• New transistor could cut 5% from world's

    From ScienceDaily@1:317/3 to All on Monday, April 11, 2022 22:30:36
    New transistor could cut 5% from world's digital energy budget
    Design also poised to save space, retain memory in event of power loss


    Date:
    April 11, 2022
    Source:
    University of Nebraska-Lincoln
    Summary:
    A new spin on one of the 20th century's smallest but grandest
    inventions, the transistor, could help feed the world's ever-growing
    appetite for digital memory while slicing up to 5% of the energy
    from its power-hungry diet.



    FULL STORY ==========================================================================
    A new spin on one of the 20th century's smallest but grandest inventions,
    the transistor, could help feed the world's ever-growing appetite for
    digital memory while slicing up to 5% of the energy from its power-hungry
    diet.


    ========================================================================== Following years of innovations from the University of Nebraska-Lincoln's Christian Binek and University at Buffalo's Jonathan Bird and Keke He,
    the physicists recently teamed up to craft the first magneto-electric transistor.

    Along with curbing the energy consumption of any microelectronics that incorporate it, the team's design could reduce the number of transistors
    needed to store certain data by as much as 75%, said Nebraska physicist
    Peter Dowben, leading to smaller devices. It could also lend those microelectronics steel- trap memory that remembers exactly where its
    users leave off, even after being shut down or abruptly losing power.

    "The implications of this most recent demonstration are profound," said
    Dowben, who co-authored a recent paper on the work that graced the cover
    of the journal Advanced Materials.

    Many millions of transistors line the surface of every modern integrated circuit, or microchip, which itself is manufactured in staggering numbers
    - - roughly 1 trillion in 2020 alone -- from the industry-favorite semiconducting material, silicon. By regulating the flow of electric
    current within a microchip, the tiny transistor effectively acts as
    a nanoscopic on-off switch that's essential to writing, reading and
    storing data as the 1s and 0s of digital technology.

    But silicon-based microchips are nearing their practical limits,
    Dowben said.

    Those limits have the semiconductor industry investigating and funding
    every promising alternative it can.



    ==========================================================================
    "The traditional integrated circuit is facing some serious problems,"
    said Dowben, Charles Bessey Professor of physics and astronomy at
    Nebraska. "There is a limit to how much smaller it can get. We're
    basically down to the range where we're talking about 25 or fewer
    silicon atoms wide. And you generate heat with every device on an
    (integrated circuit), so you can't any longer carry away enough heat
    to make everything work, either." That predicament looms even as the
    demand for digital memory, and the energy needed to accommodate it,
    have soared amid the widespread adoption of computers, servers and the internet. The microchip-enabled smartening of TVs, vehicles and other technology has only increased that demand.

    "We're getting to the point where we're going to approach the previous
    energy consumption of the United States just for memory (alone)," Dowben
    said. "And it doesn't stop.

    "So you need something that you can shrink smaller, if possible. But above
    all, you need something that works differently than a silicon transistor,
    so that you can drop the power consumption, a lot." 'Now that it works,
    the fun begins' Typical silicon-based transistors consist of multiple terminals. Two of them, called the source and drain, serve as the
    starting and end points for electrons flowing through a circuit. Above
    that channel sits another terminal, the gate.

    Applying voltage between the gate and source can dictate whether the
    electric current flows with low or high resistance, leading to either a
    buildup or absence of electron charges that gets encoded as a 1 or 0, respectively. But random-access memory -- the form that most computer applications rely on - - requires a constant supply of power just to
    maintain those binary states.



    ==========================================================================
    So rather than depend on electric charge as the basis of its approach,
    the team turned to spin: a magnetism-related property of electrons that
    points up or down and can be read, like electric charge can, as a 1 or
    0. The team knew that electrons flowing through graphene, an ultra-robust material just one atom thick, can maintain their initial spin orientations
    for relatively long distances -- an appealing property for demonstrating
    the potential of a spintronic-based transistor. Actually controlling
    the orientation of those spins, using substantially less power than a conventional transistor, was a much more challenging prospect.

    To do it, the researchers needed to underlay the graphene with the right material. Fortunately, Binek had already dedicated years to studying
    and modifying just such a material, chromium oxide. Crucially, chromium
    oxide is magneto-electric, meaning that the spins of the atoms at its
    surface can be flipped from up to down, or vice versa, by applying a
    meager amount of temporary, energy-sipping voltage.

    When applying positive voltage, the spins of the underlying chromium
    oxide point up, ultimately forcing the spin orientation of the graphene's electric current to veer left and yield a detectable signal in the
    process. Negative voltage instead flips the spins of the chromium oxide
    down, with the spin orientation of the graphene's current flipping to
    the right and generating a signal clearly distinguishable from the other.

    "Now you are starting to get really good fidelity (in the signal),
    because if you're sitting on one side of the device, and you've applied
    a voltage, then the current is going this way. You can say that's 'on,'"
    Dowben said. "But if it's telling the current to go the other way, that's clearly 'off.' "This potentially gives you huge fidelity at very little
    energy cost. All you did was apply voltage, and it flipped." As promising
    and functional as the team's demonstration was, Dowben said there exist
    plenty of alternatives to graphene that share its one-atom thickness but
    also boast properties better suited to a magneto-electric transistor. The
    race to overlay chromium oxide with those other 2D candidates is already
    on, he said, and marks "not the something, but the start of something."
    "Now that it works, the fun begins, because everybody's going to have
    their own favorite 2D material, and they're going to try it out," Dowben
    said. "Some of them will work a lot, lot better, and some won't. But
    now that you know it works, it's worth investing in those other, more sophisticated materials that could.

    "Now everybody can get into the game, figuring out how to make the
    transistor really good and competitive and, indeed, exceed silicon."
    The team received support from the National Science Foundation's
    Established Program to Stimulate Competitive Research, which funded the
    $20 million Emergent Quantum Materials and Technologies collaboration
    at Nebraska, and from the Semiconductor Research Corporation.


    ========================================================================== Story Source: Materials provided by
    University_of_Nebraska-Lincoln. Original written by Scott Schrage. Note: Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Keke He, Bilal Barut, Shenchu Yin, Michael D. Randle, Ripudaman
    Dixit,
    Nargess Arabchigavkani, Jubin Nathawat, Ather Mahmood,
    Will Echtenkamp, Christian Binek, Peter A. Dowben,
    Jonathan P. Bird. Graphene on Chromia: A System for
    Beyond‐Room‐Temperature Spintronics. Advanced Materials,
    2022; 34 (12): 2105023 DOI: 10.1002/adma.202105023 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/04/220411133508.htm

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