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Nanoribbons Create On/Off Switch for Graphene

Nanoribbons Create on/off Switch for Graphene
July 3, 2017 | Source: Oak Ridge National Laboratory, ornl.gov, 30 March 2017, Dawn Levy

A new way to grow narrow ribbons of graphene, a lightweight and strong structure of single-atom-thick carbon atoms linked into hexagons, may address a shortcoming that has prevented the material from achieving its full potential in electronic applications. Graphene nanoribbons, mere billionths of a meter wide, exhibit different electronic properties than two-dimensional sheets of the material.

Confinement changes graphene’s behavior. Graphene in sheets is an excellent electrical conductor, but narrowing graphene can turn the material into a semiconductor if the ribbons are made with a specific edge shape.  In wide sheets, graphene doesn’t have an energy gap — an energy range in a solid where no electronic states can exist. That means you cannot turn it on or off.

Previous efforts to make graphene nanoribbons employed a metal substrate that hindered the ribbons’ useful electronic properties.

Now, scientists at ORNL and North Carolina State University report in the journal Nature Communications that they are the first to grow graphene nanoribbons without a metal substrate. Instead, they injected charge carriers that promote a chemical reaction that converts a polymer precursor into a graphene nanoribbon. At selected sites, this new technique can create interfaces between materials with different electronic properties. Such interfaces are the basis of semiconductor electronic devices from integrated circuits and transistors to light-emitting diodes and solar cells.