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Few things attract our attention like a sudden burst of light at night.
In Oak Ridge, researchers have the capability not only to produce but also control intense lighting in the lab coming from the world's most powerful plasma arc-based lamp. For eight years Craig Blue has been demonstrating the potential industrial applications of rapid radiant heating using flashes of infrared light from tungsten-halogen lamps and then shorter flashes of light from a high-power plasma arc-based lamp. Vortek Industries of Canada manufactured the early arc-based lamps. Mattson Technologies, a California company, purchased Vortek in 2004. Blue manages industrial technologies and materials processing at Oak Ridge National Laboratory, which owns two high-power plasma arc-based lamps. Blue has advised Mattson on how the lamp can be used as a research tool. By adjusting lamp-processing parameters such as flash time and power densities, Ron Ott can reach several extremes in a pursuit to achieve advances in flexible electronics. "We can flash the lamp down to 1 millisecond while discharging 12 megawatts, providing to the surface 20,000 watts per square centimeter and heating the surface on the order of 1 million degrees per second. Only nature can exceed these extremes." Ott leads a group that explores the potential of the high-power lamp's photons in helping to fabricate more-efficient, lower-cost thin-film batteries, thin-film transistors and photovoltaic cells for converting the energy of sunlight into electricity. "Our focus is to do high-temperature processing of non-crystalline silicon over broad areas on low-temperature substrates," Ott says. "Non-crystalline silicon and silicon-germanium layers are cheaper than crystalline silicon layers. "We have shown that we can initiate solid-phase crystallization, which will introduce a nanocrystalline structure with fewer defects and higher efficiencies. The goal is to optimize the microstructures to improve photon collection efficiencies for solar cells while not altering the underlying substrate." Furthermore, the lamp's flash of light will heat only the surface layers to extremely high temperatures. The substrate will barely be heated at all. That means the underlying layer, which is usually metal to withstand high-temperature processing, can be replaced with a cheaper plastic substrate capable of bending and conforming to a desired shape, giving rise to the term "flexible electronics." In 2004 Blue, Queen City Forging in Cincinnati, Ohio, and others received an R&D 100 award for an optimized combination of radiant and convection heating for processing materials. The forging company now uses this technology to make lightweight aluminum forged components to replace more expensive and heavier titanium and other metal parts for aerospace and automotive applications. In February 2008, producers and cameramen with the cable television program "Modern Marvels" came to ORNL to film the high-power plasma arc-based lamp for a feature on ultrahigh-temperature heating that will likely grab viewers' attention.—Carolyn Krause
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