From semimetal to semiconductor

Progressively magnified images (left to right; scale bars: 400, 10, and 1 nm) of graphene nanoribbons grown on germanium semiconductor wafers. Credit: Michael Arnold/University of Wisconsin-Madison

The quest for graphene has been on for several years now. We have been able to develop small quantities of graphene, study its properties and understand that this material (a single layer of carbon atoms) can prove amazingly useful in many areas, from micro sensors detecting any kind of molecules and ambient parameters, filtering water, creating extremely resistant surfaces and materials with exceptional strength, highly conductive materials and electronic components.

The challenge is in manufacturing it in industrial quantity and with the precision required in its specific application field.

Europe has launched the Graphene Flagship Project and many European partners are working to deliver on the promises.

At the university of Wisconsin-Madison scientists have discovered how to manufacture tiny graphene ribbons less then 10nm wide and dispose them in a very precise geometric architecture such as to turn the natural semi-metallic properties of graphene into semi-conductor properties (like doped silicon). This allows the use of graphene as a transistor.  Previously scientists around the world have proved that graphene can have semiconductor characteristics by adding a doping atom to it but we have not found, so far, an industrial process for doing it.

On the contrary, the team at Wisconsin Madison has been able to grow the nano-ribbon of graphene onto a silicon substrate (very slowly, 5nm per hour...) with a technique that piggy back on existing industrial processes.... Hence the hope that this approach can lead to possible use in chip manufacturing.

The way is still long, since the silicon industry has had over 50 years to perfect manufacturing processes and finding something new that can yield the same effectiveness and deliver some more is really challenging and it is going to take a good part of the next decade, in my view.

Author - Roberto Saracco

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