I’ve mentioned Graphene a few times in the blog and I wanted to spend some time explaining what sort of things people are doing with it, why it’s worthy of a Nobel Prize, and why it’s just plain cool! In fact, check out this picture:
Read more below for additional reasons why graphene is awesome…
What is Graphene?
When people think of molecules and crystals, they typically picture structures that extend in all three dimensions. Graphene however is actually more like a sheet of paper, in that it only has two dimensions. You can picture graphene as a sheet of carbon atoms, arranged in a honeycomb like pattern, where each sheet is only one atom thick (see image)
The amazing thing is that this material has been around forever, we just didn’t know it! The Nobel Prize winners isolated singular graphene sheets from graphite – the common material found in pencil lead. They also did it by using Scotch tape to pull off a single layer of graphene from the graphite. Despite the fact that graphene makes up graphite, the two materials could not be more different. Here is the promise of graphene, from Andre Giem, one of the Nobel Prize winners:
These are turning out to be wonder materials. Take graphene, the single layers of carbon atoms arranged in a honeycomb lattice that my colleagues and I first isolated in 2004. Graphene is stronger and stiffer than diamond, yet can be stretched by a quarter of its length, like rubber. Its surface area is the largest known for its weight. Despite graphene’s thinness it is impermeable to gases or liquids. It conducts heat and electricity better than copper, and can be made into transistors which are faster than those made from silicon.
Whereas graphite… well again it’s pencil lead. Not really that exciting. This just goes to show you how similar materials can have wildly differing properties when examined on the small nano scale versus the large bulk scale.
Uses as a Transparent Conductor
Graphene is interesting in that it can conduct electricity and heat amazingly well, something that is typically thought to reside in the realm of metals. This is great because unlike metals, graphene is transparent. Why is this useful? Well, imagine a solar cell. It needs to have an electrical contact on the front and on the back. But it also needs light to get through so one can’t just cover both sides with metal. Typically they only cover small parts with metal, but this reduces efficiency. The other option is to use a transparent conductor, such as Indium Tin Oxide (ITO). A recent study in Nature showed that graphene can be used in place of ITO as it transmits more light and isn’t as brittle. In addition they found out how to manufacture graphene into usable sheets (not as easy as it seems – see the size of the first flakes found as seen in the first image above). If it can be processed like this than it can be used in in large scale solar cells, and even in things like large touch screens and other thin electronic screens.
It’s not just electricity that it is good at conducting either – it has been shown that single sheets of graphene are better and conducting heat than thin layers of copper! This will be extremely useful in dissipating heat away from small electronic or even nano-mechanical devices.
Researchers at IBM have used graphene to fabricate transistors, the basic logic components that make up computer processors, that are faster and smaller than traditional transistors that are typically fabricated from silicon. Originally researchers were attempting to create graphene transistors by hand, still attempting to flake pieces of graphene off of graphite, and then assemble the transistors mechanically. These transistors worked but at a speed much slower than the silicon transistors. The IBM researchers used their expertise in making transistors to grow the graphene sheets in place. This improvement led to the graphene transistors that operate at 100 gigahertz (100 billion times per second), which is about 10 times faster than silicon transistors of the same size. With the potential to make transistors smaller than silicon transistors, the future of tiny computing devices looks bright. Read more here.
This is just a sampling of some of the neat things that graphene can do. Part of the reason that graphene research was awarded the Nobel prize was the literal explosion of research into it’s potential applications from, energy storage in ultracapacitors, to anti-bacterial applications, and even it’s ability to perform experiments into the strange effects of relativity once though to be solely in the realm of particle accelerators! Have any questions? Put them in the comments!
Original Graphene Paper: Novoselov, K. (2004). Electric Field Effect in Atomically Thin Carbon Films Science, 306 (5696), 666-669 DOI: 10.1126/science.1102896
New Processing Techniques: Bae, S., Kim, H., Lee, Y., Xu, X., Park, J., Zheng, Y., Balakrishnan, J., Lei, T., Ri Kim, H., Song, Y., Kim, Y., Kim, K., Özyilmaz, B., Ahn, J., Hong, B., & Iijima, S. (2010). Roll-to-roll production of 30-inch graphene films for transparent electrodes Nature Nanotechnology, 5 (8), 574-578 DOI: 10.1038/nnano.2010.132
Conduction Properites of Graphene: Seol, J., Jo, I., Moore, A., Lindsay, L., Aitken, Z., Pettes, M., Li, X., Yao, Z., Huang, R., Broido, D., Mingo, N., Ruoff, R., & Shi, L. (2010). Two-Dimensional Phonon Transport in Supported Graphene Science, 328 (5975), 213-216 DOI: 10.1126/science.1184014
Fast Graphene Transistors: Lin, Y., Dimitrakopoulos, C., Jenkins, K., Farmer, D., Chiu, H., Grill, A., & Avouris, P. (2010). 100-GHz Transistors from Wafer-Scale Epitaxial Graphene Science, 327 (5966), 662-662 DOI: 10.1126/science.1184289