High temperature nanorelay for memory in power systems
Researchers at the University of Bristol have developed a new type of electromechanical nanorelay to enable reliable high-temperature, non-volatile memory in power systems.
As transistor leakage current increases with temperature, the nanorelay have emerged as a promising alternative to transistors. However, until now, a reliable and scalable non-volatile relay that retains its state when powered off, to implement memory, has not been demonstrated.
The work, reported in Nature Communications, was carried out in collaboration with the University of Southampton and the Royal Institute of Technology, Sweden. The team developed a nanorelay as a non-volatile memoy which worked over 42 cycles at 200 °C and retained data for up to six months.
“Part of the challenge is the way electromechanical relays operate; when actuated, a beam anchored at one end moves under an electrostatic force. As the beam moves, the airgap between the actuation electrode and beam rapidly reduces while the capacitance increases,” said Dr Dinesh Pamunuwa, the lead investigator at the University of Bristol. “At a critical voltage called the pull-in voltage, the electrostatic force becomes much greater than the opposing spring force and the beam snaps in. This inherent electromechanical pull-in instability makes precise control of the moving beam, critical for non-volatile operation, very difficult.”
The rotational nanorelay (above) maintains a constant airgap as the beam moves, eliminating this electromechanical pull-in instability. The nanorelay operates with an actuation voltages as low as 1.6 V with a 120 nm actuation airgap.
“This is a truly exciting development as the need to develop technology that reduces our dependency on fossil fuels increases. This relay operation is a significant step forward in developing electronics for all-electric vehicles and energy-efficient more-electric aircraft, as well as for creating zero-standby power intelligent nodes for the IoT,” said Pamunuwa.
“Electronics built from nano relays instead of transistors can work at much higher temperatures while also having zero standby power. Any digital electronic system needs logic and memory, and this relay makes it easier to build relay-based memory that retains the stored state when powered off, by using stiction. Maintaining a constant airgap as the relay switches allows very precise electrostatic control, and greatly improves reliability,” added Pamunuwa.
The relays were designed by Dr. Sunil Rana and nanoscale prototypes were fabricated by Dr. Joao Mouro, both senior postdoctoral researchers in the Microelectronics group at the University of Bristol. Dr. Jamie Reynolds, a senior postdoctoral researcher at the University of Southampton carried out contact material deposition at the Southampton Nanofabrication Centre, testing and characterisation under Professor Harold Chong’s supervision. Microscale prototypes were fabricated by Dr. Simon Bleiker of the Royal Institute of Technology.
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