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Non-Boolean logic used to tackle Graphene's lack of bandgap

Posted: 10 Sep 2013 ?? ?Print Version ?Bookmark and Share

Keywords:Graphene? bandgap? silicon era? Non-Boolean?

Graphene has been labelled as the miracle material that will extend the semiconductor roadmap past the silicon era. However, its lack of bandgap has crippled progress. Instead of modifying graphene to create a bandgap and lowering its high electron mobility, Researchers from the University of California in Riverside (UCR) have proposed the adoption of the non-Boolean logic that graphene naturally exhibits.

"Graphene devices, when biased as we propose, reveal negative differential resistanceNDRan effect that has its roots in graphene's symmetric band structure. These non-linear NDR current-voltage characteristics can be used in order to obtain bi-stable or bi-valued outputs. This means that for some input values you will get two output valuesunlike in conventional logic where you have single-valued outputsand these bi-valued regions can be used for constructing a non-Boolean logic in circuits with very high mobility and very high electron saturation velocity, which makes these circuits very fast. The main idea is to make use of the bi-stable outputs provided by each stage and to build a multi-valued logic unit," said UCR professor Alexander Baladin.

 non-Boolean logic

Figure 1: Scanning electron microscopy (SEM) image of novel graphene device implementing non-Boolean logic (with UCR logo etched in graphene at top). Scale bar is one micron.(Source: University of California at Riverside).

According to Balandin and his collaborators, UCR professors Roger Lake and Alexander Khitun, these super-fast non-Boolean logic circuits can be implemented with graphene field-effect transistors connected to harness NDR in circuits that are particularly well suited for many data-processing tasks, such as image recognition, data encryption, and database search.

"The observation of the NDR in the graphene double-gate transistors opens a new horizon for building special analogue logic circuits, which can solve some special problems more efficiently than the conventional digital processors," professor Khitun told us.

Guanxiong Liu, who built the graphene transistors in Balandin's lab, and Sonia Ahsan, who simulated the devices using atomic-scale models while working under Lake, both earned their doctorates at UCR while contributing to this research.

- R. Colin Johnson
??EE Times

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