Tuesday, July 22, 2008

And Then There Was Light...Emitting Diodes

They've been around since the 1960s (mostly in traffic signals), but Light Emitting Diodes(LEDs) are lighting up the future.

I could rave about all the neat characteristics these luminous materials have, but only two are really important: LED lights only need to be replaced every 15 years, and they could potentially reduce the amount of electricity we consume by 10 percent, if used widely.

What more could one want in a lighting source? Unfortunately, there is a "dark" side to LEDs. They are painstakingly expensive. That's because a layer of sapphire is currently used in manufacturing LEDs.

While the idea of lighting your living room with dazzling gems might be attractive, it certainly isn't conducive to mass production. Researchers at Purdue University in Indiana have solved that problem, by developing a method to create LEDs on a thin disks of silicon coated in metal, making production a lot cheaper.

Gallium nitride is what causes light to be emitted in LEDs. While some of the light is projected up, some of it goes down and is lost. This accounts for part of the reason current LEDs are so costly- they require an additional reflector to bounce light back that would otherwise be lost.

The Purdue team managed to engineer an LED on a silicon layer, with a built-in metallic reflective layer, made of zirconium nitride. With these ingredients sprinkled onto the silicon, the disk is heated at extremely hot temperatures, causing a crystal structure to form that is key to functioning LEDs.

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