Arthur S. Davis National University 10/23/2013
The evolution of computers replacing mechanical and electrical relays with vacuum tubes, then transistors and eventually finely sculpted silicon wafers is about to see a new transformation. Using a material so common that it is part of almost everything we see, touch, eat or breathe, scientists and engineers are busy making products that will warp our vision of the future. Carbon is as old as the hills and in its newest form it could quickly eclipse previous advancements in computer processing and storage. Computer circuits will soon become smaller, faster and more resilient in extreme environments because they will be made from one of the strongest materials in the world.
Carbon comes in two forms that we can instantly recognize: graphite as in charcoal or coal and diamonds. Their chemical properties seem opposed to each other but they both possess qualities that make them uniquely strong and resilient. Diamonds are beautiful and romantic; aligned with the rich and famous, young lovers and long marriages. Conversely, graphite seems tenuous, slippery and filthy; good for burning as fuel or making pencils. However, if we look into the chemical properties of the two we can better understand why the flexible and self-aligning properties of graphite make it a best choice for many products today.
Diamonds find their strength and beauty through the way the individual carbon atoms are associated. Carbon atoms have four outer electrons. In a diamond each outer electron of a carbon atom is shared with other neighboring atoms. Because no electrons are left over for conduction, diamonds are a good insulator and they are transparent because light cannot easily excite and be absorbed by the well bonded electrons. The atomic structure of a diamond gives it the hardness to be cut and polished into beautiful shapes for jewelry and extreme sharpness for cutting tools.
On first inspection, graphite exhibits the qualities of a very soft material. Anyone handling charcoal or coal will find it rubbing off and spreading to everything it touches. This "softness" is caused by the way carbon atoms are composed in graphite. Only three of the outer electrons form bonds with other carbon atoms. The three-way bond forms a sheet of interlocked hexagonal structures leaving one electron of each atom to form a weaker bond to other sheets of carbon atoms. The weak bond between sheets creates the quality that allows graphite to be transferred easily to another surface. This can be demonstrated when writing with a number two pencil. However, the bonds within the sheet are much stronger. Only one atom thick, a sheet of linked carbon atoms could be made into a hammock that would swing a small cat ( Neto & Geim, 2012).
In 2004, Andre Geim and Konstantin Novosolev of the University of Manchester leveraged the transferable quality of graphite by using adhesive tape to isolate a one-atom thick layer of graphite (Wright, 2013). Dubbed graphene, the material has attracted the interest of many scientists and electronics engineers, including the IBM company which produced the first integrated circuit using graphene based transistors (Savage, 2011). In addition to the amazing physical qualities, graphene's perfect honeycomb structure promotes extreme electrical conductivity. Electrons can move about with almost no resistance; up to 500 times faster than silicon used in current computer circuits (Wright, 2013). IBM's team used this superconductive property to double the speed of comparable sized silicon components and they predict much greater improvements. Additionally, the material qualities of graphene could enable it to be stitched into clothing as a cellphone or GPS receiver. Considering these few examples, the possibilities for new applications are great.
Currently, the production of graphene and graphene based electronics is expensive. At 3,000 dollars per square meter, the price can be discouraging to manufacturers (Wright, 2013). We can only imagine the cost for an expert team of researchers at IBM to develop a single broadband radio-frequency mixer. Conversely, IBM's team used "conventional" electron beam lithography combined with a few simple chemical processes to create the circuit. This indicates that current manufacturing processes could be easily modified to produce graphene based circuits. Additionally, graphene can be derived from readily available graphite oxide by a washing process using green friendly alcohol to replace THF, dioxane, C1-C6 dialkyl ethers, phenols, ketones, et al used in electronics manufacturing (method, 2013). Ease of manufacturing and other qualities such as excellent heat tolerance that can simplify circuit designs point to graphene's future dominance in the electronics industry (Wright, 2013).
In a development parallel to IBM's, a group from UCLA has produced circuits by growing the graphene on a glass plate through chemical vapor deposition (CVD) while using an electrical field to align a single nanowire for use as a gate in the transistors (Liao, Bai et al, 2012). The group eschews the use of silicon as a limiting factor because of parasitic capacitance. In other words, the current best choice for electrical circuits is too leaky and inefficient when compared to graphene. Similar to IBM, this experiment provides performance measurements that far outshine silicon based circuits and cites inefficiencies in measurement as limiting better results. To list this development as "promising" is an understatement. The UCLA group has produced a scalable product that can be adapted to any circuit currently in use.
It is interesting to consider the dark and dirty coal as the light at the end of the tunnel for technological advancement but it is exactly that. The carbon atoms carried in a lump of coal are the same as those present in expertly designed micro-circuits. Additionally, the processes associated with creating graphene based circuits appear to counter previous electronics manufacturing proven dangerous to the environment. Altogether, the prospects for graphene to become the champion of technological advancement are great. Very soon, the diamonds lowly cousin will be worth its weight in gold.
References
Liao, L., Bai, J., Cheng, R., Zhou, H., Liu, L., Liu, Y., Huang, Y. & Duan, X. (2012, June 13) Scalable fabrication of self-aligned graphene transistors and circuits on glass. NIH Public Access. Retrieved from: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3269556/
Method of Producing Graphene Oxide and its Uses in Patent Application Approval Process. (2013). Life Science Weekly, , 2373. Retrieved from http://ezproxy.nu.edu/login?url=http://search.proquest.com/docview/1418232336?accountid=25320
Neto, A. C. & Geim, A. (2012, May 5). Graphene. New Scientist . 214( 2863), i-8.
Savage, N. (2011, June 9). First Graphene Integrated Circuit. IEEE Spectrum. Retrieved from: http://spectrum.ieee.org/semiconductors/devices/first-graphene-integrated-circuit
Wright, A. (2013, October). Tuning in to graphene. Communications of the ACM. 56(10). 15-17.
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