Berlin 2008 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 23: Poster session
MM 23.41: Poster
Dienstag, 26. Februar 2008, 14:45–18:00, Poster B
Electric field controlled metal-oxide transformation of metal nanowires — •Carsten Nowak1, Guido Schmitz2, and Reiner Kirchheim1 — 1Universität Göttingen, Institut für Materialphysik, D-37077 Göttingen — 2Universität Münster, Institut für Materialphysik, D-48149 Münster
Under high electrostatic fields E, tip-shaped metal nanowires transform into the corresponding oxide at room temperature if a certain partial pressure p of water is present. A TEM investigation of this reaction was performed on nanowires of tungsten and aluminum as well as silicon.
The oxidation reaction starts at a critical field strength Ec(p) of the order of 109 V/m and proceeds until a quasi stationary state is reached. The kinetics of the reaction is gas supply-limited for pressures below 10−3 mbar and proceeds with rates corresponding to a diffusion coefficient of the order of 10−15 m2/s for a vapor pressure in the 10 mbar range, indicating driven diffusion.
Determination of the the electric field distribution inside the oxide using the finite element method and the results of current measurements during the oxidation reaction indicate that the critical step of the oxidation process is a surface reaction at the oxide-vapor interface. A quantitative model describing the observed Ec(p) dependence is given.