This post originally appeared as a news story in the September 2013 issue of Materials Today – can be accessed here (free for a limited time): http://digital.materialstoday.com/
Electrical switches made with magnetite have been shown to be thousands of times faster than the silicon transistors now in use, according to researchers with the U.S. Department of Energy (DOE).
Magnetite, a naturally-occurring magnetic material known for thousands of years has thrown up a surprise – a team from the U.S. Department of Energy’s (DOE) SLAC National Accelerator Laboratory has used it to produce the fastest-known electrical switch, which vastly outperforms the switching achieved in today’s standard silicon transistors.
It is hoped that this work, published in Nature Materials 1, will enable the development of a new generation of high-speed, high-efficiency transistors, leading to more powerful computational devices. The team from SLAC, led by Roopali Kukreja, collaborated with groups across Europe to measure the “speed limit” for electrical switching in magnetite. They discovered that it takes just a picosecond to flip the on/off electrical switch in magnetite, making it thousands of times faster than in transistors now in use.
In 2011, another research team 2 showed that in its insulating state, magnetite has electronic charges locked into structures known as ‘trimerons’, consisting of three iron atoms. To break this structure and force the material to become conductive, the SLAC team used the Linac Coherent Light Source (LCLS) x-ray laser to send pulses of visible laser light at the cryogenically-cooled mineral. This was shown to fragment the magnetite’s trimerons, rearranging them to form insulating ‘islands’ surrounded by electrically conducting regions.
Following these optical laser pulses, the magnetite was subjected to an ultra-bright, ultra-short X-ray pulse from the LCLS. By slightly adjusting the interval of the X-ray pulses, the team could precisely measure how long it took the material to shift from a non-conducting to an electrically conducting state. They could also observe the structural changes during the switch, and demonstrate the coexistence of conducting and non-conducting states.
Kukreja has said that the next stage of the work is to look at more complex materials and room-temperature applications. The researchers have conducted follow-up studies focusing on a hybrid material that exhibits similar ultrafast switching properties at near room temperature, but further work is needed. It is hoped that these results will drive innovations in the development of new highly-efficient transistors that can be used to tune the flow of electricity across nanoscale chips, enabling faster, and more powerful computing devices.
1: Nature Materials (2013) DOI: 10.1038/NMAT3718
2: Nature (2011) DOI: 10.1038/nature10704