Professor Invents Cheaper and Greener Way of Turning Sand into Silicon

A new method for turning silicon dioxide into crystalline silicon has been found

By Sebastian Pop on January 26th, 2013 10:55 GMT

The current means of creating crystalline silicon, an essential element in computer chips, is expensive and quite hard on the environment. Stephen Maldonado though, a professor of chemistry and applied physics at the University of Michigan (UM), has come up with an alternative.

Sand covers much of the Earth's surface, and makes up about 40% of the planet's entire crust, whether as part of beaches, the seabed, or sedimentary rocks.

What people might not know is that the silicon in every electronic chip is made out of sand. Sand is, after all, the common name for silicon dioxide.

The method for crystallizing the silicon into the state needed for technological use is done in rather extreme conditions though.

"The crystalline silicon in modern electronics is currently made through a series of energy-intensive chemical reactions with temperatures in excess of 2000° Fahrenheit (1093.3°C) that produces a lot of carbon dioxide," said Stephen Maldonado, professor of chemistry and applied physics at UM.

Maldonado recently managed to discover a better way, with the help of Junsi Gu and Eli Fahrenkrug, two chemistry graduate students.

The idea actually came from how rock candy is made. When water is saturated with sugar and boiled, the sugar can spontaneously form crystals.

Professor Maldonado found that using silicon instead of sugar and liquid metal instead of water allows for the crystalline silicon to be made at just 180°F (82.2°C), the temperature turkey is cooked at.

For those that want specifics, Maldonado and his colleagues made a solution of silicon tetrachloride and layered it over a liquid gallium electrode.

The electrons from the metal converted the silicon tetrachloride into raw silicon, which dissolved into the liquid metal as the process went on.

"The liquid metal is the key aspect of our process. Many solid metals can also deliver electrons that transform silicon tetrachloride into disordered silicon, but only metals like gallium can additionally serve as liquids for silicon crystallization without additional heat," the professor elaborated.

The potential applications in solar energy and semiconductors (CPUs, APUs, interface chips, etc.) are huge. There is no estimate for exactly how much cheaper and greener the making of crystalline silicon can become, but the difference should be more than visible.
Silicon manufacturing process
   Silicon manufacturing process
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