Double-layer graphene – a kind of graphene, formed by two closely spaced graphene layers. Double-layered graphene has unique properties that opens up new applications for graphene materials.
Double-layer graphene – a kind of graphene, formed by two closely spaced graphene layers. The graphene layers located at a distance of less than 1 nm from each other. Electrons of single layer graphene can tunnel to the other layer.
Because graphene itself has unique properties, bilayer graphene also has unusual properties that are different from “single-layer” graphene.
Fig. 1. AA type and AB type double-layer graphene
One of the unique properties of graphene is the high mobility of electrons. Electrons and holes (places for electrons) in graphene easily and quickly move under the action of external electric field. Have a single-layer graphene there is no forbidden zone (forbidden energy States for electrons), so the hole cannot be closed. Graphene via conventional current always flows.
The advantage of bilayer graphene is the ability to create a locally restricted area and to manage its value. This unique property will allow its use in microelectronics (production of a new generation of transistors, etc.) and optics.
Another unique property of bilayer graphene is that under pressure becomes incredibly hard and durableas diamond, which makes it possible to use in flexible body armor.
There are three main types of double-layer graphene:
– AA type – a lattice sites, which is a hexagon, two layers of graphene are exactly above each other,
– AB type – the second graphene layer is deployed on 60° relative to the first,
handlebar type double-layer graphene, the two layers are rotated relative to each other by an arbitrary angle.
Fig. 2. Type twisted double-layer graphene
Each of these types of double-layer graphene has its own characteristics that scientists still have to learn.
So, scientists have established that the rotation of the graphene layers relative to each other at the “magic angle” (which is close to 1.1 degrees) and a temperature close to absolute zero, it is superconductivity. The critical temperature for two-layer graphene is about 1.7 Kelvin and a critical magnetic field of about 0.05 Tesla (500 Gauss) However, if you change “magic angle” (i.e., when the rotation of the graphene layers relative to each other at different angle) the superconductivity disappears.