Graphene Gets Scalability

Graphene’s unique properties include ultra-high electrical conductivity and tensile strength. The downside is that it’s dirty.

Researchers at Columbia University, the University of Montreal, and NIST are cleaning up graphene using an oxygen-free chemical vapor deposition (OF-CVD) method to create high-quality graphene samples at scale. Their work, published in Nature, demonstrates how trace oxygen affects the growth rate of graphene and identifies the link between oxygen and graphene quality for the first time.

Graphene has historically been synthesized in one of two ways. There’s the “scotch-tape” method, in which individual layers are peeled from a bulk sample of graphite (the same material you’ll find in pencil lead) using household tape. Such exfoliated samples can be quite clean and free from impurities that would otherwise interfere with graphene’s desirable properties. However, they tend to be too small—just a few tens of micrometers across–for industrial-scale applications and, thus, better suited for lab research.

Approximately 15 years ago, researchers developed a method to synthesize large-area graphene. Known as CVD growth, a carbon-containing gas, such as methane, is passed over a copper surface at a temperature high enough (about 1000 °C) that the methane breaks apart and the carbon atoms rearrange to form a single honeycomb-shaped layer of graphene. CVD-synthesized samples, however, suffer from problems with reproducibility and variable quality.

Improvements in the methods took place, but they were still lacking until now. The team found that when trace oxygen was eliminated, CVD growth was much faster, with the same results every time. They also studied oxygen-free CVD graphene growth, finding that a simple model could predict growth rate over a range of different parameters.

Now, the team plans to develop a method to cleanly transfer their high-quality graphene from the metal growth catalyst to other functional substrates such as silicon.