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New Memristor Makes Low-Cost, High-Density Memory
KentuckyFC writes "A group of electronics engineers have discovered that a thin layer of vanadium oxide acts as a memristor, the fourth basic component of circuits after resistors, capacitors, and inductors that was discovered last year. At a critical temperature, a current passing through the layer causes it to change from an insulating state to a metal-like state, thereby changing its resistance (abstract). The effect lasts many hours — which is what makes the layer a memristor (a resistor with memory). The team says this could be scaled up to make resistive random access memory, or RRAM, at very low cost, from little more than layers of vanadium oxide."
The article suggests use as resistive RAM rather than a solid state drive. As long as it doesn't need to be a permanent memory element it might be possible to refresh periodically on a schedule that's safely less than the lifetime of the state transition, i.e. boost the phenomenon every hour or two. Shouldn't cause much of a power hit.
I thought the more exciting announcement was that memristors could be tripled up to create transistors that were (despite being tripled up) still much smaller than a standard transistor.
Then, there were bits about them supporting more than just binary states, which would increase complexity and density yet again.
Denser memory may be the first pratical consumer product, but if the other possiblities work out, I'm pretty sure that memory will also be the least significant.
" At a critical temperature,"
"Gee, I had it stored on this memsistor chip - but I left it in my shirt pocket, and my data melted."
The article doesn't say what temperature, so there's probably an issue there. Until that issue is solved, it's about as useful as write-only memory.
Also, looking at the required voltage (50 volts @ 0.6 amp), this is NOT going to be either high-density, or portable,or particularly energy-efficient.
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I've seen this statement repeated about memristors. Many devices cannot be duplicated with L's, C's and R's (diodes, fuses, etc.). Those parts all have one thing in common, they are nonlinear and/or time varying. Memristors are not LTI and therefore not a "fourth type" of circuit element.
No more need to supercool RAM on seized computers in order to extract passwords - the RAM will just naturally hold state for hours.
If they're going to use this, (some) people are going to want to have more secure operating systems that don't leak security data all over the place.
http://en.wikipedia.org/wiki/Memristor#Potential_applications
[27] http://www.nytimes.com/2008/05/01/technology/01chip.html
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Not really; if you only have to refresh it once every four hours, you can do that for a LONG time on a battery. What I really see as the potentially big win is if they can get the speeds up to SRAM levels. Technically it would be a kind of DRAM, but if you only have to refresh it once every four hours, then just using a LRU scheme when allocating memory might mean that in practical usage you would never need a refresh anyway.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Yes. Resistance is fusile.
Kevin Smith on Prince
"Unlike those more familiar elements, the necessarily nonlinear memristors may be described by any of a variety of time-varying functions. As a result, memristors do not belong to linear time-invariant (LTI) circuit models. A linear time-invariant memristor is simply a conventional resistor." - Wikipedia
It's all about linearity.
Nothing to see here.
It differs in the fact that NTC and PTC resistance value depends on a current condition as where memristors resistance depends on a past event. In this example's case once the vanadium oxide becomes an conductor due to trigger voltage and current that trigger can be removed and it will remain a conductor for several hours. So you can see this is vastly different from NTC / PTC devices.
On a second thought, if one taps into the excess CPUs and GPUs heat. Still a bad fit for a mobile device though
extern warranty;
main()
{
(void)warranty;
}
Sorry to be so harsh, but the specific experiment reported here is of little to none value outside of science. Why?
Hysteretic resistive switching in metal oxide systems is a well known phenomenon (RRAM) and occurs in all transition metal oxides with noble eletrodes. This is what has been recristened as "Memrestor" by HP. It is widely agreed upon that this switching mechanism is due to a redox reaction where oxygen is added or removed from the insulator. The specifics (filament, interfacial barrier lowering etc.) are still subject of current research though.
The experiment in the paper takes a slightly different approach: vanadium oxide has a very interesting property where its resistance switches apruptly by orders of magnitude at a certain temperature due to a reorganisation of its electronic structure. This phenomenon is known as metal to insulator (MTI) transition and has been research for at least 50 years.
The MTI has a hysteretic behavior which means that it retains its state if you vary the temperature only a little above or below the critical MTI temperature Tc. The researchers have now shown that if you keep the temperature of the system close to Tc, you can use an additional electric current to switch the resistivity of the system. A possible explanation could be self heating.
