Graphene Growth
By Thomas J. Beck
With the physical limitations of silicon based electronics quickly approaching, the search for the next generation is rapidly intensifying. Graphene’s impressive mechanical and electrical properties make it a promising choice for future electronics not only as a device material, but also as an interconnect.
Carbon based electronics have been gaining interest since the discovery of the buckyball in 1985. The subsequent discovery of carbon nanotubes in the early 90’s has led to carbon based devices ranging from transistors[1] to baseball bats.[2] This carbon based electronics research, which is still thriving today, continues to offer promising advances in electronics. As a truly 2D material, graphene has been of theoretical significance for more than 60 years.[3] The discovery of graphene as a free-standing material in 2004, by Geim and Novoselov,[4] proved that this 2D material was not merely a theoretical toy but something tangible which can be exploited for its unique properties. Graphene is essentially the mother of all graphitic materials. It can be formed into buckyballs and nanotubes, etched into nanoribbons, or stacked into bulk graphite. The properties of graphene that have researchers excited include its high mobility, ballistic transport, and a width dependent band gap. Graphene also has the upper hand over carbon nanotubes in that it can be produced as a single two-dimensional sheet, making it easy to manipulate and pattern allowing it to be integrated into current production methods.
There are three primary methods through which graphene is being produced. The first, the “scotch tape” method, involves mechanically cleaving a piece of bulk graphite using tape. This method has its advantages and has proven to produce samples with low contamination. It also allows for testing the limits of graphene’s capabilities. However, it is a time consuming process and is not a suitable method for production. The second method, epitaxial growth on SiC via Si sublimation, pioneered by Walt deHeer at GA Tech shows much more promise for grown graphene based electronic devices.[5] The third is Chemical Vapor Deposition (CVD) which has been undertaken by several groups with mixed success. CVD processes tend to be prone to contamination, which, when dealing with a 2 dimensional material, causes drastic changes to its properties.
[1] Postma, Henk W. Ch.; Teepen, Tijs; Yao, Zhen; Grifoni, Milena; Dekker, Cees (2001). “Carbon Nanotube Single-Electron Transistors at Room Temperature” Science 293 (5527): 76.
[2] Easton Sports press release (http://www.eastonsports.com/corporate/PressReleases/168.htm)
[3] Wallace, P. R. The band theory of graphite Phys. Rev. 71, 622–634 (1947)
[4] K.S. Novoselov, A.K. Geim, S.V. Morozov, D. Jiang, Y. Zhang, S.V. Dubonos, I.V. Grigorieva, A.A. Firsov, Science 306 (2004) 666.
[5] Claire Berger, Zhimin Song, Tianbo Li, Xuebin Li, Asmerom Y. Ogbazghi, Rui Feng, Zhenting Dai, Alexei N. Marchenkov, Edward H. Conrad, Phillip N. First, and Walt A. de Heer, J. Phys. Chem. 108, 19912-19916(2004)
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#1 by Edward H Conrad at June 4th, 2009
I would like to point out two important errors in this website. First, graphene was not discovered by Geim! It was discovered in 1975 by von Bommel and in 1999 (well before Giem) it was shown how graphene could be isolated by Forbeaux. I would be happy to give you the relevant references. It seems a little odd that the work by de Heer was never referenced even though he is a GT faculty.
The second point is that exfoliated graphene is not of better quality. Again I would be happy to give you the relevant numbers. Epitaxial graphene can now be easily controlled, made to grow over many inches and has order of magnitude better physical properties.
Sincerely,
Ed Conrad
#2 by tbeck at June 4th, 2009
This article is meant to be a very general overview of graphene growth processes. I apologize for the confusion over the discovery of graphene - I understand Geim did not discover it however, it is my understanding, that he was the first to isolate it as a free standing material. I have re-worded the text to be more specific to this. Walt de Heer and his group have done great work on graphene growth but I wrote this article as a general overview of growth techniques. I only include Geim’s work because I feel this work was important in showing graphene could be isolated and be used as an electronic material.
On the second point, I did not intend to claim that exfoliated graphene is of any better quality. I have given a basic overview of three methods currently being investigated and given some pros and cons to each. I intentionally did not draw conclusions as to which method produces superior graphene. I have left this up to the reader to further investigate on his/her own.
Thank You for your Comments,
TJ Beck