ReRAM memory chip (credit UCL/Adnan Mehonic)

Researchers develop new silicon memory chip

Researchers say they have opened up the possibility of super-fast memory with an innovative new silicon memory chip.

The Resistive RAM (ReRAM) memory chip is based on materials, most often oxides of metals, whose electrical resistance changes when a voltage is applied – and they “remember” this change even when the power is turned off.

The team at UCL say the ReRAM chips, which can operate in ambient conditions, promise significantly greater memory storage than current technology, such as the Flash memory used on USB sticks, and require much less energy and space.

“Our ReRAM memory chips need just a thousandth of the energy and are around a hundred times faster than standard Flash memory chips,” said Dr Tony Kenyon, UCL Electronic and Electrical Engineering.

“The fact that the device can operate in ambient conditions and has a continuously variable resistance opens up a huge range of potential applications.

“We are also working on making a quartz device with a view to developing transparent electronics.”

The structure of the ReRAM chip is composed of silicon oxide, described in a recent paper in the Journal of Applied Physics, which performs the switch in resistance much more efficiently than has been previously achieved.

In their material, the arrangement of the silicon atoms changes to form filaments of silicon within the solid silicon oxide, which are less resistive.

The presence or absence of these filaments represents a ‘switch’ from one state to another.

The team’s new ReRAM technology was discovered by accident whilst engineers at UCL were working on using the silicon oxide material to produce silicon-based LEDs.

During the course of the project, researchers noticed that their devices appeared to be unstable.

UCL PhD student, Adnan Mehonic, looked at the material’s electrical properties and discovered that the material wasn't unstable, but flipped between various conducting and non-conducting states very predictably.

Devices operating in this way are known as ‘memristors’, and the development of a silicon oxide memristor is a huge step forward because of the potential for its incorporation into silicon chips.

“My work revealed that a material we had been looking at for some time could in fact be made into a memristor,” said Mehonic, at the UCL Department of Electronic and Electrical Engineering.

“The potential for this material is huge. We can programme the chips using the cycle between two or more states of conductivity.

“We’re very excited that our devices may be an important step towards new silicon memory chips.”

The ReRAM chip can be designed to have a continuously variable resistance that depends on the last voltage that was applied - an important property that allows the device to mimic how neurons in the brain function.

Unlike other silicon oxide chips currently in development, the chip does not require a vacuum to work, and is therefore potentially cheaper and more durable.

The design also raises the possibility of transparent memory chips for use in touch screens and mobile devices.

The researchers, who have filed a patent on the device, are also exploring using the resistance properties of their material not just for use in memory but also as a computer processor.

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