Category Archives: 2D materials

Bending 2D nanomaterial could ‘switch on’ future technologies

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Rice University scientists find new workable feature of a class of 2D materials

Rice University materials scientist Boris Yakobson and collaborators uncovered a property of ferroelectric 2D materials that could be exploited as a feature in future devices.

Because they bend in response to an electrical stimulus, single-layer ferroelectric materials can be controlled to act as a nanoscale switch or even a motor, according to the study published in ACS Nano.

Polarization drives the larger atoms to one side of the 2D-material layer and the smaller atoms to the other side. This asymmetrical distribution of the atoms or ions causes the material surface to bend in ferroelectric state.

The study looked at 2D indium phosphide (InP) as a representative of the class of ferroelectrics for which it predicts this property.

“This new property or flexing behavior has to be tested in a laboratory for specific substances,” Yakobson said. “Its most likely use will be as a type of switch. This behavior is very fast, very sensitive, which means that with a very tiny local signal you can maybe switch on a turbine or electrical engine, or control adaptive-optics telescopes’ mirrors. That’s basically the essence of these actuators.”

–  See more at Rice News

A crystal shape conundrum is finally solved

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Rice theorists’ method can predict shapes of crystals that lack symmetry

A crystal’s shape is determined by its inherent chemistry, a characteristic that ultimately determines its final form from the most basic of details. But sometimes the lack of symmetry in a crystal makes the surface energies of its facets unknowable, confounding any theoretical prediction of its shape.

Theorists at Rice University say they’ve found a way around this conundrum by assigning arbitrary latent energies to its surfaces or, in the case of two-dimensional materials, its edges.

Yes, it seems like cheating, but in the same way a magician finds a select card in a deck by narrowing the possibilities, a little algebraic sleight-of-hand goes a long way to solve the problem of predicting a crystal’s shape.

The method described in Nature Computational Science shows using what they call auxiliary edge energies can bring predictions back in line with the Wulff construction, a geometrical recipe in use for more than a century to determine how crystals arrive at their final equilibrium shapes.

–  See more at Rice News

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Bumps could smooth quantum investigations

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Rice University models show unique properties of 2D materials stressed by A new theory by Rice University researchers suggests that 2D materials like hexagonal boron nitride, at top, could be placed atop a contoured surface, center, and thus be manipulated to form 1D bands that take on electronic or magnetic properties. Courtesy of the Yakobson Research Groupcontoured substrates

Atoms do weird things when forced out of their comfort zones. Rice University engineers have thought up a new way to give them a nudge.

Materials theorist Boris Yakobson and his team at Rice’s George R. Brown School of Engineering have a theory that changing the contour of a layer of 2D material, thus changing the relationships between its atoms, might be simpler to do than previously thought.

While others twist 2D bilayers — two layers stacked together — of graphene and the like to change their topology, the Rice researchers suggest through computational models that growing or stamping single-layer 2D materials on a carefully designed undulating surface would achieve “an unprecedented level of control” over their magnetic and electronic properties.

They say the discovery opens a path to explore many-body effects, the interactions between multiple microscopic particles, including quantum systems.

The paper by Yakobson and two alumni, co-lead author Sunny Gupta and Henry Yu, of his lab appears in Nature Communications.

– See more at Rice News

Nickel’s need for speed makes unusual nanoribbons

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Rice lab studies mechanism behind bilayer molybdenum disulfide ribbons

It’s now possible to quickly make ultrathin nanoribbons of molybdenum disulfide, with a speedy nickel nanoparticle leading the way.Materials theorist Boris Yakobson and his team at Rice University’s George R. Brown School of Engineering collaborated with the Honda Research Institute and others to make tightly controlled bilayer nanoribbons of the material commonly known as MoS2, a step forward with potential applications in quantum computing.

Honda, with scientists at Rice, Columbia University and Oak Ridge National Laboratory, found that nanoparticles of nickel exposed to molybdenum oxide and sodium bromide powders and sulfur gas in a chemical vapor deposition furnace wrangle the resulting nanoribbons into shape, constraining their width to several micrometers. At the same time, the nickel catalyzes a thinner second layer of less than 30 nanometers, roughly equivalent to the width of the nanoparticle itself.

The study appears in Science Advances.

– See more at Rice News

Weak bonds a strength in making borophene

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Rice theory shows potential to synthesize material on an insulator

Borophene may be done tantalizing materials scientists and start serving their ambitions, if a new approach by Rice University researchers can be turned into practice.

Materials theorist Boris Yakobson of Rice’s George R. Brown School of Engineering and his group suggest a method to synthesize borophene, the 2D version of boron, in a way that could make it easier to free up or manipulate.

According to the group’s paper in the American Chemical Society journal ACS Nano, that would involve growing the exotic material on hexagonal boron nitride (hBN), an insulator, rather than the more traditional metallic surfaces typically used in molecular beam epitaxy (MBE).

The Yakobson team, including lead author and graduate student Qiyuan Ruan and co-authors Luqing Wang, a Rice alumnus, and research scientist Ksenia Bets, calculated the atom-level energies of borophene and hBN. They found the step-and-plateau hBN substrate encouraged boron atoms floating in the MBE chamber to alight, nucleating growth.

– See more at Rice News