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Filling the Vacuum
Field emission displays exemplify the next step Samsung seeks to take in its corporate transformation from a high-tech competitor to an industry leader. “Display technology is hugely complex to begin with,” says Kim Jong Min, vice president and director of the materials lab at the institute. “And using nanotubes adds to that enormously, both because of the unavoidable problems that always come from exploring an unfamiliar area and the fact that here there is no model to follow.” According to Kim, nanotube-based field emission displays are so complex that no single firm can develop them by itself. In consequence, researchers around the world are splitting the technology into its components and informally assigning different groups to work on each one. Samsung, for instance, does not plan to make its own nanotubes, except for research purposes. Instead, it will buy them in powder form from Carbon Nanotechnologies, a Houston-based firm with a considerable arsenal of patents in the field. A gram of carbon nanotube powder, enough to make half a dozen 40-inch displays, cost $100 last year, Kim says, but will sell for less than $10 in two years. “That is a competition we won’t enter.”

Similarly, Samsung does not intend to focus on the glue that affixes the tiny tubes to their glassy base, itself a sticky technological challenge. The company is working with DuPont to come up with an adhesive that’s thin enough to spread, strong enough to hold the ultrathin tubes by their ends, resilient enough to retain its grip despite inevitable expansion and contraction from heat, and easy enough to remove that manufacturers can clean stray adhesive from the tops of the nanotubes, so they can spray out electrons.

Nor is the company trying to gain an advantage by developing the physical components of the display itself – the spacers that hold apart the top and bottom sheets of the screen, the high-vacuum packaging, the driver circuitry, and other standard field emission components and materials. Instead, it has joined a consortium of more than half a dozen European companies and universities created specifically to tackle those problems and incorporated the group’s early results into the 38-inch display now showing off Pierce Brosnan’s Bond-blue eyes.

Delegating these aspects of field emission display design still leaves plenty for Samsung to work on, beginning with the glass itself. The nanotubes have to shoot their electrons across a vacuum; otherwise they would be absorbed or deflected by air molecules. Yet making what amounts to a very wide, sheetlike vacuum chamber is difficult, because over a large area air pressure will tend to crush together the two sides of the screen. The obvious answer is to put a support pillar in the middle of the screen. But then, Saito explains, “you see the support in the middle of the picture.”

Equally problematic, in his view, is the thermal expansion and contraction of the display. When the nanotubes are emitting electrons, the display gets hotter, and all its materials expand; when the electron beam is off, they shrink. “The problem is how to accommodate the expansion,” Saito says. His team had to find materials whose thermal expansion coefficient was the same as that of glass, so that the entire display would expand and contract in concert.

Exactly how Samsung pulled all these pieces together is “our secret,” says Kim. “That’s what we do: we’re a company that makes devices.” But key to Samsung’s decision to focus on field emission displays, he admits, is the lucky fact that they can tolerate imprecision. With current technology, aligning the nanotubes across the back of the display is an inexact process. The tubes point in a jumble of different directions, and most are too broken or bent to emit electrons successfully. Fortunately, nanotubes are small: about 10,000 cover each pixel in the display. As a result, Kim says, “We expect that only 30 to 50 percent of them will work, but we only need 30 to 50 percent to light up the pixel and deceive the human eye.”

Samsung is pleased enough with the result to permit a journalist from Technology Review to be the first non-Korean reporter to visit the Advanced Institute of Technology. Walking through the institute’s maze of small fluorescent-lighted laboratories, each with its coterie of white-coated researchers and glowing computer screens, Kim says that the display consumes about 100 watts, about a third of the power required for an average plasma screen of comparable size. “That’s just for now,” he adds. A bare two millimeters thick, the glass of the screen is thin enough to make the display slimmer than anything now on the market.

Arriving at the display, Kim introduces it with the slight anxiety of a proud parent hoping that strangers will appreciate the special qualities of his offspring. The image is as sharp as those produced by traditional high-definition picture tubes with similar display sizes, though the screen has several small blank spots. (“Prototype difficulties,” Kim explains.) Asked whether the technology is almost ready for market, the scientists in the room look at each other uncertainly. Samsung, Kim finally says, has just begun to work on the real challenge in bringing nanotechnology to the world: making the product affordable. The economic problems, he says, “are much, much harder than the technological ones.”

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