Graphene is an ultrathin allotrope of carbon (diamond and graphite are the other common allotropes of carbon). It consists of a single layer of sp2-bonded carbon atoms with each atom bound to three neighbors in a honeycomb structure.

Single atom thick graphene is sometimes called monolayer graphene or single-layer graphene and abbreviated as 1LG. Bilayer graphene consists of two well-defined stacked graphene layers (2LG). Few layer(s) graphene consists of three to ten well-defined stacked graphene layers (FLG).

Graphene may be synthesized from a gaseous carbon source at high temperatures using a process known as chemical vapor deposition (CVD). Another method uses a chemical process, acids, and heat to exfoliate graphite to produce graphene in a powder form. These graphene powders include graphene oxide (GO), a compound of carbon, oxygen and hydrogen) reduced graphene oxide (rGO), a compound with less oxygen and more carbon than GO; graphene nanoplatelets (GNP) short stacks of platelet-shaped graphene sheets that are identical to those found in the walls of carbon nanotubes, but in a planar form. Other carbon materials closely related to graphene include fullerenes (also known as “Bucky balls”) graphene quantum dots (GQD) and carbon nanotubes.

To understand what CVD graphene is, it is important to understand the definition of CVD. Chemical Vapor Deposition (CVD) is a process involving the high-temperature activation of gaseous hydrocarbons (e.g., methane) in the presence of a catalytic substrate, typically a copper or nickel foil. The subsequent chemical reactions deposit a thin, stable carbon lattice on the catalyst surface.

Graphene is flexible, electrically and thermally conductive, optically transparent, and impermeable.

Graphene’s unique properties stem from its atomic structure, particularly the sp2 hybridized covalent bonding of its carbon atoms, its free Pi electron availability and nanoscale thickness of 0.345 nm. As a reference, 3 million layers of graphene would be only slightly thicker than 1 mm. Graphene stacked >10 layers is technically classified as graphite. Graphene is the thinnest material known to man – so thin, in fact, that it only has two dimensions in a single-layer format. With a density of 0.77 mg/m2, it also has the highest known surface area any material.

The properties of exfoliated graphenes such as GO and rGO can vary significantly depending on the quality of the mined graphite raw material and exfoliation process used. In contrast, graphene manufactured using CVD, is largely dependent upon highly controlled and predictable industrial material inputs, including the substrate metal foils and the carbon gas precursor. Graphene recipes are designed by varying the pressures and mixtures of the gases used and because a more controllable process is utilized, the quality is generally more consistent.

While a number of factors influence graphene nucleation and growth, it is well established that CVD graphene will always have edges, nanoscale defects and grain boundaries where carbon to carbon bonding can be disrupted. The basic process for CVD graphene production on Copper and Ni is described in the diagram below.

General Graphene Corporation, a leading large-scale graphene manufacturer and supplier, has developed a series of proprietary CVD manufacturing technologies to develop CVD graphene materials.

The graphene produced on our GG 3.0 system consistently delivers D/G (defect density) ratios below 0.03 and delivers a monolayer graphene with minimal (1-5%) multilayer coverage.

However, when it comes to graphene, we believe that “good” is a relative measure – what may be “good” for one application may not perform for another. Thus, we eschew labels such as “good” because what ultimately matters most is whether the graphene performs. Graphene is not a “one size fits all material” and must be designed to consistently meet the performance needs of industry and the user.

Among the properties/characteristics with respect to which we can optimize our graphene to meet the needs of the application are:
Crystal sizes: From nm to µm to mm range
Coverage: 95% to 99.99%
Sheet Resistance: < 1000 Ω/sq down to 20 Ω/sq, depending on number of graphene layers and growth conditions.

Purchasing graphene has been difficult and incredibly expensive. However, because cost is arguably the biggest impediment to the commercialization of graphene, General Graphene’s manufacturing and graphene transfer systems were specifically designed to produce industrial scale, low-cost and consistent graphene.

At General Graphene, the graphene cost will generally be a function of volumes and the affordability of graphene in the application for which it is intended.