Caltech, UCLA build blood cell-sized memory device

February 2, 2007 – Researchers at Caltech and UCLA recently said they have built a 16Kbit memory circuit with a footprint roughly the size of a white blood cell, providing insights into molecular-scale manufacturing, though they acknowledge such a device is years away from commerciality.

“It’s the sort of device that Intel would contemplate making in the year 2020,” assuming adherence to the pace of Moore’s Law lets them catch up to this particular device’s density, noted Caltech prof. James Heath. But he added that conventional chip manufacturing will run into red-brick walls probably beyond the year 2013, so it’s not certain at what point this new memory circuit could be put into, say, a laptop — “but we have time,” he added. “At the moment it furthers our goal of learning how to manufacture functional electronic circuitry at molecular dimensions.”

The 0.0408 µm2 device arranges the memory bits in a crosshatch architecture (400 silicon wires crossed by 400 titanium wires), with each 15nm-wide crossing representing a bit (vs. 140nm for current memory devices). In between each bit is a layer of [2]rotaxane molecular switches comprised of a molecular ring and a dumbbell-shaped molecule. When electronically triggered, the ends of the dumbbell display different conductivities, and the ring slides between the two locations.

The circuit — which researchers say can store the Declaration of Independence with space left over — has a bit density of 100Gb/cm2, which researchers say is a record for integration density in a manmade object. They could boost that to nearly 1000Gb/cm2, though after that “you begin to run out of molecules,” stated co-lead study author Jonathan Green, a Caltech graduate student in chemistry and applied physics.

The work was published in the January 25 issue of the journal Nature.


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