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Appeared on: Thursday, June 17, 2010
POSTECH Scientists Develop New Material For Faster Sillicon Chips

Scientists at S.Korea's Pohang University of Science and Technology (POSTECH) on Thursday said they have developed a new silicon material technology that can drastically improve performance of semiconductor devices used in mobile communication devices.

A team led by professor Yeom Han-woong have found a way to drastically decrease the effective mass of a silicon material widely used to make semiconductors. The effective mass of a silicon-based material directly affects the speed of electrons moving through it. Lower mass translates into quicker movement of electrons and speedier processing of data and information if the silicon material is made into a computer chip. The scientists say that they have managed to decrease the effective mass of the silicon material by more than one-twentieth using the metal atomic layer and silicon interface method.

A semiconductor made from such a silicon material can process data and information on par with the best mobility transistors used in all mobile communications devices, the scientists said.

The paper "Nearly Massless Electrons in the Silicon Interface with a Metal Film" has beehas been published in the latest Physical Review Letters journal. Here is the official abstract of the paper:

"We demonstrate the realization of nearly massless electrons in the most widely used device material, silicon, at the interface with a metal film. Using angle-resolved photoemission, we found that the surface band of a monolayer lead film drives a hole band of the Si inversion layer formed at the interface with the film to have a nearly linear dispersion with an effective mass about 20 times lighter than bulk Si and comparable to graphene. The reduction of mass can be accounted for by a repulsive interaction between neighboring bands of the metal film and Si substrate. Our result suggests a promising way to take advantage of massless carriers in silicon-based thin-film devices, which can also be applied to various other semiconductor devices."

Organic nanoelectronics a step closer

While South Korean researchers are trying to improve the performance of silicon chips, researchers at McGill Universtiy in Montreal have made some progress in the development of low-cost organic semiconductors that could rival silicon.

The researchers have reported a breakthrough that could help organic semiconductors bridge the considerable performance gap with silicon chips.

Although they could revolutionize a wide range of high-tech products such as computer displays or solar cells, organic materials do not have the same ordered chemical composition as inorganic materials, preventing scientists from using them to their full potential. But an international team of researchers led by McGill's Dr. Dmitrii Perepichka and the Institut national de la recherche scientifique's Dr. Federico Rosei have published research that shows how to solve this decades-old conundrum. The team has effectively discovered a way to order the molecules in the PEDOT, the single most industrially important conducting polymer.

Although Dr. Perepichka is quick to point out that the research is not directly applicable to products currently in the market, he gives the example of a possible use for the findings in computer chips. "It's a well known principle that the number of transistors in a computer chip doubles every two years," he said, "but we are now reaching the physical limit. By using molecular materials instead of silicon semiconductor, we could one day build transistors that are ten times smaller than what currently exists." The chips would in fact be only one molecule thick.

The team used an inorganic material - a crystal of copper - as a template. When molecules are dropped onto the crystal, the crystal provokes a chemical reaction and creates a conducting polymer. By using a scanning probe microscope that enabled them to see surfaces with atomic resolution, the researchers discovered that the polymers had imitated the order of the crystal surface. The team is currently only able to produce the reaction in one dimension, i.e. to make a string or line of molecules. The next step will be to add a second dimension in order to make continuous sheets ("organic graphite") or electronic circuits.

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