Graphene Production and Properties

Study Notes

Graphene can be produced using two methods: Mechanical Exfoliation and Chemical Vapor Deposition
Mechanical exfoliation involves using scotch tape to peel off layers of graphite
Chemical Vapor Deposition (CVD) uses methane as a carbon source in a hydrogen environment to grow graphene epitaxially on silicon carbide or metal surfaces
Roll-to-roll production of 30-inch graphene films enables large-scale production of graphene for transparent electrodes

Pristine graphene is a semi-metal with zero bandgap
Graphene's Fermi level can be tuned by electrical or chemical doping
Electrical doping tunes the Fermi level, while chemical doping can also open up a bandgap and tune the Fermi level
Graphene exhibits high electron mobility at room temperature, a desirable property for electronic devices
Graphene has an optical transmittance control property, allowing for its use as a transparent electrode
Single-layer graphene absorbs 2.3% of light
Graphene boasts exceptional mechanical strength, suitable for flexible and stretchable devices
Graphene's Young's modulus is 1 terapascal (TPa), making it exceptionally strong
Graphene possesses a low density of 2 g/cm3 and a high specific surface area, approaching its theoretical limit of 2630 m2/g
Graphene is very resistant to fracture, with a tensile strength of 130 gigapascals (GPa)
Graphene is an excellent thermal conductor with a thermal conductivity exceeding 4800 W/m/K due to its unique phonon effects
Graphene's electrical properties include high electron mobility up to 15000 cm2/Vs and exhibits the quantum Hall effect

Fullerenes are molecules composed of carbon atoms arranged in a spherical, ellipsoidal, or tubular structure
The smallest fullerene is C20, while larger ones exist up to C300
The most common fullerene is C60
Various isomers of fullerenes exist, with C20, C24, C28, C32, C36, and C50 being notable examples

C60 has a structure resembling a truncated icosahedron, similar to a soccer ball
C60 contains 20 hexagons and 12 pentagons
C60 exhibits sp2 bonds on its spherical surface and weaker pi bonds within the orbitals perpendicular to the surface
The diameter of C60 is 0.71 nanometers
Fullerenes are stable molecules, but not entirely unreactive
Fullerenes are soluble in aromatic solvents
Fullerenes exhibit superconductivity
Fullerene's electronic properties include a band gap, which is influenced by the fullerene size and substrate
The band gap of fullerene is comparable to the electronic band gap observed in bulk semiconductors
Changing the size of the fullerene or the substrate can modify the band gap of fullerene molecules

The HOMO-LUMO (Highest Occupied Molecular Orbital – Lowest Unoccupied Molecular Orbital) gap of fullerene varies depending on the molecule and its environment
The HOMO-LUMO gap can range from 1.75 eV for free C60 to 2.7 eV for C60 on a gold (Au) substrate.