16 January 2018
Published online 24 April 2017
Researchers show that a very thin layer of graphene can be “invisible” to an underlying growing crystal.
Coating a substrate by a layer of graphene does not interfere with its ability to continue to guide crystal growth, according to a new Nature study1.
The process by which crystals are grown on top of a substrate, or what the scientists refer to as epitaxy of materials such as gallium arsenide (GaAs) is widely applied in the manufacture of optoelectronics such as LEDs and lasers.
For such substrate-guided growth to be possible, however, the surface of the substrate has to be completely homogeneous and free of impurities. Now, scientists have discovered that coating the surface of the substrate with a single layer of graphene (a carbon layer in which each carbon atom is bonded to only three other carbons) does not interfere with epitaxy.
That is to say, the crystals grow on top of the substrate right through the graphene, as if the graphene layer wasn’t there.
The team laid a sheet of graphene on top of a GaAs substrate, and used a combination of X-ray diffraction and electron microscopy to show that epitaxy was unhindered by the interposed graphene layer, even down to the atomic level.
The advantage of this is not restricted to surface protection. The thin films that start growing above the graphene layer can also be removed relatively easily by mechanical exfoliation, to produce thin and bendable semiconductors. Additionally, substrates, which can be expensive, can be reused.
The discovery’s potential lies in the production of flexible electronics and lowering the cost of manufacturing.
- Yunjo, K. et al. Remote epitaxy through graphene enables two-dimensional material-based layer transfer. Nature 544, 340–343 (2017).