In the future, low-power electronics could benefit from the amazing properties of a well-known material. An EU project involving leading specialists now aims to reveal the last secrets.
First there was the word. Then the switch. And then the transistor. Another innovation could now continue the electronics story. Vanadium dioxide (VO2) – named after the Nordic god Vanadis – is set to take control of the flow of electrons. VO2 has long been known for its unique properties. Although at room temperature the crystal is transparent and an electrical insulator, at a temperature of 68 °C it turns into a light-reflecting electrical conductor. This “insulator to metal transition” is being investigated in detail because it could allow not only extremely fast but also very energy-efficient electronics. And this is more important than you might think. After all, the billions of IoT devices with today’s technology will consume around 20 percent of all global energy by 2025.
“Phase-Change Switch” is the name of an EU project which aims to reveal the secret surrounding VO2’s famous properties. Scientists from the Swiss Federal Institute of Technology in Lausanne (EPFL), Thales from France, IBM Research, the Max Planck Society, Cambridge University and Gesellschaft für Angewandte Mikro- und Optoelektronik (AMO GmbH) are involved in the project.
Order is not everything
It was discovered that at temperatures above 68 degrees Celsius the atomic structure of VO2 changes from a orderly crystal lattice into a disorderly metallic one. And this takes less than a nanosecond – a property which makes it ideal for electronic applications. However, VO2 reacts to other influences too. Its structure changes if a voltage is applied to it, if light shines on it or under the influence of terahertz waves.
However, there was always a catch with the wonderful properties of vanadium dioxide. The “transition temperature” of 68 degrees Celsius is too low for electronic circuits which have to work at temperatures of 100 degrees Celsius. Two EPFL researchers came up with a solution to the problem. By adding a certain amount of germanium, the phase transition temperature can be raised to 100 degrees Celsius. Scientists from the University of Jena used a different method around two years ago. Through ion bombardment, they controlled the transition temperature in any area of a VO2 crystal with an accuracy of around 20 nanometers.
Vanadium dioxide and autonomous vehicles
For the first time ever, the researchers from the EPFL were able to produce ultra-compact frequency filters using vanadium dioxide and phase change switches. The filters which are used for a space communications system can be modulated between 28.2 and 35 GHz. With its extraordinary switching properties, the material could also be used in neuromorphic computer systems for artificial intelligence applications and in autonomous vehicles.