Why is it useless for practical application?
1) The phenomenon instrinsically only works at a certain temperature. Deviations by fractions of degrees K will destroy all information.
2) As far as I can see they only demonstrated electrical switching into one direction. To erase the memory both would be required.
All in all a nice experiment, but again with typical university style hype, piggybacking on the Memristor craze.
I am also relatively certain that current driven MTI switching has been reported before. I am aware of a couple of experiments where a field switched MTI transition was proposed for transistors. Those devices should exhibit exactly the same hysteresis and "memory" properties.
i = current
q = charge
V = voltage
phi = magnetic flux
dq = i dt (current)
dphi = V dt (voltage)
dV = r di (resistance)
dq = C dv (capacitance)
dphi = L di (inductance)
(see http://www.spectrum.ieee.org/may08/6207)
It was hypothesized that some device should exist that connects charge and flux, and follows the relationship: dphi = M dq. This is "memristance." It was predicted in 1971 as the "fourth basic circuit element"; see: http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1083337
They were fundamentally theoretically new then. They just had not been physically realized and connected with that theory until recently.
Please don't dismiss them as "pure marketing hype" without some research.
The GP was commenting on the fact that a memristor is not linear time invariant element. So it isn't as basic as the other 3. The other three can be analyzed using fairly simple analysis, while the memristor seems to introduce state to a circuit.
Circuits that are time linear, and time variant are more difficult to analyze on a broad scope than those that are LTI.
So according to you,
V dt = dphi = L di?
Or is this wrong? And if yes, why?
P.S.: Slashdot, please fix your UTF-8 support! I have phi on my keyboard, but your system ignores it. And I also tried φ, which did not work either.
Any sufficiently advanced intelligence is indistinguishable from stupidity.
not been physically realized and connected with that theory until recently.
Actually that is not true. Resistive switching had been demonstrated even before 1971 (there are some examples on Wikipedia).
Let's see, what happened here?
1) Someone found resistive switching
2) Someone developed a trivial algebraic model of a resistor with a memory effect
3) Someone with good marketing skills and connections combines 1) and 2) and manages to ram a paper into Nature.
4) Lots of press hype ensues
5) Profit? nope. Novel? nope. Publicity? Way too much, given for the nonevent. Application? Was already there at 1) in form of RRAM.
Did anybody notice that a new class of high temperature superconductors was found recently? Or multiferroics? Or commercial availability of phase change memory (PCRAM), which may render RRAM obselete before it went anywhere?
So according to you,
V dt = dphi = L di?
Or is this wrong? And if yes, why?
Well... ...which is the standard formula they give for inductors, isn't it?
V dt = L di
(V dt)/dt = (L di)/dt
V = L di/dt
Or did I totally miss your point?
"You might think you turned your computer off and destroyed RAM contents"
Even for conventional RAM, most of the contents stay for quite a while after power loss. And the colder the chips are the longer the duration.
Try turning off your computer and then immediately booting something that lets you peek into the RAM.
See: http://www.freedom-to-tinker.com/blog/felten/new-research-result-cold-boot-attacks-disk-encryption
I think the GP was doing his or her math homework, and you just gave him/her the answer to the extra-credit question. :-)
. . . just posting this in the very unlikely chance that a competent USPTO employee (I know you're out there) is not only reading this thread but also is assigned related patents.
IMHO this kind of development is worthy of a patent; it includes a brand-new type of component, with no prior art in a single component appearing to exist, and a method by which it is manufactured.
Now, I expect patent trolls will start the patenting insanity with "it's a PDA, but with memristors" and "it's a phone, but with memristors" and "it's an instant-on PC, but with memristors" and in all of those cases I would say that the patent should not be allowed, because those are "innovations" which are obvious to those skilled in the art.
Also, the software to store to memristors should not be patentable. "method by which data is semi-permanently stored in a memristor-based storage device" should not be patentable, because that skill (putting data in memory or storage) is obvious to every literate computer user, let alone software engineers.
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if you're that paranoid, it's fairly easy to have the OS wipe all user & program data from the memory at shutdown.
IMO that is no solution. A system can be easily reset/halted before an OS has a chance to neatly shut down.
Creating "Security RAM" modules would be more effective: Equipped with a capacitor for power, they could self-wipe at the hardware level when they detect a reset signal or power interruption. Given the precarious nature of info esp. on laptops, one would think this category of RAM would have already been developed.
