A new way to make higher quality bilayer graphene

(Phys.org)—A team of researchers with members from institutions in the U.S., Korea and China has developed a new way to make bilayer graphene that is higher in quality than that produced through any other known process. In their paper published in Nature Nanotechnology, the team describes the technique they developed and the possible uses for the bilayer graphene that is produced.

Graphene is, of course, a flat material made from just single carbon atoms; it forms in a honeycomb pattern and has been found to have excellent electrical properties—one hindrance to using graphene in many applications has been the lack of a bandgap. That hindrance was partially overcome back in 2009 when a team working in the U.S. found that creating two layers of graphene bonded together and then applying electricity could cause a bandgap to occur. Since that time, researchers have been looking for ways to create such bilayer graphene in a way that could be commercialized. In this latest effort, the researchers report on a new technique they have developed that they claim produces the highest quality bilayer graphene yet.

The current method used to create graphene is to use chemical vapor deposition—in creating bilayer graphene, researchers have to make sure that the two layers are in proper alignment with one another, outcomes are typically labeled mis-oriented or of a Bernal-type—the latter is obviously the outcome desired with the result called an AB-stacked configuration. The new technique developed by the team results in just such a configuration, it involves allowing a small amount of oxygen to enter a vapor deposition chamber where the graphene is being grown—the oxygen combines with a copper foil substrate causing a disassociation between methane molecules, releasing carbon atoms which then diffuse through the foil causing a second layer of graphene to form.

The team reports that the electrical properties of the resultant material is comparable to graphene produced from graphite, and it has a band gap of approximately 125meV, which the team acknowledges is not high enough for making transistors—but, they note it would likely work very well in optical applications such as for creating tunable photoemitters and/or detectors.