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elctrnx_lyf
If the memristor is really capable of replacing both flash and DRAM in the ...
R G.Neale
Correction: the sentence in my comment above should read ...the memistor ...
HP discovers memristor mechanism
R. Colin Johnson
5/16/2011 5:31 PM EDT
PORTLAND, Ore.—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 their inventor, senior HP Fellow Stanley Williams.
"What we have discovered is that an electric field and a current act together to enable a memory device that can both be switched very rapidly and hold its state indefinitely," said Williams. "Not only does an applied voltage drive the migration of oxygen vacancies in the device, but at the same time there is a current that heats it up to about 300 degrees Celsius—just enough to turn the amorphous film into a crystalline film."
Memristors are touted as the future "universal memory" device because they are as fast as DRAM, as small as flash, and as durable as read-only-memories, according to HP. As the fourth fundamental passive circuit element—after resistors, capacitors and inductors—memristors retain either a high- or low-resistance state by virtue of introducing or removing oxygen vacancies in oxide thin films.
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 recently used high-energy 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.
"In testing, we have switched these devices over 30 billion times and counting, with no degradaton in their ability to retain information," said Williams.
HP is currently working with Hynix Semiconductor Inc. to create commercial memories based on memristive technology.
"What we have discovered is that an electric field and a current act together to enable a memory device that can both be switched very rapidly and hold its state indefinitely," said Williams. "Not only does an applied voltage drive the migration of oxygen vacancies in the device, but at the same time there is a current that heats it up to about 300 degrees Celsius—just enough to turn the amorphous film into a crystalline film."
Memristors are touted as the future "universal memory" device because they are as fast as DRAM, as small as flash, and as durable as read-only-memories, according to HP. As the fourth fundamental passive circuit element—after resistors, capacitors and inductors—memristors retain either a high- or low-resistance state by virtue of introducing or removing oxygen vacancies in oxide thin films.
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 recently used high-energy 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.
"In testing, we have switched these devices over 30 billion times and counting, with no degradaton in their ability to retain information," said Williams.
HP is currently working with Hynix Semiconductor Inc. to create commercial memories based on memristive technology.
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Phononscattering
5/16/2011 6:31 PM EDT
In the real world, the "memristor" is known as oxide based RRAM. There are numerous high profile publications in peer reviewed journals discussing the switching mechanisms.
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goafrit
5/16/2011 8:32 PM EDT
I have never known HP as the Bell Lab of 21st century. But they do can have surprises right now.
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R_Colin_Johnson
5/18/2011 7:14 PM EDT
HP is doing a good job of stepping up to the plate to fill the void in basic U.S. R&D.
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selinz
5/16/2011 9:27 PM EDT
This is interesting because it's not really noting any fundamental uniqueness of material properties but rather showing that known properties can be classified into a new category. See the presentations by Williams on You tube.. He is entertaining as well!
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prabhakar_deosthali
5/17/2011 7:51 AM EDT
Since such memories will be made of resistance banks ( whatever tiny size they may be) they could dissipate a lot of heat , I suppose. How is HP going to solve this heat dissipation problem?
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resistion
5/17/2011 11:33 AM EDT
A memristor would be an undesirable RRAM or PCM if it is one. By definition, reading it would alter its state due to charge passing through.
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R_Colin_Johnson
5/18/2011 7:12 PM EDT
There are various architectural features that can be used to enable reading RRAM bit cells made with memristors without changing their value.
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resistion
5/18/2011 9:59 PM EDT
But most if not all RRAM's other than HP's as well as PCM's, MRAM's, etc. do not exhibit such obvious sensitivities.
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R_Colin_Johnson
5/18/2011 10:09 PM EDT
HP is also planning to tune these sensitivities for analog operation, both to add levels for multi-bit per memristor storage, as well as for brain-like connections that become more conductivity the more you use them.
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resistion
5/18/2011 10:44 PM EDT
Colin, that is interesting to note, thanks. But for these analog operations, it is even more important to first confirm the distributions are tight. Otherwise relying on the sensitivities will lead to lots of errors.
Charges jump in and out all the time even at zero current. Should we expect natural memristance fluctuations?
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zhgreader
5/17/2011 9:36 PM EDT
breakout.
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bcarso
5/20/2011 2:46 PM EDT
I am glad that HP survived Fiorina, and now is showing that they didn't bite off more than they could Chua.
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R G.Neale
5/20/2011 7:18 PM EDT
Colin""""Not only does an applied voltage drive the migration of oxygen vacancies in the device, but at the same time there is a current that heats it up to about 300 degrees Celsius—just enough to turn the amorphous film into a crystalline film."""
So it now appears rather than just a device that uses voltage driven migration of vacancies to change the condition of a thin region, the memristor is a phase change is required, this is now another PCM a phase change memory. It needs a temperature of 300 C to crystallize, what temperature is required to return it to the amorphous state? Or how does it return to the amorphous state and is the formation of the crystalline state a one time initial forming process into which vacancies are forced or removed to create the memory states?
It will be interesting to see if the memory patent portfolio of ENER and or Ovonyx cover phase changes in materials other than chalcogenides and or materials in general, I suspect they might. If so HP might find they have more than a technology manufacturing problems to deal with.
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R G.Neale
5/21/2011 5:19 AM EDT
Correction: the sentence in my comment above should read ...the memistor requires a phase change, this is now just another PCM phase change memory.....
Apologies
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elctrnx_lyf
5/21/2011 2:31 PM EDT
If the memristor is really capable of replacing both flash and DRAM in the future, then definitely this is a welcome news for any product. I wish HP can commercialize this in the next couple of years.
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