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Graphene

What is Graphene?

Graphene is basically a single layer of graphite, a hexagonal array of carbon atoms extending over two dimensions endlessly; a two-dimensional honeycomb arrangement of carbon (sp2) atoms which is analogous to the layered structure of graphite.

Why Graphene?

Silicon has been the material of choice for electronic devices since the 1960s. However, within the next 10 years, fundamental property limitations of silicon will inhibit the ability to fabricate operational devices and circuits due to continuing device size reduction. The ability to reduce device size and thus pack more and more devices on a chip has allowed adherence to Moore’s Law and therefore has facilitated the phenomenal progression of the silicon-based semiconductor industry.

Epitaxial graphene (EG) has extraordinary electronic properties that offer the possibility of greatly enhanced speed and performance relative to silicon; this material may serve as the successor to silicon in integrated circuits and microelectronic devices.

How is Graphene Grown?

The GT MRSEC focuses on the growth of EG (single and multiple layers) on single crystal silicon carbide substrates. This approach offers the advantage that high quality layers can be grown on large area substrates. In addition, processes similar to those employed for silicon-based device manufacture can be used for the fabrication of graphene devices and circuits. In contrast, much of the world-wide effort has concentrated on exfoliated graphene, where graphene flakes are obtained by peeling layers from graphite. Although devices can be constructed on such sheets, the ability to fabricate large area arrays of high quality devices and hence establish consistency with the well-established silicon-based technology is severely restricted using exfoliated graphene techniques.

What is the history of graphene work at GT?

The excitement actually started more than a decade ago, when people studied carbon nanotubes and saw that they had really great electronic properties. A whole community evolved out of that, looking specifically at the properties of carbon nanotubes. From that evolved the idea that maybe carbon nanotubes were only a specific form of graphene and that two-dimensional graphene might also be a useful electronic material. In 2001, Professor de Heer thought that perhaps two-dimensional graphene, the basis of carbon nanotubes, could be used as an electronic material, and that’s how the graphene work project began.

Originally, while he was performing calculations on carbon nanotubes, he began to look at what would happen if there was no graphene tube, but instead, a graphene ribbon. He found that many of the properties that carbon nanotubes have, on paper at least, were also there in graphene ribbons. It was a theoretical calculation yet a very simple one. Later he realized that he was not the first one to make this calculation, but discovered that if a two-dimensional graphene sheet was grown and then cut into shapes, it could be a new electronic material.