What is graphene?

Graphene is the most famous member of the 2D materials family: a sheet of covalently bonded carbon atoms in a hexagonal lattice in which the thickness has been reduced to a single atom. This unique nanomaterial is extraordinarily strong and has the highest known thermal and electrical conductivity. It was awarded the Nobel prize for Physics in 2010, for research done by Andre Geim and Konstantin Novoselov.

There are many other 2D materials that are being actively explored. A collective group of graphene-like structures is known as xenes – which are also monolayers of a single element. For example, single layer of black phosphorus, phosphorene, is a promising material for transistors. Other examples are silicene (silicon), germanene (germanium), and stanine (tin), all exhibiting a hexagonal structure like graphene with various degrees of buckling.

Hexagonal boron nitride (h-BN) has the same overall structure as graphene but replaces the carbon atoms with alternating boron and nitrogen atoms. Finally, members of another popular class of 2D materials are transition metal dichalcogenides with the chemical formula MX2, where M is a transition metal such as tungsten or molybdenum and X is a chalcogen such as Sulphur, selenium, or tellurium.

Interest in stacking of graphene on itself or other 2D materials is currently gaining traction. An angular or lattice mismatch has been shown to create different electrical properties of the layered stack. This opens the door to creating new devices in a bottom-up approach, stacking multiple layers of 2D materials under such angles that allow tuning of the properties. However, as relaxation processes after deposition occur, control measurements are needed to verify the angular mismatch between the layers.

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