Nanotubes beam out bright light

Physicsweb Org ^ | 18 November 2005 | Liz Kalaugher

[PeaceBeWithYou]

Physicists in the US have generated extra-bright beams of infrared light from single-walled carbon nanotubes. The new technique is more efficient than many existing methods for producing light and could have applications in optoelectronics (Science 310 1171).

Phaedon Avouris of IBM Research, Jie Liu of Duke University and co-workers began by laying down nanotubes with diameters of 2-3 nanometres by chemical vapour deposition. The nanotubes spanned trenches in a silica coating on a silicon substrate. Palladium source and drain electrodes were then added to the nanotubes.

Suspended nanotubes

The IBM-Duke team found that when certain voltages were applied, the nanotubes emitted infrared light at the junction between the suspended and supported parts of the tubes. The emission was localized in a nano-sized area, which resulted in a very bright source of light: a 3 milliamp current was able to produce about 10⁵ times more photon flux than a large area LED.

The scientists believe the location of the emission is due to bending of the conduction and valence bands at the interface between the suspended and supported regions. This accelerates charge carriers (electrons or holes), which then create bound electron-hole pairs (called excitons) that recombine to emit light. According to the team, this excitation mechanism is about 1000 times more efficient than the conventional recombination of independently injected electrons and holes.

Avouris says that the nanotubes emit light with a wavelength of 1-2 microns, which covers the wavelengths employed in optical communications. Moreover, it is possible to tune the emission wavelength, producing either infrared or visible light, by using nanotubes with different diameters.

About the author

Liz Kalaugher is editor of nanotechweb.org

[PeaceBeWithYou]

Big breakthru.

[AntiGuv]

I don't have much clue what this is all about, but it sounds important! :)

FutureTechPing!

An emergent technologies list covering biomedical research, fusion power, nanotech, AI robotics, and other related fields. FReepmail to join or drop.

[samtheman]

Coming to a pair of glasses near you: a wide-screen TV that only you can see.

[King Prout]

you had something on this a few weeks back - mostly discussing use in producing VISIBLE light, but same stuff, same corporation IIRC

[SC Swamp Fox]

How about a low power, bright, flat-screen TV or monitor with several million pixels that you unroll and hang on a wall like a big poster.

[Army Air Corps]

"Coming to a pair of glasses near you: a wide-screen TV that only you can see."

Instead of glasses, you could watch TV on a contact lens or on the lens of your own eye via an implant.

[lmsii]

Although I am an attorney, I think what IBM is doing is laying the groundwork to replace standard computer chips with ones that work via light waves. Think of it as as a fiber optic computer chip.

[TaMoDee]

OK, I'm thinking about it. What's next?

[strategofr]

"According to the team, this excitation mechanism is about 1000 times more efficient than the conventional recombination of independently injected electrons and holes."

I hate to be overly cynical, but to me, this ranks with the many articles I read about how IBM technicians have made one transistor using X Principle, and it works 1000 times better than silicon, and a chip full of these trnsistors would be 10,000 times better than a Pentium and use 1/10th the energy. Then you never hear about it again.

I'm more dilletante than heavyweight in the technical area, but I have come to believe that there is a larger thanh exepcted inherent gap between these kind of "theoretical breakthroughs" and practical applications.

I think about the CRT (cathode ray tube---TV tube) and the internal combustion engine. LCDs have been around for decades and for decades they seemed like an obviously better idea than hot, high voltage CRTs. But for decades, the CRT dominated. Finally, the LCD is winning, but I'm amazed how long it took for this "logical" progression to occur.

The internal combustion engine (based on explosions---does that sound efficient?) has had similar longevity past what many expected.

[grey_whiskers]

Ping!

[knews_hound]

Check this out.

Cheers,

knews hound

http://knewshound.blogspot.com/

[bitt]

hey, glad your blog is back up...great article on our military

how's the arm?

[Irish_Thatcherite]

The emission was localized in a nano-sized area, which resulted in a very bright source of light: a 3 milliamp current was able to produce about 105 times more photon flux than a large area LED.

The applications of this will prove interesting!!

A very, very high fidelity monitor for example!!! (Have you got an electron microscope, I want to look at a pixel....)

[NicknamedBob]

"Think of it as as a fiber optic computer chip."

"OK, I'm thinking about it. What's next?"

Ah, next...

