Reference

Graphene Glossary

A comprehensive glossary of graphene terminology — from production methods and material types to characterization techniques and industry standards.

A

AFM (Atomic Force Microscopy): A technique that measures surface height, used to determine flake thickness and layer number. See also: How graphene is characterized
Agglomerate: A cluster of particles or flakes stuck together. The main enemy of performance in composites. See also: The dispersion problem
Aspect Ratio: Lateral size divided by thickness. High aspect ratio drives reinforcement and barrier performance.

B

Bandgap: An energy range electrons cannot occupy. Graphene has none, which is why it cannot easily act as a digital switch.
BET Surface Area: Specific surface area measured by gas adsorption, in m²/g. A practical indicator of how far a material is from monolayer graphene.
Bilayer Graphene: Two stacked layers of graphene, which can be arranged in AB (Bernal) or twisted configurations. Bilayer graphene can develop a tunable electronic bandgap when an electric field is applied perpendicular to the layers, unlike monolayer graphene which remains gapless.

C

C/O Ratio: Carbon-to-oxygen ratio. Low values mean heavy oxidation (graphene oxide); high values mean little oxygen.
Chemical Vapor Deposition (CVD): A scalable production method in which a carbon-containing gas (typically methane) is decomposed at high temperature (900-1050 °C) on a catalytic metal substrate — usually copper or nickel — to grow large-area, high-quality graphene films. See also: How graphene is made
Compatibilizer: An additive that helps a filler bond with a polymer.

D

D, G, and 2D Peaks: Key features of the Raman spectrum. The D peak indicates defects; the 2D peak shape indicates layer number. See also: Raman quality control
Defect Density: How many disruptions exist in the carbon lattice, often estimated from the Raman D/G ratio.
Dirac Fermion: Charge carriers in graphene that behave as massless relativistic particles, obeying the Dirac equation rather than the Schrödinger equation. This gives graphene its exceptionally high electron mobility, exceeding 200,000 cm²/V·s in suspended samples.
Dispersant: A chemical that helps keep flakes separated in a liquid or polymer.
Dispersion: Either the process of separating flakes or a liquid product containing separated flakes.

E

Edge Functionalization: Attaching chemical groups only at flake edges, preserving the basal plane.
Electrochemical Exfoliation: Separating graphite layers using an electric current and electrolyte.
Exfoliation: The process of separating individual graphene sheets from bulk graphite by overcoming the van der Waals forces between layers. Exfoliation can be performed mechanically (e.g., tape method), in liquid media, or through chemical intercalation and oxidation. See also: Exfoliation methods

F

Few-Layer Graphene (FLG): Graphene material consisting of 2 to approximately 10 stacked layers. FLG retains many of graphene's enhanced properties while being easier and cheaper to produce at scale than monolayer graphene, making it the most common form in commercial applications.
Flash Graphene: Graphene made by rapidly heating carbon-containing material with an electrical discharge (flash Joule heating). See also: Flash graphene
Functionalization: Adding chemical groups to graphene to change how it interacts with other materials. See also: Graphene functionalization

G

Gauge Factor: Sensitivity of a strain sensor: relative resistance change per unit strain.
Graphene: A single atomic layer of carbon atoms arranged in a two-dimensional hexagonal (honeycomb) lattice. Graphene exhibits extraordinary electrical conductivity, thermal conductivity (~5,000 W/m·K), mechanical strength (~130 GPa tensile strength), and optical transparency (~97.7%). See also: What is graphene?
Graphene Nanoplatelet (GNP): Short stacks of graphene sheets (typically 1-15 nm thick, up to 25 μm in lateral dimension) produced by exfoliation of graphite. GNPs are among the most commercially available graphene materials and are widely used as fillers in polymer composites, coatings, and energy storage devices.
Graphene Oxide (GO): A chemically modified form of graphene with oxygen-containing functional groups (hydroxyl, epoxide, carboxyl) attached to the basal plane and edges. GO is hydrophilic and dispersible in water, making it useful as a precursor for solution-processed graphene films, but its electrical conductivity is significantly reduced compared to pristine graphene.
Graphene Quantum Dots (GQDs): Very small graphene fragments, typically a few nanometers across, with optical properties such as fluorescence.
Graphite: Bulk stacked layers of graphene. The usual starting material for bulk graphene. See also: Graphite supply chain risk

H

Hexagonal Boron Nitride (h-BN): A graphene-like 2D material that conducts heat but insulates electrically.
Hummers Method: The most widely used chemical process for producing graphene oxide, involving the oxidation of graphite using a mixture of sulfuric acid, sodium nitrate, and potassium permanganate. Modified versions of this 1958 method remain the industrial standard for large-scale GO production.

I

Interface: The boundary between graphene and the surrounding material. Where most graphene benefits are won or lost.

