Boasting the conductivity, strength and flexibility we wished for, graphene was proposed as one of the most likely substitutes for silicon and other materials. Its launch into the market however is still slow. What is curbing graphene from industrial applications? One factor is that top quality single-crystal graphene produced so far is just a couple of millimeters or maximum centimeters in size. Recently, a team led by Prof. Feng Ding and Prof. Rodney Ruoff at the Center for Multidimensional Carbon Materials within the Institute for Basic Science (IBS), Prof. Kaihui Liu at Peking University, and their collaborators reported the synthesis of a large sheet of monolayer single-crystal graphene. This result allows a leap forward in graphene production: advancing from a technique that synthesizes a few ? sheet of single-crystal graphene in a couple of hours, to an optimized method that allows the creation of an almost-perfect (> 99.9 % aligned) 5 × 50 ? single-crystal graphene in just 20 minutes. Moreover, the low production costs, comparable to commercially available lower quality polycrystalline graphene films, could expand its usability. Detailed in Science Bulletin, 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 honeycomb-shaped monolayer of carbon atoms, uniform throughout the whole material, offers its exceptional properties to single-crystal graphene. On the other hand, polycrystalline graphene is formed by randomly oriented graphene islands, which decrease its quality. Currently, scientists are able to grow meter-sized polycrystalline graphene and smaller single-crystal graphene, ranging from 0.01 mm2 to a few ?. The synthesis of large single-crystal graphene at a low cost has been considered a critical goal of graphene synthesis.
In this study, graphene is grown on the surface of a 5 × 50 ? copper foil, which was transformed into a single-crystal copper foil by heating to ~ 1,030?. A temperature slope from hot to cold moved the so-called grain boundary onwards, creating a perfect single-crystal. In the heating and cooling treatment, copper atoms migrate inside the material, arranging into an ordered structure with fewer defects. “The secret to obtain single-crystal graphene of very large size, is to have a perfect single crystal copper as a base to start with. Large single-crystal copper foil is not available in the market, so labs must build it with their own means,” explains Feng Ding, group leader at the Center for Multidimensional Carbon Materials.
The full story is available below.
Source: Science Daily