Chemical vapour deposition can be used to grow graphene films on the metre scale. These films are, however, polycrystalline and have numerous grain boundaries, which can scatter charge carries and adversely affect the electronic properties of the films. Jiwoong Park and colleagues at Cornell University and Columbia University have now shown that overlap between crystallites in such polycrystalline graphene can be used to improve the conductivity of the films.
The researchers used dark-field transmission electron microscopy to map the location and shape of domains in polycrystalline graphene that had distinct lattice orientations. The material was imaged in a specifically designed electron microscopy chip and, after imaging, an area of interest was selected and electron-beam lithography used to pattern a field-effect transistor device around it. Electrical measurements could then be carried out on individual grain boundaries.
Park and colleagues examined grain boundaries created using different growth conditions and found that overlapping domains could increase conductivity by an order of magnitude. They also suggest that the electrical performance of polycrystalline graphene with the appropriate stitching between domains could rival that of graphene fabricated by exfoliating graphite.
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Beneficial boundaries. Nature Nanotech (2012). https://doi.org/10.1038/nnano.2012.121