• Don't underestimate undulating graphene

    From ScienceDaily@1:317/3 to All on Wed Mar 23 22:30:44 2022
    Don't underestimate undulating graphene
    Unique electronics made possible by wavy patterns that channel electrons


    Date:
    March 23, 2022
    Source:
    Rice University
    Summary:
    A theory suggests putting graphene on an undulating surface stresses
    it enough to create a minute electromagnetic field. The phenomenon
    could be useful for creating 2D electron optics or valleytronics
    devices.



    FULL STORY ==========================================================================
    Lay some graphene down on a wavy surface, and you'll get a guide to one possible future of two-dimensional electronics.


    ==========================================================================
    Rice University scientists put forth the idea that growing atom-thick
    graphene on a gently textured surface creates peaks and valleys in the
    sheets that turn them into "pseudo-electromagnetic" devices.

    The channels create their own minute but detectable magnetic
    fields. According to a study by materials theorist Boris Yakobson,
    alumnus Henry Yu and research scientist Alex Kutana at Rice's George
    R. Brown School of Engineering, these could facilitate nanoscale optical devices like converging lenses or collimators.

    Their study appears in the American Chemical Society's Nano Letters.

    They also promise a way to achieve a Hall effect -- a voltage difference
    across the strongly conducting graphene -- that could facilitate
    valleytronics applications that manipulate how electrons are trapped in "valleys" in an electronic band structure.

    Valleytronics are related to spintronics, in which a device's memory bits
    are defined by an electron's quantum spin state. But in valleytronics, electrons have degrees of freedom in the multiple momentum states (or
    valleys) they occupy. These can also be read as bits.

    This is all possible because graphene, while it may be one of the
    strongest known structures, is pliable enough as it adheres to a surface
    during chemical vapor deposition.

    "Substrate sculpting imparts deformation, which in turn alters
    the material electronic structure and changes its optical response
    or electric conductivity," said Yu, now a postdoctoral researcher at
    Lawrence Livermore National Laboratory. "For sharper substrate features
    beyond the pliability of the material, one can engineer defect placements
    in the materials, which creates even more drastic changes in material properties." Yakobson compared the process to depositing a sheet of
    graphene on an egg crate. The bumps in the crate deform the graphene,
    stressing it in a way that creates an electromagnetic field even without electrical or magnetic input.

    "The endless designs of substrate shapes allow for countless optical
    devices that can be created, making possible 2D electron optics,"
    Yakobson said. "This technology is a precise and efficient way of
    transmitting material carriers in 2D electronic devices, compared to traditional methods." Yakobson is the Karl F. Hasselmann Professor of Materials Science and NanoEngineering and a professor of chemistry.

    The Office of Naval Research (N00014-18-1-2182) and the Army Research
    Office (W911NF-16-1-0255) supported the research.


    ========================================================================== Story Source: Materials provided by Rice_University. Original written
    by Mike Williams. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Henry Yu, Alex Kutana, Boris I. Yakobson. Electron Optics and
    Valley Hall
    Effect of Undulated Graphene. Nano Letters, 2022; DOI: 10.1021/
    acs.nanolett.2c00103 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220323114513.htm

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