Processors in computers and mobile phones, for example, contain billions of tiny switches known as transistors. Can't get any smaller? It is possible, and more than a thousand times faster, says Oldenburg physicist Martin Silies. He won a competition organised by the Federal Ministry of Education and Research with his idea for an optical transistor and now heads his own junior research group.
His experiments are invisible to the naked eye and even to some conventional microscopes: Dr Martin Silies is planning a transistor on the smallest conceivable scale, in which a single molecule determines whether a single light particle overcomes the distance between two miniature gold antennae and thus closes the switch or whether it opens again. And all of this happens unimaginably quickly, within trillionths of a second - smaller, finer, faster is the goal.
To further his research, the postdoctoral researcher in Prof Dr Christoph Lienau's "Ultrafast Nano-Optics" (UNO) working group at the Institute of Physics will now have his own junior research group with two doctoral positions. The funding period in the "NanoMatFutur" programme of the Federal Ministry of Education and Research (BMBF) is four years and can be extended to six years if required. Silies will initially have around 1.3 million euros at its disposal for the next four years.
We encounter transistors in every electronic device in everyday life. These electronic switches are now so small that they can be accommodated billions of times on a single processor. However, they cannot be made any smaller - or faster thanks to smaller components. The speed of these transistors has so far been limited to a clock frequency of a few gigahertz - i.e. a few billion switching operations per second.
Silies' research could increase the clock frequencies by a factor of more than a thousand and thus significantly speed up the work of mainframe computers, for example. His plan is to control individual particles of light, known as photons, in such a targeted way that they can be used to operate an optical transistor. The distance between the tips of two wafer-thin gold wires running towards each other is just a few millionths of a millimetre. Whether a photon overcomes these few nanometres - and thus closes the switch - is controlled by molecules that allow the photon to pass through or block it, depending on their own light saturation. The light saturation of the molecules can also be controlled with light at an unimaginable speed.
Over the next four years, the 35-year-old Silies and his doctoral candidates plan to test the interaction of various dye and other molecules on this smallest possible spatial scale. Before that, the team will be working on the most filigree gold contacts imaginable, which will be produced using a new technique - helium ion lithography. In this process, a beam of helium ions first cuts the fine wires from a wafer-thin gold film and then carves the finest lines into them. These lines act as signposts for the photons, so to speak, and guide them in the desired direction.
Earlier gold antennas for such photonic switches were produced by physicists using gallium-ion lithography. As helium ions are significantly smaller, they can now be used to produce much more delicate structures. Silies: "In relation, the gallium ions act like a cannon - the helium ions cut more slowly, but are comparable to a scalpel." For his research, he is working with Carl Zeiss Microscopy GmbH, the only manufacturer of helium ion microscopes in the world to date.
Such co-operations are welcome in the BMBF programme, which aims to develop new interdisciplinary approaches in nano and materials technologies that also hold potential for industrial implementation. The "NanoMatFutur" competition funds a maximum of seven junior research groups nationwide each year, particularly in the research fields of climate/energy, mobility, health or information and communication.
The new Oldenburg junior research group leader Silies studied physics at Steinfurt University of Applied Sciences. He completed his doctorate at the University of Münster in 2009 on so-called time-resolved X-ray diffraction - which also involved ultrafast interaction processes between light and other matter. Silies has been a member of the UNO research group in Oldenburg since 2009, where he is one of five postdoctoral researchers.
