A simpler, cheaper, scalable method of making high quality graphene
By Darren Quick
March 3, 2011
Any regular reader of this site will be aware of the huge potential of graphene – the chicken-wire-like lattice of carbon atoms arranged in thin sheets a single atomic layer thick that promises to revolutionize the fields of data storage, energy storage and computer chips, just to name a few. But for this potential to be fully realized, meaningful quantities of the material need to be produced economically and at a consistent quality. Current graphene manufacturing processes are complicated and generally offer unpredictable results regarding the material's quality. Now a research team from the University of Pennsylvania has succeeded in creating high quality graphene using readily available materials and manufacturing processes that can be scaled up to industrial levels.
Although graphene is relatively easy to create in small quantities with it likely that a small amount of graphene is made every time a pencil is used, putting a million monkeys to work scribbling away for a million years probably isn't the best way to go about producing the material. While some recent studies report processes capable of creating high-quality graphene that is just a single atom thick over around 90 percent of its area, the Penn research team has been able to push it closer to the ultimate goal of 100 percent by achieving a figure of over 95 percent.
Chemical vapor deposition (CVD), which involves blowing methane over thin sheets of metal so that the carbon atoms in the methane form a thin film of graphene on the metal sheets, is seen as one of the more promising graphene manufacturing methods. But to prevent multiple layers of carbon from accumulating into unusable clumps the process must be done in a near vacuum, which increases its cost.
The process developed by the Penn researchers is more cost effective and flexible as it allows single-layer-thick graphene sheets to be reliably produced at atmospheric pressure, providing the metal sheets are smooth enough. Because defects in the surface can cause the graphene to accumulate in unpredictable ways, other methods involve a costly process to prepare expensive custom copper sheets to get them as smooth as possible.
However, for their experiment the Penn team used commercially available copper foil and "electropolished" it, which is a common industrial technique used in finishing silverware and surgical tools. The resultant polished foil was smooth enough to produce single-layer graphene over 95 percent of its surface area. By using commercially available materials and chemical processes that are already used in manufacturing the team says it has developed an overall graphene production system that is simpler, less expensive and more flexible – particularly for future graphene assembly lines.
"If you need to work in high vacuum, you need to worry about getting it into and out of a vacuum chamber without having a leak," said the study's principal investigator, A.T. Charlie Johnson, professor of physics. "If you're working at atmospheric pressure, you can imagine electropolishing the copper, depositing the graphene onto it and then moving it along a conveyor belt to another process in the factory."