*** Excerpt from Book Three, "Action!" ***

Ruby continued. ‘If I can develop a different kind of processor, I may be able to do this type of project in just one or two hours.’

“What kind of processor would you need, Ruby? You already have the fastest processors we could find.”

‘Speed is not the problem, Sully. For image processing, we need parallel power. You are familiar with the history of computer microprocessors. They kept increasing the number of computation paths in the CPU, usually doubling them every few years.’

“Yes, Ruby. I know about that.”

‘Have you heard of optical processing? The CPU in an optical processor is theoretically capable of almost infinite parallel computations. Essentially, each computation is following a different optical path, and photons take the place of electrons.’

“Isn’t such research experimental?”

‘Some crude devices have been built. I believe I could modify one of my “chip furnaces” to produce a photonic microprocessor.’

“How long would that take, Ruby?”

‘I should be able to start your project in ten days, Sully, if I start now.’

“By all means, start now. At least it will cut about a week off the project.”

‘Yes, and I assume that you will have other projects in the future. The new chip will save time on them as well.’

“Excellent, Ruby. Do whatever you must to increase your capacity to what is needed.”

‘Thank you, Sully.’

“Thank you, Ruby!”

‘You are welcome, Sullivan Conrad.’

Sully rubbed his hands together. This was great! He should have realized that film images, digital images, and holographic memory storage would require an optical processing system. After all, it was optical to begin with!

Ruby began her preparations immediately. She mused internally; the chip described for this project would require something on the order of a one hundred by one hundred by one hundred three dimensional array of input channels. One million parallel computations per nanosecond.

Then after this chip was produced, she could start looking into designing a chip with proper capacity. Perhaps a one hundred thousand by one hundred thousand by one hundred thousand three dimensional array of input channels. A few quadrillion parallel computations per nanosecond. Yes, that sounded right.

The other advantage of optical computing was that it did not produce a lot of heat. To have that many transistors in such a small space would cause them to melt down immediately, if they could be built to start with. But light waves could pass in, around, and through each other without interference, and without noticeable heat buildup. All she would have to do then is provide the discrete light sources and storage mechanisms, and build an interface to the unit.

It would be considerably bigger than the first chip, but still very small in relation to the cabinets full of drawers of servers and microprocessors that had gone into her construction. How small? Let’s see, a sphere about twelve to fifteen centimeters in diameter should be easy to deal with.

*** End Excerpt ***

It's convenient to have a computer you can talk to, and which can build your projects for you, isn't it?

Be careful what you wish for!

[Irish_Thatcherite]

That optical processor is more imaginative than my theory about a screen comprising of nano-pixels!!

Ruby began her preparations immediately. She mused internally; the chip described for this project would require something on the order of a one hundred by one hundred by one hundred three dimensional array of input channels. One million parallel computations per nanosecond.

We are in the peta Hertz range here!!

Then after this chip was produced, she could start looking into designing a chip with proper capacity. Perhaps a one hundred thousand by one hundred thousand by one hundred thousand three dimensional array of input channels. A few quadrillion parallel computations per nanosecond. Yes, that sounded right.

They haven't even a prefix that high!! X-Hertz? Mega-exa Hertz?

[Wiz]

Let me in the FutureTech Ping. I just love these stories!

[NicknamedBob]

I wanted the implication to be that it was at least the equivalent of the human brain.

I like the character that developed from this in my story. I am currently involving her in a difficult situation. She may have to violate Asimov's rules.

Some would assume this leads to chaos -- I'm thinking ... growth.

[Irish_Thatcherite]

That's your work? Excellent!! Today's Wells or Verne!!

The Borg are in violation of Assimov's Rules, or is it a technicality because they are cyborgs?

[NicknamedBob]

"The Borg are in violation of Assimov's Rules"

The Borg are the latest in Mary Shelley's closet of scary monsters, which started with Frankenstein.

Jack Williamson's "The Humanoids" had their own kind of dread, similar to the Borg.

I pursue a future in which man and machine form a cooperative union, each doing what is best for it. Man extrapolates, machines interpolate.

Asimov's rules work in a literary discussion, but how do you go about programming them? I think the key distinction is self-awareness, and creativity. When machines can do or simulate these things, they will be our equivalents.

[Old Professer]

Are you sure that wasn't about a chemist and a grad student at Vanderbilt University in Nashville using nanocrystals suspended in a polyurethane substrate applied over LEDs that changed red light to white?