Ferroelectrics could pave way for ultra-low power computing

Sep 12, 2011
Shown is a rendition of an experimental stack made with a layer of lead zirconate titanate, a ferroelectric material. UC Berkeley researchers showed that this configuration could amplify the charge in the layer of strontium titanate for a given voltage, a phenomenon known as negative capacitance. Credit: Asif Khan, UC Berkeley

Engineers at the University of California, Berkeley, have shown that it is possible to reduce the minimum voltage necessary to store charge in a capacitor, an achievement that could reduce the power draw and heat generation of today's electronics.

"Just like a Formula One car, the faster you run your computer, the hotter it gets. So the key to having a fast microprocessor is to make its building block, the transistor, more energy efficient," said Asif Khan, UC Berkeley graduate student in electrical engineering and computer sciences. "Unfortunately, a transistor's power supply voltage, analogous to a car's fuel, has been stuck at 1 volt for about 10 years due to the of its operation. Transistors have not become as 'fuel-efficient' as they need to be to keep up with the market's thirst for more computing speed, resulting in a cumulative and unsustainable increase in the power draw of . We think we can change that."

Khan, working in the lab of Sayeef Salahuddin, UC Berkeley assistant professor of and computer sciences, has been leading a project since 2008 to improve the efficiency of transistors.

The researchers took advantage of the exotic characteristics of ferroelectrics, a class of material that holds both positive and negative electrical charges. Ferroelectrics hold even when you don't apply a voltage to it. What's more, the in ferroelectrics can be reversed with the application of an external .

Getting more bang for the buck

The engineers demonstrated for the first time that in a made with a ferroelectric material paired with a dielectric – an electrical insulator – the charge accumulated for a given voltage can, in effect, be amplified, a phenomenon called negative capacitance.

The team report their results in the Sept. 12 issue of the journal Applied Physics Letters. The experiment sets the stage for a major upgrade to transistors, the on-off switch that generate the zeros and ones of a computer's binary language.

"This work is the proof-of-principle we have needed to pursue negative capacitance as a viable strategy to overcome the power draw of today's transistors," said Salahuddin, who first theorized the existence of negative capacitance in as a graduate student with engineering professor Supriyo Datta at Purdue University. "If we can use this to create low-power transistors without compromising performance and the speed at which they work, it could change the whole computing industry."

The researchers paired a ferroelectric material, lead zirconate titanate (PZT), with an insulating dielectric, strontium titanate (STO), to create a bilayer stack. They applied voltage to this PZT-STO structure, as well as to a layer of STO alone, and compared the amount of charge stored in both devices.

"There was an expected voltage drop to obtain a specific charge with the dielectric material," said Salahuddin. "But with the ferroelectric structure, we demonstrated a two-fold voltage enhancement in the charge for the same voltage, and that increase could potentially go significantly higher."

Computer clock speed hits a bottleneck

Since the first commercial microprocessors came onto the scene in the early 1970s, the number of transistors squeezed onto a computer chip has doubled every two years, a progression predicted by Intel co-founder Gordon Moore and popularly known as Moore's Law. Integrated circuits that once held thousands of transistors decades ago now boast billions of the components.

But the reduced size has not led to a proportional decrease in the overall power required to operate a computer chip. At room temperature, a minimum of 60 millivolts is required to increase by tenfold the amount of electrical current flowing through a transistor. Since the difference between a transistor's on and off states must be significant, it can take at least 1 volt to operate a transistor, the researchers said.

"We've hit a bottleneck," said Khan. "The clock speed of microprocessors has plateaued since 2005, and shrinking transistors further has become difficult."

The researchers noted that it becomes increasingly difficult to dissipate heat efficiently from smaller spaces, so reducing transistor size much more would come at the risk of frying the circuit board.

The solution proposed by Salahuddin and his team is to modify current so that they incorporate ferroelectric materials in their design, a change that could potentially generate a larger charge from a smaller voltage. This would allow engineers to make a transistor that dissipates less heat, and the shrinking of this key computer component could continue.

