Making computers from a pencil trace

Rensselaer researchers have discovered a new technique to exploit the extremely efficient conductive properties of graphene - a one-atom-thick sheet of carbon - making it a possible replacement for copper and silicon in nanoelectronics.

Working with graduate student Philip Shemella and others, Saroj Nayak, associate professor of physics, applied physics, and astronomy, has demonstrated for the first time that the length and width of graphene directly impacts the material's conduction properties.

In the form of a long 1-D nanoscale ribbon, which looks like molecular chicken wire, graphene demonstrates unique electrical properties that include either metallic or semiconducting behaviour.

When short segments of this ribbon are isolated into tiny zero-dimensional segments called ''nanorectangles,'' where the width is measured in atoms, they are classified as either ''armchair'' or ''zigzag'' graphene nanoribbons. Both types of nanorectangles have unique and fascinating properties.

The team used quantum mechanical simulations with predictive capability to carry out their work. Their computational study showed for the first time that the length of graphene may be used to manipulate and tune the material's energy gap. This is important because energy gaps determine if the graphene is metallic or semiconducting.

Generally, when graphene is synthesised, there is a mix of metallic and semiconductor materials. But Nayak's findings give researchers a blueprint that should allow them to purposefully make entire batches of either one or the other.

This research is an important first step for developing a way to mass-produce metallic graphene that could one day replace copper as the primary interconnect material on nearly all computer chips, the researchers say.