für Physik, Universität Augsburg, D-86135 Augsburg

Vanadium dioxide exhibits a semiconductor-metal transition at 68^∘C. We have synthesized VO₂ nanoclusters embedded in 200 nm thick thermally grown SiO₂ on 4-inch silicon wafers by ion implantation. The elements V and O were implanted with an energy of 100 keV and 36 keV respectively in order to place the maximum concentration to a depth of approximately 100 nm in the SiO₂ thin film. The fluences of V and O were varied between 10¹⁷ and 4x10¹⁶ at./cm² in order to achieve different V to O ratios and concentrations by a combinatorial ion implantation technique. After the implantation process the formation of the VO₂ nanoclusters was obtained by an annealing step in a rapid thermal processor in flowing Ar at 1000^∘C for 10 min. The formation of VO₂ precipitates was verified by Raman spectroscopy and x-ray diffractometry. The temperature dependent optical properties of the thin films were analysed by ellipsometry in the spectral range of 320 to 1700 nm. It was found, that the hysteresis of the optical parameters during the semiconductor-metal transition like refraction index n and extinction coefficient k as a function of temperature is much larger than that observed for VO₂ single crystals and thin films.