Scanning electron microscope image of large 100 µm synthetic graphene domains grown by CVD on a copper catalyst.
The electronic, chemical, magnetic and mechanical properties of graphene have been shown to be simply outstanding. In order to unlock graphene’s potential impact in applications at the industrial level new ways of scalable manufacturing of graphene must be sought. One leading new approach is the bottom-up growth of large area films of synthetic graphene using a technique known as Chemical Vapour Deposition (CVD) with cheap metals such as copper used as the catalyst. This approach builds upon the concepts developed for carbon nanotubes and diamond CVD growth. In the same way that the innovation in growing single crystals of silicon revolutionized the electronics and technology industry, it is possible that the same may happen with synthetic graphene. Leading research groups can now grow single crystals of pure defect-free monolayer graphene approaching 1mm in size and polycrystalline continuous films greater than 750 cm using CVD.
A key factor in obtaining outstanding properties of graphene is that its atomic structure is in pristine order. Transmission electron microscopy (TEM) is an ideal way of directly imaging the atomic structure of graphene to detect defects, impurities, cracks and holes in the sample.
However, obtaining contrast from a material that is only one atom thick and made from a light element such as carbon is very challenging. TEM requires high energy electrons to pass through the sample to obtain an image and these electrons often damage the graphene and make it hard to see the true atomic structure. However, significant innovation has occurred in the design of electron microscopes so they can operate with electrons with lower energy and not damage graphene. The Department of Materials at the University of Oxford has a world-leading TEM and my group has developed innovative ways of preparing graphene samples specifically for TEM analysis. We can now directly image individual carbon atoms in graphene and identify any deviations from the pristine structure that could be detrimental to the performance of their graphene in applications.
With technology, such as touch screens, already produced with synthetic graphene, it seems that the major challenge is optimizing the materials production and processing at a scale needed for industrial development.
Dr Jamie Warner is a University Research Fellow at the Department of Materials, University of Oxford. His work is on engineering carbon nanomaterials using controlled electron beam irradiation.