Excellent article! Thankyou, Mani.
Rather timely, too, seeing as it just came out today. It gives me a time perspective that I didn't have before, (and that you seem to have been right about).
I need to study this article and the Scientific American article some more, but it seems that the EE-Times article makes no mention of the "third" technology in the SA article which is being developed by Lienau at Micromem -- the one based on the Hall Effect. Johnosn (who handed a similar design over to Honeywell) thinks it could have a commercial impact in a couple years in the area of EEPROM's and Flash Memory. Granted, that's a far cry from becomming a substitute for main memory.
Those uncertainties may leave an opening for a third approach that has less money behind it, but more history. Edwin Hall discovered 120 years ago that a current moving through a thin film is deflected to one side by a magnet. Lienau's "magram" device exploits this effect, as does a similar design of Johnson's called a Hall effect hybrid memory.
Theoretically, both designs should be easier to manufacture than spin valves or tunnel junctions. They tolerate heat well. And Johnson notes that his design requires only half as many etching steps as DRAMs. Moreover, "unlike all other memories, [magram] can be deposited on glass--perhaps even plastic--instead of single-crystal silicon," Sadwick claims as he shows, during a visit by Scientific American, a glass slide covered in gold wires leading to a one-millimeter-square array of Hall effect sensors. That versatility should allow the memory to be cheap even if it cannot shrink to the submicron cell sizes of its competitors, he argues. With single cells already working, Sadwick says, "I see no reason why we can't get eight-bit commercial samples this year."
Johnson, meanwhile, has turned over his design to Honeywell, which has built one-micron test devices on gallium arsenide. "They can write bits in eight nanoseconds," he reports. The next generation, he says, will be smaller, faster and made atop silicon, the industry standard for microchips.
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