Engineers at Ecole Polytechnique Fédérale de Lausanne (EPFL) have shown that the compound vanadium dioxide can be programmed to have radiofrequency electronic functions that could prove to be useful for aerospace communication systems.
Vanadium has four different oxides, but vanadium dioxide (VO2) is a dark blue solid and amphoteric oxide. It dissolves in acids to give the blue [VO]2+ vanadyl ion, but in alkalis, it provides a brown [V4O9]2− ion. Vanadium dioxides properties that make is so unique include beings a metal-insulator transition, behaving as an insulator at room temperature and a conductor at temperatures above 68°C.
VO2 is currently used for sensors, surface coatings, and imaging, but the unique properties of vanadium dioxide could be used to outperform current silicon devices. The research into VO2 could potentially create a new generation of low-power electronic devices.
The research is being carried out under the Phase Change Switch project, and a paper has been published recently about the work in IEEE Access. The potential implications of the research have been seen by both research councils and major companies, with €3.9 million of EU funding having been put towards the project until 2020. The project has piqued the interest of companies such as Thales France, IBM Research, AMO GmbH, Max-Planck-Gesellschaft and universities such as Cambridge University
The properties of VO2 are due to its changing atomic structure with temperature. VO2 transitions in less than a nanosecond from a crystalline structure at room temperature, to a metallic one at temperatures above 68°C. The speed of the structural change is seen to be a significant advantage for electronics applications, but the low transition temperature has proven difficult as it is too low a temperature for modern electronic devices that need circuits that can run smoothly at 100°C.
VO2 is also sensitive to other factors that could cause it to change phases, such as by injecting electrical power, optically, or by applying a THz radiation pulse
Adrian Ionescu, EPFL Professor - Nano-Electronic Devices Laboratory (Nanolab)
Professor Ionescu from the School of Engineering (STI) and Andreas Schüler from the School of Architecture, Civil and Environmental Engineering (ENAC), two EPFL researchers, published research in the Journal of Applied Physics in July 2017 that may have found a solution to this problem. They found that adding germanium to VO2 film means that the phase change temperature of the material can be lifted to over 100°C.
Now, scientists can make ultra-compact, modulable frequency filters. The new technology uses VO2 and phase-change switches, particularly effective in the frequency range crucial for space communication systems. It uses the Ka-band, with a programmable frequency modulation between 28.2 and 35 GH).
The discoveries have prompted further research into the possible applications for VO2 in ultra-low-power electronic devices. As well as the applications for space communications, other potential fields that are also big possibilities for the future that need further exploration include neuromorphic computing, artificial intelligence and high-frequency radars for self-driving cars.
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