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Electronically tunable nanomaterials

Horst Hahn 

Forschungszentrum Karlsruhe (FZK), Postfach 3640, Karlsruhe D-76021, Germany


The properties of materials are typically controlled in a static manner by the microstructure. This implies control of the grain size, defect concentration, structure and metastability. As long as the microstructure does not change during the use of the material, the properties of the material are fixed, or irreversible. In semiconducting materials, properties can be tuned by the application of an external field due to the space charge regions which extend far from the interfaces. In metallic systems, this effect cannot be observed unless the dimensions of the structures are in the nanometer regime. The reason for this different behaviour is the small spatial dimension of the space charge regions due to the effective screening of the induced charges by the conduction electrons. In nanoporous metals and thin films exposed to appropriate electrolytes, it has been demonstrated that substantial changes of physical properties can be induced by the application of a potential between the nanostructured metal and a counter electrode. Examples of the changes of surface stresses and the electrical resistivity of thin Gold films and nanoporous Gold will be presented. The experimental results can be interpreted by the modification of the electron density distribution at the interface of the metal and the electrolyte. Furthermore, results on the tunability of magnetic properties will be summarized. The extension of the concept to organic molecules whose properties can be switched by temperature or light will be discussed.


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Related papers

Presentation: Invited at E-MRS Fall Meeting 2007, Acta Materialia Gold Medal Workshop, by Horst Hahn
See On-line Journal of E-MRS Fall Meeting 2007

Submitted: 2007-06-01 08:30
Revised:   2009-06-07 00:44