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."

Re:Melts like a chocolate bar

[Anonymous Coward]

correction:
it's actually 0.6 mA, so that would be 0.24W/byte, and only during the (very short) write pulse. Still some work to do, but it could possibly end up more efficient than flash memory.

Not vaporware...

[Menkhaf]

As the memristor was developed in HP Labs while working on fabrication techniques for "normal" memory, the fabrication technology is already here. It'll only be a short while before we'll see memristors in consumer products.

"HP prototyped a crossbar latch memory using the devices that can fit 100 gigabits in a square centimeter.[10] HP has reported that its version of the memristor is about one-tenth the speed of DRAM.[27]"

http://en.wikipedia.org/wiki/Memristor#Potential_applications [wikipedia.org]
[27] http://www.nytimes.com/2008/05/01/technology/01chip.html [nytimes.com]

Re:The flavour lasts forever.

[drinkypoo]

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.

Re:4th element?

[as400master]

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.

Practical relevance of this: Zero

[Bender_]

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.

Re:It is NOT a fourth basic component

[Hodapp]

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 [ieee.org])
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 [ieee.org]
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.

Re:fourth type?

[Stormy Dragon]

There are four basic quantities that are of concern in an electrical circuit: charge(q), current(i), voltage(v), and magnetic flux(phi). Those four quantities can be matched into pairs 6 different ways. Two of those pairs are time constrained by basic physical law: dq = i dt and dphi = v dt. Three of the remaining are determined by the properties of resistance(R), capacitance(C), and inductance(I): dv = R di, dq = C dv, and dphi = L di. Resistors, capacitors, and inductors are ultimately just devices that have a lot of one of those three properites and nearly none of the others.

It was speculated in the early 70's that there must be a fourth property, called memristance(M), that describes the 'missing' relationship: dphi = M dq. The memristor, then, is the corresponding device that has a lot of memristance but none of the other three properties. While memristance has been previously measured in complex systems, no one figured out how to build an feasible isolated memristor until just recently.

The four are considered fundamental in that none of the four can be built from a combination of the other three (e.g. you can't make a resistor from some combination of capacitors, inductors, and memristors) but any device can be built from some combination of the four (e.g. you CAN make a diode from L's, C', R's, and M's).

Re:The Memristor is NOT Fundamental

[Anonymous Coward]

You sir are a troll.

Nobody is talking about resistance capacitance and inductance when talking about fundamental passive circuit elements.
There are four and only four passive circuit elements because they are defined in that paper as being the result of a relation between two of the four Fundamental Circuit Variables that are Voltage, Flow, Charge and Flux. So you can combine them in only 4 possible ways: The Resistor, The Capacitor, The Inductor and The Memristor(charge and flux).

So stop pretending thats all an HP Conspiracy.