The team initially developed a method that allowed them to create precise electrical contacts with molecules in strong optical fields and to control them using an applied voltage. At a potential difference of around one volt, the molecule changes its structure: It becomes flat, conductive and scatters light.
This optical behaviour, which differs depending on the structure of the molecule, is known as Raman scattering and, in this case, was switched on and off via an applied voltage.
The researchers used molecules synthesized by teams based in Basel and Karlsruhe. The molecules can change their structure in specific ways when they are charged. They are arranged on a metal surface and contacted using the corner of a glass fragment with a very thin metal coating as a tip.
Serving as an electrical contact, light source and light collector, all in one. the researchers were able to use the fragment to direct laser light to the molecule and measure tiny spectroscopic signals that vary with the applied voltage.
Contacting individual molecules electrically is extremely challenging from a technical point of view, but eh scientists have been able to successfully combine this procedure with single-molecule spectroscopy, allowing them to observe even the smallest structural changes in molecules with great precision.
One goal of molecular electronics is to develop novel devices that can replace traditional silicon-based components using integrated and directly controllable molecules.
Due to its tiny dimensions, this nano-system is suitable for applications in optoelectronics, in which light needs to be switched using variations in electrical potential.