An international team of physicists, under the leadership of the Technical University of Munich, has succeeded in switching special molecules between two different structural states by the application of a voltage. Such 'nano switches' could form the foundation of a new type of component, not based on silicon, but instead based on organic molecules.

The development of new electronic technologies is necessary for a continuation of the reduction in size of the functional components. In Munich they succeeded in using a single molecule as a switch for optical signals.


Different structure ― different characteristics

The team first developed a technique that made it possible to make electrical contact with a single molecule, and subsequently control that molecule with an electric potential. At a voltage of about 1 V the structure of the molecule changes: it becomes flat, conductive and scatters light.

This change in optical behaviour of the molecule depending on its structure, is very exciting for the researchers: not only can the scattering of light (Raman scattering) be observed, but can also be deliberately turned on and off.
 

Technical challenge

For the switch the researchers used molecules that were especially synthesised by teams from Basel and Karlsruhe. These molecules are attached to a metal surface; the electrical contact is provided by the point of a glass fragment with a very thin metal coating. This glass fragment serves both as electrical contact and optical waveguide. The researchers were able to sense the minuscule changes in spectroscopic signals as a function of the applied voltage.

It is a real challenge to make electrical contact with a single molecule; the researchers succeeded in combining this technique with the spectroscopy of a single molecule.


Competition

One of the goals of molecular electronics is to develop new components and replace conventional silicon components with integrated and directly controllable molecules. Because of the very small dimensions, this nano system is eminently suitable for applications in opto-electronics where light is switched using electric signals.

The research has been published in the Journal of the American Chemical Society.