No single method dominates. The right choice depends on whether the goal is a single flawless flake for a physics experiment, wafer-scale film for electronics, or tons of graphene nanoplatelets for a composite or coating. The first five methods below are defined in ISO/TS 80004-13; the remainder are widely used industrial and lab routes described in the graphene production literature.
Defined by ISO as "detachment of separate/individual 2D material layers from the body of a material via mechanical methods." The best-known version is peeling — the "Scotch-tape method" or micromechanical cleavage — repeatedly splitting graphite crystals with adhesive tape until single layers remain, which is how graphene was first isolated in 2004. A second route is dry-media ball milling, which shears bulk graphite between milling media.
Bulk layered material (typically graphite) is exfoliated in a solvent using hydrodynamic shear forces — generated by ultrasonic cavitation or high-shear mixing — that peel layers apart in suspension. A surfactant is often added in aqueous dispersions to promote exfoliation and keep flakes from restacking. Output is typically a dispersion of few-layer graphene and graphene nanoplatelets rather than single, large monolayers.
ISO defines CVD generally as "deposition of a solid material by chemical reaction of a gaseous precursor or mixture of precursors, commonly initiated by heat on a substrate." For graphene, a hydrocarbon gas (commonly methane) decomposes at high temperature on a metal substrate — most often copper foil — where carbon atoms assemble into a continuous graphene layer. The film is then typically transferred off the metal onto the target substrate (e.g., glass, silicon, flexible polymer).
Defined as CVD growth of a 2D material "upon a continuous substrate that is processed as a rolled sheet, including transfer of a 2D material(s) to a separate substrate." This is CVD graphene scaled to an industrial, continuous production line — copper foil unspools through a furnace for growth, then through a transfer stage, rather than being processed as individual batches.
A silicon carbide (SiC) substrate is heated under controlled high-temperature conditions so silicon atoms near the surface sublimate away, leaving behind a carbon-rich surface that reorganizes into graphene layers directly on the substrate. ISO reserves the term epitaxial graphene specifically for graphene grown this way on SiC — graphene grown by epitaxy on other substrates (e.g., Ni(111)) is not called "epitaxial graphene" under the standard's usage.
Graphite is chemically oxidized (commonly via a Hummers-method-type process) into graphite oxide, then exfoliated into single sheets of graphene oxide (GO) — a heavily oxygen-functionalized, single-layer material (C/O atomic ratio roughly 2:1). GO is electrically insulating in its native form, so it is usually converted to reduced graphene oxide (rGO) by chemical, thermal, microwave, photo-chemical, or microbial reduction, which restores much (not all) of graphene's sp² bonding and conductivity.
A controlled explosion is used to build graphene directly from a gas-phase reaction. A hydrocarbon gas — commonly acetylene (C₂H₂) mixed with oxygen — is loaded into a closed detonation chamber and ignited, often with nothing more than a spark plug. The detonation wave heats the gas to roughly 2,500 K within microseconds and breaks the acetylene apart by collision into H atoms and carbon-bearing radicals (ethynyl, vinylidene), which recombine as the chamber cools into stacked hexagonal carbon sheets that condense out as soot.
The oxygen-to-carbon (O/C) ratio of the gas mixture controls the product: low O/C mixtures (O/C ≈ 0.25) yield a low-density, aerosol-like gel of thin stacks — roughly 8 weakly bonded turbostratic layers spanning 20–30 nm — while higher O/C mixtures (O/C ≈ 0.75) give a denser powder of thicker stacks, around 30 layers spanning 100–200 nm. In both cases the layers come out turbostratically stacked rather than in Bernal registry, because they condense from a gas-phase reaction rather than growing epitaxially layer-by-layer.
The appeal is speed and cost: a single detonation converts gas to graphene-family material in a fraction of a second, using cheap, simple equipment — no vacuum furnace, no metal catalyst foil, no solvent. Kansas State University researchers demonstrated a version using just hydrocarbon gas, oxygen, and a spark plug, positioning it as a low-cost, scalable route to bulk graphene-family powder rather than a way to make pristine, large-area monolayers.
Arc discharge: a high-current arc struck between graphite electrodes in an inert or reactive atmosphere vaporizes carbon, which recondenses into few-layer graphene sheets alongside other carbon nanostructures (soot, nanotubes, fullerenes) that must be separated out.
Unzipping carbon nanotubes: a multi-walled carbon nanotube is longitudinally cut open (oxidatively or by plasma etching) to unroll into a graphene nanoribbon — useful for producing narrow, ribbon-shaped graphene with tunable width-dependent electronic properties.
| Method | Typical output | Scale | Best fit |
|---|---|---|---|
| Mechanical exfoliation | Pristine single flakes, µm-scale | Lab-scale only | Fundamental research |
| Liquid-phase exfoliation | Few-layer flake dispersions | Bulk / industrial | Inks, coatings, composites |
| CVD | Continuous monolayer film | Wafer to sheet | Electronics, sensors |
| Roll-to-roll CVD | Continuous monolayer film | Meters, continuous | Displays, flexible devices |
| Epitaxial growth (SiC) | Substrate-bonded film | Wafer-scale | RF/high-freq electronics |
| Graphite oxide → rGO | Defect-rich sheets/powder | Bulk, low cost | Batteries, membranes, composites |
| Detonation synthesis | Turbostratic stacked powder/gel | Bulk, very fast | Composites, energy storage |
| Arc discharge | Few-layer sheets + byproducts | Small batch | Nanocarbon research |
| CNT unzipping | Graphene nanoribbons | Small batch | Nanoribbon electronics |