Monday, May 16, 2011

#CHIPS: "HP discovers memristor mechanism"

Electrical engineers who expressed skepticism that Hewlett Packard Co.'s memristors could switch as fast as DRAM and yet retain their memories millions of times longer than flash can now rest easy, according to HP who cited new experimental results.

Synchrotron x-rays probed the memristor in a 100 nanometer region with concentrated oxygen vacancies (right, shown in blue) where the memristive switching occurs. Surrounding this region a newly developed structural phase (red) was also found to act like a thermometer revealing how hot the device becomes when read or written.

Using their favorite formulation—titanium oxide—HP used a synchrotron x-rays to correlate the device's electrical characteristics with its atomic structure, chemistry, and temperature in three dimensions. The until now unforeseen conclusion was that a hot spot near the bottom electrode heats enough during switching to induce a crystallization of the oxide. After driving out vacancies (for a 1) or introducing them (for a 0) in one-to-two nanometers thick region, the film cools in an annealing-like like process which leaves the film in a fixed crystalline state that should remain that way indefinitely.
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