Notably, the material system the UC Berkeley researchers reported shows this effect at above 200 degrees Celsius, much hotter than the 85 degrees Celsius (185 degrees Fahrenheit) at which a current day microprocessor works.

The researchers are now exploring new ferroelectric materials for room temperature negative capacitance in addition to incorporating the materials into a new transistor.

Until then, Salahuddin noted that there are other potential applications for ferroelectrics in electronics. "This is a good system for dynamic random access memories, energy storage devices, super-capacitors that charge electric cars, and power capacitors for use in radio frequency communications," he said.

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User comments : 17

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SlashV
1 / 5 (4) Sep 12, 2011
"Just Like a Formula One Car" ?? No, not really. Car Analogy Fail.
Skultch
5 / 5 (6) Sep 12, 2011
"Just Like a Formula One Car" ?? No, not really. Car Analogy Fail.


No, not really a fail. It's an "analogy;" you aren't suppose to thing it's "just like" a car. The analogy is quite apt if you know anything about internal combustion engines, turbos, and inter-coolers.
wealthychef
5 / 5 (1) Sep 12, 2011
What's missing for me is what is in the way of getting this to market. How many years and what are the obstacles remaining? Is it cost effective? Etc.
Nanobanano
1.7 / 5 (7) Sep 12, 2011
What's missing for me is what is in the way of getting this to market. How many years and what are the obstacles remaining? Is it cost effective? Etc.


Don't be mislead.

The processor is one of the least power consuming components in a computer or hand-held device. That display or monitor and the speakers actually use more power.

The main people likely to benefit from this are large business, ISP, and IT companies; mainly anyone large enough to have server farms.

A few pennies per day less to run an individual PC, or a few minutes longer on a phone's charge isn't going to be revolutionary.

it's kind of like if your car got one extra mile per gallon, you probably wouldn't even notice it, particularly since the upgrade to the engine and the design of the car probably increased it's purchase price by more than the value of the energy savings in it's life time.
Royale
5 / 5 (9) Sep 12, 2011
I took it a different way Nanobanano.
It seems to me that they're not really talking about power savings as much as voltage cutbacks which can allow better heat dissipation... That would in turn lead to smaller transistors and faster processors. They'd be able to increse the Ghz much more quickly. (Hasn't anyone else noticed that they hit a wall years ago in Ghz and just started adding more cores? Even though the programming of parallel processing hasn't caught up yet.. I think this would be a significant achievement if they're able to realize this kind of technology (assuming equal reliability).
SemiNerd
5 / 5 (2) Sep 12, 2011
I disagree. Reducing the amount of energy required for a given speed usually means that I can get increased speed using the same amount of energy. This could potentially make it possible to make faster computers, not just power power ones.

A universal decrease in the power and voltage required to operate transistors would make everything using transistors lower power. That could have a very significant effect, because there are LOTS of applications where low power is important (all batter operated devices, space applications, etc).
CHollman82
3 / 5 (2) Sep 12, 2011
"Just Like a Formula One Car" ?? No, not really. Car Analogy Fail.


I don't know, I work as an electrical/software engineer (dual major) and I think it's actually a decent analogy.
CHollman82
1 / 5 (1) Sep 12, 2011
Don't be mislead.

The processor is one of the least power consuming components in a computer or hand-held device. That display or monitor and the speakers actually use more power.

The main people likely to benefit from this are large business, ISP, and IT companies; mainly anyone large enough to have server farms.


Don't be mislead.

Fans and other active cooling elements use more power than anything else in your computer. This technology will reduce power consumption of the electronic components, but it will also reduce heat generation, requiring less power hungry cooling techniques.
Husky
not rated yet Sep 12, 2011
it would be nice if the Ghz could be cranked up again, for most consumers a fst single or dual core is more meaningfull than having an underused 8 core meant for servers handling many user requests or VMs
CHollman82
1 / 5 (1) Sep 12, 2011
it would be nice if the Ghz could be cranked up again, for most consumers a fst single or dual core is more meaningfull than having an underused 8 core meant for servers handling many user requests or VMs


All 4 cores on my home PC are in use at all times. All windows NT family of operating systems (including XP/vista/7) take advantage of SMP as do many popular desktop PC applications.
Nanobanano
1 / 5 (1) Sep 12, 2011
Don't be mislead.

