Nanotubes are bidding for star billing on big screens

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Sept. 12, 2003 – Carbon nanotubes, once a darling of the display industry, are re-emerging as an attractive candidate for flat panel displays in big-screen televisions. DuPont announced Wednesday that it is licensing a carbon nanotube-based technology from the startup Nanomix  for field emission displays (FEDs), while Motorola Inc. recently unveiled a competing approach using nanotubes.

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They join the industrial giant Samsung and little-known startup cDream Corp. in efforts to enter the billion-dollar display market. Their technologies vary greatly, and the winner — if there is one — could bring opportunities to nanotube manufacturers and R&D companies. Whether nanotube-based FEDs offer enough advantages to replace existing displays or overshadow other emerging technologies remains to be seen, analysts say.

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 “The large screen display market is a crowded one right now,” said Kimberly Allen, director of technology and strategic research at iSuppli/Stanford Resources. Plasma and projection televisions dominate the market, but cost and quality issues leave them vulnerable.

“As they (nanotube-based FEDs) become more technically competent, they offer compelling qualities,” she said.

Samsung piqued industry’s interest in nanotube-based displays in the late 1990s when it demonstrated a carbon nanotube FED prototype. The nanotubes, which are likened to chicken wire wrapped into a tube shape, easily released electrons from their tips under low voltage, making them ideal field emitters. Ise Electronics, a subsidiary of Noritake Co. in Japan, followed up with a competing prototype.

But early techniques were rife with technical problems. Researchers incorporated nanotubes into a paste that was placed on a substrate. The haphazard placement of the tubes and their tendency to clump together created spotty illumination.
Motorola bypasses that problem by growing carbon nanotubes in a specific and orderly manner on substrates using a low-temperature chemical vapor deposition (CVD) process. The process relies on a proprietary catalyst that ensures the tubes have a small diameter and sharp tips, said Ken Dean, principal staff scientist at Motorola Labs.

More importantly, the technique allows Motorola to drive down the costs of FEDs on two fronts, Dean said. Since the CVD process is low temperature, it can be used on inexpensive silicon substrates. And Motorola can keep the devices’ voltage and current requirements in line with low-cost manufacturing by growing the tubes in precise sizes and densities.

Height, diameter and tip sharpness affect voltage, Dean said, while density affects current.

“It’s significantly easier to make nanotubes sharp” with their method, he said. If tubes are sharp, they emit more readily at a low voltage. Concerning current, “You really want them (tubes) about as far apart as tall. We grow a sparse enough set of nanotubes to get a high current for field emission.”

Today’s large high-definition plasma televisions can sell for $10,000 or more, in part because of manufacturing costs associated with the higher-voltage electronics in the displays. Projection televisions cost significantly less, but work best in dark settings.

“Plasma is expensive. We think it will remain expensive,” Dean said. “This is a race we think we’ll win. We have the cost advantage.”

Motorola is in the process of building a 6-inch demo and is looking for partners in Asia to make and distribute the FEDs. But Motorola is not alone.

California-based startup cDream unveiled another carbon nanotube-based FED in May at a Society for Information Display symposium in Baltimore, and was scheduled to attend other conferences in Asia this year. Like Motorola, it claims it can grow nanotubes using a low-temperature type of CVD process.

“They’re an interesting dark horse candidate,” said Allen, who added the small team sprang from the ranks of the former San Jose-based FED developer Candescent Technologies.

Nor have companies abandoned approaches using nanotubes mixed with other materials. Samsung and DuPont independently are pursuing thick film techniques for larger displays. DuPont is exploring several methods, and has licensed at least two technologies from nanotech startups to develop materials for flat panel displays.

DuPont Electronic Technologies is combining its expertise in thick film technology with California-based Nanomix to make and sell carbon-nanotube materials for FEDs. In 2002, DuPont Central Research and Development licensed a technique for making carbon nanotubes from Houston-based Carbon Nanotechnologies Inc. (CNI) for displays.

DuPont uses a thick film of nanotubes and inorganic powders that includes a photoactive component, said Lap-Tak Cheng, a senior research associate at DuPont and its team leader for field emission display materials. It then photoimages the material with a photomask to get fine features. It’s a technique the company believes will be scalable and cost effective, Cheng said.

“The thick film approach gained some promise because of progress in plasma,” Cheng said. “DuPont has a strong position in this area.”

Like Motorola, DuPont intends to pair up with a leading FED supplier. “We will not make displays,” Cheng said. “If we’re successful, we’ll have options. Working with a partner would be a likely scenario.”

The nanotube industry has a stake in this battle, too. Progress in both camps suggests FEDs may be among nanotubes’ first markets, nanotube manufacturers say. But the nanotube makers will benefit only if tubes are used in bulk and not grown directly on substrates.

“We do believe single-wall nanotubes, or some type of nanotube, will be in flat panel field emission displays in the next couple — two to three — years,” said Dan Colbert, vice president of major development strategies at CNI. “From the beginning it’s been one of our focus areas.”

CNI specializes in single-wall nanotubes, which work well at low voltages. They are one of several materials DuPont is evaluating, Cheng said.

Other potential beneficiaries include research and development companies such as Applied Nanotech Inc. (ANI) that focus on nanotube applications. Like DuPont and Motorola, ANI holds patents that may come into play if nanotube-based FEDs reach the marketplace.

“If its an electron emission mode, they must license our patents,” said Zvi Yaniv, ANI’s president and chief executive. ANI, a subsidiary of SI Diamond Technology Inc., demonstrated a 14-inch diagonal carbon nanotube display in April of 2002 and plans to unveil another demo display in 2004.

But the analyst Allen cautions that the display industry is an ever-changing field of attractive options. “The competing technologies are not a standing target,” she said.


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