L

Lateral Size: The width of a flake across its face, usually given in micrometers.
Layer Number: How many graphene layers make up a flake. Best reported as a distribution.
Liquid-Phase Exfoliation (LPE): A scalable technique that uses ultrasonic energy or high-shear mixing to separate graphene layers from graphite dispersed in a solvent. LPE typically produces few-layer graphene flakes and avoids the chemical damage associated with oxidation routes, though flake sizes are generally smaller (sub-micron to a few microns). See also: Graphene manufacturing

M

Masterbatch: A concentrated mix of graphene in a carrier polymer, diluted during processing.
Moiré Pattern: A larger repeating pattern formed when two lattices are overlaid with a twist; central to magic-angle graphene.
Monolayer Graphene: A single, one-atom-thick sheet of sp²-bonded carbon — the strictest definition of graphene per ISO/TS 80004-13. Monolayer graphene exhibits the material's theoretical maximum properties and is typically produced by CVD on metal catalysts or by mechanical exfoliation of highly oriented pyrolytic graphite.
MXene: A family of conductive 2D metal carbides and nitrides.

N

Nanoform: A regulatory term (notably under EU REACH) for a nanoscale form of a substance with specific characteristics. See also: Graphene and REACH

P

PECVD: Plasma-Enhanced Chemical Vapor Deposition — a variant of CVD that uses plasma energy to decompose precursor gases at lower substrate temperatures (300-700 °C instead of ~1000 °C). PECVD enables direct graphene growth on non-catalytic substrates such as glass and polymers, potentially eliminating the need for a transfer step.
Percolation Threshold: The loading at which conductive particles first form a connected network, causing a sharp rise in conductivity.
Pristine Graphene: Graphene with few defects or added chemical groups.

R

Raman Spectroscopy: The primary analytical technique for characterizing graphene, using inelastic scattering of laser light to identify the material's vibrational modes. The G peak (~1580 cm⁻¹), 2D peak (~2700 cm⁻¹), and D peak (~1350 cm⁻¹) reveal layer count, defect density, and stacking order, making Raman the standard quality-control tool in graphene production. See also: Standards & testing
Reduced Graphene Oxide (rGO): Graphene oxide that has been chemically, thermally, or electrochemically treated to remove most oxygen-containing groups and partially restore the sp² carbon network. rGO recovers significant electrical conductivity but retains residual defects and functional groups, resulting in properties between GO and pristine graphene.
Restacking: Separated flakes coming back together, losing surface area.
Roll-to-Roll: A continuous, high-throughput manufacturing process in which CVD graphene is grown on a metal foil fed through a furnace on rollers, then transferred to a target substrate in a continuous operation. Roll-to-roll processing is critical for scaling graphene production to industrial volumes for applications such as transparent conductive films and flexible electronics. See also: Scaling production

S

Sheet Resistance: A measure of a thin film's electrical resistance independent of its thickness, expressed in ohms per square (Ω/sq). High-quality monolayer CVD graphene typically achieves sheet resistance of 125-500 Ω/sq, compared to 10-100 Ω/sq for indium tin oxide (ITO), making it a key metric for transparent conductor applications.
sp² Bonding: The hybridization state of carbon atoms in graphene, in which each carbon forms three sigma bonds with neighboring atoms in a trigonal planar arrangement, with one remaining p-orbital electron contributing to a delocalized π-electron system. This bonding geometry gives graphene its planar hexagonal structure and enables its exceptional electrical and thermal conductivity.
Specific Surface Area: Surface area per unit mass (see BET Surface Area).
Surfactant: A molecule that stabilizes particles in liquid by coating their surfaces.

T

Technical Data Sheet (TDS): A supplier document describing typical properties of a product. See also: How to read a data sheet
Technology Readiness Level (TRL): A standardized scale from 1 (basic research) to 9 (proven in operational environment) used to assess the maturity of a technology. In the graphene industry, most composite and coating applications have reached TRL 7-9, while semiconductor and biomedical applications are typically at TRL 3-5. See also: Market readiness
TEM (Transmission Electron Microscopy): High-resolution imaging used to examine flakes and count layers.
Tortuous Path: The longer route gases or liquids must take around aligned platelets, the basis of barrier improvements.
Transfer (CVD graphene): The process of detaching a CVD-grown graphene film from its metal catalyst substrate and placing it onto a target substrate (e.g., SiO₂/Si, polymer, glass). Common methods include PMMA-assisted wet transfer and direct dry lamination; the transfer step remains a major source of defects, wrinkles, and contamination in CVD graphene production.
Turbostratic: Stacked layers with random rotations between them, which separate more easily than ordered graphite.
Twisted Bilayer Graphene: Two layers stacked with a deliberate small rotation, producing unusual electronic states.
Two-Dimensional (2D) Material: A material only one or a few atoms thick, such as graphene, hexagonal boron nitride, or molybdenum disulfide. See also: Beyond graphene: other 2D materials

V

Van der Waals Forces: Weak, distance-dependent intermolecular forces arising from transient dipole interactions between atoms. In graphite, van der Waals forces hold the graphene layers together with an interlayer binding energy of approximately 2 eV/nm², which is strong enough to maintain the layered structure yet weak enough to allow mechanical exfoliation into individual sheets. See also: Graphene fundamentals

X

XPS (X-ray Photoelectron Spectroscopy): A surface technique measuring elemental composition and chemical bonding, used for C/O ratios.