Digital Memory Uses 100 Times Less Power


Let's be honest. Our phones are not just phones anymore. Nor are our computers just computers. Whether streaming videos on smartphones, Skyping on laptops or stashing our MP3s on both, the parameters and capabilities of our devices continue to grow as they meld into one and the same machine.

Unfortunately, all this multitasking is incredibly taxing on battery life. But researchers from the Electrical and Computer Engineering Department of the University of Illinois have developed a new form of low-power digital memory that could add longevity to the battery life of smartphones and laptops.

The Illinois research group developed this new form of memory using phase-change materials (PCM) that instead stores bits of memory in the resistance of the material itself, rather than storing bits as a charge. Each bit can be reversibly switched with voltage pulses and localized Joule heating.

Led by professor Eric Pop, the research group was able to lower the high programming current needed to successfully couple Joule heat to a finite bit volume. They achieved this by using the smallest known electronic conductors — carbon nanotubes — rather than using metal wires. Carbon nanotubes are 10,000 times smaller than a human hair and developed by chemical vapor deposition.

Nanogaps were created in the middle of the nanotubes, which span titanium/palladium metal contacts. A thin film of PCM filled the nanogaps when placed over the nanotube, creating self-aligned PCM bits.

A layer of SiO2 was deposited over on top of the PCM film, creating a device with prolonged switching lifetimes that is immune from from the deterioration often encountered with metal wires. This device is also safe from accidental erasure from magnets or passing scanners.

The device remains in "off" until voltage is applied to the nanotube, switching the PCM bit to "on." Because switching only occurs at the nanogaps, the current used was found to be two times lower than conventional PCM devices.

Feng Xiong recently told the University of Illinois News Bureau,"The energy consumption is essentially scaled with the volume of the memory bit. By using nanoscale contacts, we are able to achieve much small power consumptions." Xiong was the first author on the paper detailing this breakthrough.

This low-power, nanoscaled digital memory uses 100 times less energy than what is currently available in devices like smartphones and laptops, and could offer immediate resilience to the battery life of these electronic gadgets.

Image: Eric Pop, University of Illinois

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