When graphene production was on the cusp of realization in 2004, it was considered a mechanical novelty with limited practical or commercial applications. Literature exploring the underlying theory of two-dimensional materials spans back to the mid-20th Century. Yet it was exclusively hypothetical and confined to academic fields until monolayer graphitic sheets were first exfoliated using adhesive tape. Physicists used multiple exfoliation steps to sequentially split layers of graphene until a monomolecular layer was left behind, the flakes of which were then deposited onto a silicon substrate. This was verified using atomic force microscopy (AFM), which illuminated the unique functional properties of graphene sheets.
Graphene production subsequently received enormous marketing exposure which led to ongoing media hyperbole. However, it remains a relatively immature technology that is gradually expanding towards true commercial viability. This is supported by numerous innovations in both exfoliation and epitaxial graphene production techniques.
Despite the high functionality of graphene produced through exfoliation, the low throughput and time-consuming nature of exfoliant graphene transfer limits its commercial viability. Significant research into epitaxial graphene production yielded positive results within five years of the material’s debut, with the introduction of graphene growth through chemical vapor deposition (CVD).
CVD Graphene Production
CVD has emerged as one of the most important tools in graphene production as it enables large-area graphene sheets to be grown on substrate materials, rather than the flakes that commonly emerge through exfoliation. This is achieved by flowing reactant gases or vapors across a heated crystalline substrate in ultra-high vacuum (UHV) conditions. The bonding affinity between carbon molecules and the substrate was determined to be critical in achieving the unique electronic band structure of two-dimensional graphene.
This need for a growth substrate perpetuated the end-use applicability issues of graphene, carrying over the so-called ‘transfer issue’ from exfoliation graphene production techniques. However, further research into suitable crystalline growth surfaces discovered numerous substrates capable of facilitating epitaxial growth of functional graphene sheets. Silicon carbide (SiC), platinum (Pt) nickel (Ni), cobalt (Co), copper (Cu). The potential intermediary surfaces for graphene production are myriad, with more emerging from ongoing studies.
The steady progression of CVD graphene production was limited by scalability issues, however. It was difficult to reconcile the volume of copper consumed per gram of graphene through roll-to-roll manufacturing, for example. Metal-assisted exfoliation (MAE) aimed to alleviate these issues by transferring graphitic films from a copper substrate onto a flexible surface with significantly reduced levels of copper consumption due to the comparative lack of corrosive intermediates. It is one of the leading techniques for sustainable graphene production with demonstrable improvements in material yield while enabling reuse of copper substrates.
Graphene Production with Grolltex
Grolltex is one of the leading manufacturers of CVD-generated graphene, producing high-quality films at angstrom scales on copper and transferring single layer materials to silicate and other substrate materials. We have devoted significant resources toward eliminating the need for ‘sacrificial’ copper substrates from graphene production through our patented transfer technologies, which has translated into more cost-effective and sustainable graphene production than anywhere else in the world. We help make single-layer graphene ‘industrializable’.