The memristor is is just a way to model nonlinear circuit elements and is one of many components in a nonlinear expansion for circuit modeling. See this paper by Leon Chua, the memristor's inventor. Note that in this paper the fourth element of the four element torus is negative resistance and not the memristor. All of the publicity over the memristor has been (sucessfull) marketing by some researchers at HP. .
From the talk page for the memristor on wikipedia
"Resistance, Capacitance and Inductance are regarded as fundamental because to each there corresponds a different picture of what is going on with the energy. Resistance refers to the loss of energy to Joule heating. Capacitance refers to storage of energy in the electric field. Inductance refers to storage of energy in the magnetic field.
If memristance is the "fourth fundamental" circuit element then memristors must do something with the energy they are imparted other than turn it into heat, or store it in electric or magnetic fields. So what do memristor supporters have to say about this? nothing. This is not surprising, since the concept of memristance stems from a purely mathematical argument bent on taming the current/voltage relationships of nonlinear circuit elements. The concept of memristance was invented out of convenience to avoid dealing with frequency-dependent (time-dependent) resistance, inductance, and capacitance. Thus the memeristor is not "fundamental", unless in your book fundamental is synonymous with convenient."
How does this relate to a resistor which undergoes a discontinuous resistance change under critical conditions? Can you explain how it relates to the advertised device? Where is the charge being stored? Please continue to assume that I'm stupid, and explain the reasoning. My electromagnetic theory is thirty five years in the past now.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
Not really. It's on a microscopic scale, and at that level, a tiny current can vaporise silicon quite easily. That's how EPROMs work, and also why you need to be careful with static when handling circuits.
There are some who call me
No. I actually have no idea of what he's talking, because I have nearly no knowledge of electrical engineering. (I'm a software guy.)
I just recognized that you could combine those two equivalents that he wrote, and wanted to find out if I were right about EE at least once in life. ;)
Any sufficiently advanced intelligence is indistinguishable from stupidity.
The real news here is that we have a totally new circuit element and heaven only knows where that can take us.
Exactly how is this a fundamentally new circuit element? Most ohmic resistors change their resistance when a current is passed through them because the current causes heating and the heating changes their resistance. Since they take time to cool down they will have a (rather limited) memory too.
Yes this is a very interesting device and vastly more practical in terms of applications for memory but, unless it does something the articles do not mention, calling it a new fundamental circuit component seems wrong because it appears that you can mimic its behaviour using a well insulated piece of wire. Of course the wire is not very useful in terms of applications (outside electric heaters and light bulbs) but nevertheless it is a resistance whose value depends on previous current history.
It looks to me as though there is a confusion. The original vanadium oxide film when nonconducting can store supplied charge in a magnetic field. But the switching behaviour doesn't seem to be anything to do with this, unless there is some explanation not given in the article.
I guess someone from man.ac.uk ought to be interested in electronic storage, seeing as how you started off using cathode ray tubes:-)
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
I don't think this 'memristor' is suitable, at least in its current incarnation, to create Solid-State hard drives. Why not? It only retains your info for several hours. So, that essentially limits it to use as RAM. But RAM shouldn't store data for several hours.
The distinction here is that, on the hard drive, the data is always encrypted, but in RAM, it must be decrypted. I don't mind the hard drive storing the *encrypted* data for years, but I don't want my memory storing decrypted data for hours after I shut off my computer.
Now, that said, I could see, possibly, one application for this technology - used as a very large, very high-speed 'cache' in an otherwise conventional hard drive. That is, instead of the computer transferring data directly to/from the HD platters, it would read the data and write changes to the cache, then the hard drive would synchronize any changes in the cache back to the platters. Would, no doubt, speed up games and databases tremendously having a 100 GB high-speed cache. The key here is, if you have encrypted data, it is always encrypted in this cache (since the cache is just part of the hard drive), while your RAM is of a more 'conventional' nature that loses its state a few seconds or minutes after shutdown. Heck, with this tech, if your computer loses power, if the power comes back on within an hour or two, the hard drive could finish writing changes from the semi-persistent cache to the disk before bootup, so you minimize data loss.
Thanks for citing the ieee paper http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?arnumber=1083337. Unfortunately I am not a current member. Can the entire paper be found anywhere else online? Thanks this is a very interesting discussion.