Graphene

$\ce{C}$ atoms arranged to a hexagonal network. 2D crystal based. Has $3$ fold symmetry. Single sheet of graphite.

Unit Cell

• A rhombus with $120°$
• Lattice parameter (side length of a unit cell) $a=2d\cos{30}°=\sqrt3 d$ where $d$ is the $\text{C}-\text{C}$ bond length
• 2 atoms per unit cell

Note

Single layer of graphene was discovered using scotch tape method and the discovery won a Nobel prize in 2010.

Synthesis

• Top-down approaches
  • Exfoliation (eg: Scotch tape method)
• Bottom-up approaches
  • Chemical vapor deposition

Properties

• Band gap is $0$
• High tensile strength ($\sim 1100\;\text{GPa}$)
• High young’s modulus ($\sim 1\;\text{TPa}$)
• High charge carrier mobility ($\sim 2$)
• Highly transparent ($97\%$)