Regensburg 2007 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 17: Poster Session I (Nanostructures at Surfaces; Metal Substrates: Epitaxy and Growth; Methods: Scanning Probe Techniques; Phase Transitions)

O 17.85: Poster

Montag, 26. März 2007, 17:30–20:30, Poster C

Transmission increase upon switching of VO2 films on micro-structured surfaces — •Stephen Riedel¹, Ismael Karakurt², Johannes Boneberg¹, Paul Leiderer¹, and Richard Haglund³ — ¹Fachbereich Physik, Universität Konstanz, Fach M676, 78457 Konstanz — ²Department of Physics, Isik University, Maslak, Istanbul , Turkey — ³Department of Physics and Astronomy, Vanderbilt University , 6301 Stevenson Center Lane, Nashville TN 37235-1807, USA

Vanadium dioxide is one of the most-studied transition metal oxides due to its reversible thermochromism. It shows a semiconductor-metal phase transition occurring at a critical temperature Tc of 68 oC. The material is a semiconductor below the critical temperature while above Tc it is a metal. The Optical properties of the oxide, as well as the electrical properties, change upon the phase transition. The transmission through VO2 films decreases dramatically in the metallic state in the infrared region. We prepare VO2 films on different substrates (smooth glass substrates and on spherical SiO2 colloidal monolayers) and compare their switching behaviour upon heating with a ns-pulsed Nd:YAG-laser at 532nm. The observed behavior of the films on the two substrates is qualitatively different: while the smooth layers show the expected transmission decrease, the film on the micro-structured surfaces exhibit an increase in transmission when heated. We show that this at first glance unexpected behaviour can be explained by the additional contribution of diffraction which also changes at the phase transitions.