Oxford researchers find a way to grow defect-free graphene using CVD

Researchers from Oxford University has found a new way of growing defect-free graphene using CVD. Defects weaken the material and prevent electronics from flowing freely through it, and this method could pave the way toward large-scale graphene production.

Graphene domains across grain boundariesGraphene domains across grain boundaries

The researchers say that the random graphene flakes which are formed during the CVD process can be lined up by manipulating the alignment of carbon atoms on a relatively cheap copper foil. In fact the atomic structure of the copper surface acts as a 'guide' that controls the orientation of the carbon atoms growing on top of them. By combining the control of the copper foil and the pressure applied during growth makes it possible to control the thickness of these domains, the geometry of their edges and the grain boundaries where they meet.

New research into graphene grain boundaries

Researchers from the Beckman Institute have researchers the electronics behavior of graphene with grain boundaries. They explain that when graphene is grown, lattices of the carbon grains are formed randomly, linked together at different angles of orientation in a hexagonal network. But sometimes when the process is not perfect, defects called grain boundaries (GBs) form. These boundaries scatter the flow of electrons in graphene, which harms the material's electronic performance.

The researchers grew polycrystalline graphene on a silicon wafer using CVD, and then examined the atomic-scale grain boundaries using scanning tunneling microscopy and spectroscopy. The electron scattering at the boundaries significantly limits the electronic performance compared to grain boundary free graphene.  In fact they say that when the electrons' itinerary takes them to a grain boundary, it is like hitting a hill - the electrons bounce off, interfere with themselves and create a wave pattern. The hill slows the electrons down - which means that the grain boundary is a resistor in series with a conductor.

Defects in Graphene can make it even stronger

NIST researchers say that defects in Graphene may appear due to the movement of the carbon atoms at high temperatures when producing graphene by heating silicon carbide under ultrahigh vacuum. Graphene tend to rearrange from six-sided rings to five or seven atoms. Stringing five and seven member rings together in closed loops creates a new type of defect or grain boundary loop in the honeycomb lattice. These defects might allow it a little flexibility, making Graphene even more resilient to tearing or fracturing.

The researchers say that we should be able to either avoid defects entirely or produce them at will by variations in growth conditions.

Researchers study graphene grain boundaries and create beautiful images

Researchers from Cornell are studying Graphene grain boundaries. The researchers say that graphene doesn't grow in perfect sheets - it rather develops in pieces that resemble patchwork quilts. The meeting point of those patches is called grain boundaries, and the researchers are studying those boundaries.

The researchers grew Graphene on copper and then conceived a novel way to peel them off as free-standing, atom-thick films. They imaged the graphene (using diffraction imaging electron microscopy) and used a color to represent the angle that electrons bounced off at. Using different colors based on the electron bounce they created an easy way to image graphene grain boundaries. This method could also be applied to other 2D materials - and help explain the way that Graphene was stitched together at the boundaries.