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Thursday, July 3, 2014

New material could replace silicons in next-generation transistors

FIONA MACDONALD  
Scientists have demonstrated that a graphene-like material could help make near-perfect transistors that don't lose heat.
molyb6-27.jpg
Image: Kathryn McGill/Cornell University
As the transistors that make up electronics continue to shrink, there's increasing pressure to make them more efficient. And new research from Cornell University in the US suggests that a graphene-like material might just be the key to doing that.
The material is molybdenum disulfide and is an atom-thick semiconducting crystal. The two dimensional material is made up of atoms of molybdenum (grey in the image above) and sulfur (yellow).
Scientists first became interested in using it after studies showed that graphene would be the perfect material to make transistors with - except it doesn't allow for easy switching on and off of current, which is the key job of transistors.
Molybdenum disulfide, in contrast, has the necessary "band gap" to make it a semiconductor. 
But even more interestingly, researchers have discovered that it possesses another potentially useful property - in addition to charge and spin, the material has an extra degree of freedom called a valley. As the press release explains, this valley can produce a perpendicular chargeless current that doesn't lose any energy as it flows.
This sideways current is shown in the image above, triggered by a laser.
Effectively this means that the valley could be used to form a new-perfect, atom-thick transistor that would allow the creation of electronics that's don't dissipate heat, lead researcher Kin Fai Mak explained. That means they would be far more efficient than current electronics, which lose energy in the form of heat.
Now Mak and his team have now shown evidence of this valley-produced current in a functional transistor, using a laser of circularly polarised light. This light excited the electrons into the unusual sideways curve, a result that paves the way for further research on harnessing the potential of this current.
Their research is published in Science.
As the press release explains: These experiments bolstered the concept of using the valley degree of freedom as an information carrier for next-generation electronics or optoelectronics.
Watch this space…electronics could soon become a whole lot more efficient.