February 3, 2010 weblog
Carbon Based Chips May One Day Replace Silicon Transistors
![Carbon Based Chips May One Day Replace Silicon Transistors](https://scx1.b-cdn.net/csz/news/800a/carbonbasedc.jpg)
(PhysOrg.com) -- IBM researchers are hopeful that, over the next decade, silicon-based transistors will be replaced by carbon-based transistors. IBM has already laid out the ground work for carbon-based transistors.
Graphene, one of the thinnest known materials, consists of a planar single sheet of carbon arranged in a honeycombed lattice. Graphene sheets also have higher carrier mobilities (the speed at which electrons travel at a given voltage) which translate to carrier mobilities that are hundreds of times larger than silicon chips used today. This makes graphene ideal for faster chip speeds.
![Image depicts carbon-based semiconductor chips with its dual-gate bi-layer graphene field-effect transistors. Carbon Based Chips May One Day Replace Silicon Transistors](https://scx1.b-cdn.net/csz/news/800a/1-carbonbasedc.jpg)
However there are a few problems that need to be overcome before carbon-based transistors can be useful. Single layers of graphene sheets act more like a conductor than a semiconductor due to fact they have no band gap.
Semiconductors have a band gap between their conductive and insulating state, which allows them to be easily turned on and off. With a missing band gap, graphene FETs (field-effect transistors) have terrible on-to-off current ratios which is hundreds of times smaller than silicon.
Graphene also heats up considerably when operated at saturated currents. This becomes a big concern because high-performance graphene devices preferably need to operate at the saturation current limits.
![Heat transfer from biased graphene into an underlying substrate can be much higher than that found in conventional silicon transistors. Carbon Based Chips May One Day Replace Silicon Transistors](https://scx1.b-cdn.net/csz/news/800a/2-carbonbasedc.jpg)
The IBM research team has obtained heat flow results by determining the temperature distribution in active graphene transistors using optical microscopy combined with electrical transport measurements. They also used heat-flow modeling to calculate how heat travels along and across a graphene flake.
The research has shown that substrate interactions become much more important in graphene electronics than in traditional MOSFETs and heterostructures. This leaves engineers to focus on non-polar substrates and substrates that do not trap charges.
More information: Additional information: arxiv.org/PS_cache/arxiv/pdf/0910/0910.3614v2.pdf
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