Researchers have achieved a leap forward in graphene production, from a technique that synthesizes a few square centimeters of single-crystal graphene in a couple of hours, to an optimized method that allows the creation of an almost-perfect (over 99.9 percent aligned) 5 × 50 cm2 single-crystal graphene in just 20 minutes.
The low production costs, comparable to commercially available lower quality polycrystalline graphene films, could expand its usability. The method is expected to stimulate further fundamental work on graphene and related materials, including large scale folding of graphene sheets, similar to paper, creating origami-like or kirigami-like shapes, which could be applied to future flexible circuits.
A foundation of the modern technology that uses single-crystal silicon has been the growth of high-quality single-crystal Si ingots with diameters up to 12 inches or larger. For many applications of graphene, large-area high-quality (ideally of single-crystal) material will be enabling. Since the first growth on copper foil a decade ago, inch-sized single-crystal graphene has been achieved. We present here the growth, in 20 min, of a graphene film of (5 × 50) cm2 dimension with over 99% ultra-highly oriented grains. This growth was achieved by: (1) synthesis of metre-sized single-crystal Cu(1 1 1) foil as substrate; (2) epitaxial growth of graphene islands on the Cu(1 1 1) surface; (3) seamless merging of such graphene islands into a graphene film with high single crystallinity and (4) the ultrafast growth of graphene film. These achievements were realized by a temperature-gradient-driven annealing technique to produce single-crystal Cu(1 1 1) from industrial polycrystalline Cu foil and the marvellous effects of a continuous oxygen supply from an adjacent oxide. The as-synthesized graphene film, with very few misoriented grains (if any), has a mobility up to ∼23,000 cm2 V−1 s−1 at 4 K and room temperature sheet resistance of ∼230 Ω/□. It is very likely that this approach can be scaled up to achieve exceptionally large and high-quality graphene films with single crystallinity, and thus realize various industrial-level applications at a low cost.