Fans and other active cooling elements use more power than anything else in your computer.


No they don't. Not even close.

The fans in my computer verifiably have the smallest power supply leads, and while the motherboard technically does have the largest power supply, that's an unfair comparison, since it's actually powering the video, sound card, Ram, processor, and all the other chips on board as well.

Then you have the hard drive which is spinning at thousands of RPM as well, which is very costly in energy.

THEN you have the monitor, which uses so much power it's actually on a seperate power supply cord, and in my case runs on a seperate outlet...

Yeah, processor is actually very small power consumption compared to the system as a whole, fans are the only thing smaller, actually.
Pete1983
not rated yet Sep 12, 2011
it would be nice if the Ghz could be cranked up again, for most consumers a fst single or dual core is more meaningfull than having an underused 8 core meant for servers handling many user requests or VMs


All 4 cores on my home PC are in use at all times. All windows NT family of operating systems (including XP/vista/7) take advantage of SMP as do many popular desktop PC applications.

Well XP didn't really take much advantage of SMP, and many applications do not do terribly well with it either. As much as multi-core is fun, for a desktop machine I always go with more Ghz over more cores. Generally a 4 core can be overclocked more than a 6 core system, and this generally gives you better desktop performance. More cores are really for servers.
niio
not rated yet Sep 13, 2011
Processors are major power consumers in servers, two thirds or more of the total. But this advance could be applied to all transistors, not just processors, so the savings might apply to 90% of the power used in servers. Since power used equals heat produced, you would save in cooling costs as well.
CHollman82
1 / 5 (1) Sep 13, 2011
The fans in my computer verifiably have the smallest power supply leads


The smallest leads? That matters how?

and while the motherboard technically does have the largest power supply, that's an unfair comparison...


Goes without saying, though I still don't know what you think the size of the power supply or the size of the electrical leads have to do with anything, you're speaking out of your ass. Newsflash, the fans are on the same PSU as the rest of it.

Then you have the hard drive which is spinning at thousands of RPM as well, which is very costly in energy.


Old spinning platter hard drives use a lot of power too, yes.

THEN you have the monitor, which uses so much power it's actually on a seperate power supply cord, and in my case runs on a seperate outlet...


The monitor is not part of the computer.

Yeah, processor is actually very small power consumption compared to the system as a whole, fans are the only thing smaller, actually.


nope.
CHollman82
1 / 5 (1) Sep 13, 2011
Nanobanano, consider the amount of Work done by these components and you'll realize why fans consume a lot of power. Fans actually push air, constantly. The hard drive accelerates a spinning mass... these things use a lot of power because they propel mass... unlike solid state electronics which mostly consume power by converting electricity to heat. In general, anything with moving parts is going to consume a lot of energy.
CHollman82
3 / 5 (2) Sep 13, 2011
120mm case fans consume up to 15w each, most gaming computers will have 3, servers have even more. We are talking 50 to 100 watts just to cool the processor, which uses about the same amount of power (80-120 or so)... if this new technology allows solid state electronics to produce less heat you can eliminate half of the energy required to use them, and that was the point.
gimpypoet
not rated yet Sep 18, 2011
Engineers at the University of California, Berkeley, have shown that it is possible to reduce the minimum voltage necessary to store charge in a capacitor, an achievement that could reduce the power draw and heat generation of today's electronics.
no one pointed out that this article started out to say capacitors would use less voltage, then changed to say transistors. a cap holding full charge gives off lots of heat,holding less voltage would equate to less heat, less heat = better performance. the voltage would transfer to the transitors better, reducing heat. heat dissipation bleeds off energy in a system, as waste heat. holding less voltage means less waste heat = better performance.

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