Moiré patterns are spatial superstructures formed by overlaying two planar lattices. Observed for a long time as watered effects made by overlaying fine silk sheets, moiré patterns could appear at much lower length scales and can also be observed given the right tools. Graphene, the newly discovered Noble-prize worthy carbon-based material, assumes the role of the fine silk sheets at the atomic scale when supported on the surface of metals such as platinum, palladium, iridium, rhodium, etc. which exhibit different degrees of incommensurability (or lattice mismatch) between graphene and the metal. Graphene is promising for applications as a transparent conductor in low-power electronic devices, displays, and touch screens, and for this purpose, inexpensive and reproducible ways to grow highly-oriented, defect-free graphene sheets are desirable.
In an article recently published in ACS Nano, a team of researchers, led by Suneel Kodambaka, assistant professor of materials science and engineering, report the observation of moiré patterns of graphene even on a lattice-matched nickel surfaces and that graphene grows as a single crystal across facets of different orientations on nickel islands. These results suggest that single-crystalline graphene sheets can be grown even on polycrystalline substrates, an exciting result for the development of graphene-based technologies. The team included researchers from UCLA, Colorado School of Mines, and the University of Illinois.
This research was funded in part by the UCLA Henry Samueli School of Engineering and Applied Science, UC Discovery, and the Northrop Grumman Space Technology.
Related news and articles can be found at:
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Orientation-Dependent Work Function of Graphene on Pd(111), Applied Physics Letters 97, 143114 (2010)
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Virtual Journal of Nanoscale Science & Nanotechnology, October 11, 2010