Rice researchers find subtle interactions with substrate may lead to better control
Graphene islands formed in two distinctly different shapes on separate grains of copper (colored in blue and red) grown simultaneously because the substrates' atomic lattices have different orientations, according to Rice University researchers. Image by Y. Hao/coloring by V. Artyukhov
What lies beneath growing islands of graphene is important to its properties, according to a new study led by Rice University.
Scientists at Rice analyzed patterns of graphene – a single-atom-thick sheet of carbon – grown in a furnace via chemical vapor deposition. They discovered that the geometric relationship between graphene and the substrate, the underlying material on which carbon assembles atom by atom, determines how the island shapes emerge. The study led by Rice theoretical physicist Boris Yakobson and postdoctoral researcher Vasilii Artyukhov shows how the crystalline arrangement of atoms in substrates commonly used in graphene growth, such as nickel or copper, controls how islands form. The results appear this week in Physical Review Letters.
- See more at: Rice News
A recent work from the group on atomistic modeling of carbon fibers appears in the quarterly Editor’s Highlights for Carbon. These articles are handpicked by the Editors for the reader community and are made freely available for a limited time.
Carbon fiber structure is excessively complex and modeling attempts necessarily rely on various approximations. We have designed structural faults with atomistic details, pertaining to polyacrylonitrile (PAN) derived fibers, and probed them using large-scale molecular dynamics simulations to uncover trends and gain insight into the effect of local structure on the strength of the basic structural units (BSUs) and the role of interfaces between regions with different degrees of graphitization. Besides capturing the expected strength degrading with increasing misalignment, the designed basic structural units reveal atomistic details of local structural failure upon tensile loading.
The image shows an atomistic representation of a BSU (~ 40,000 atoms); for clarity part of the geometry is not rendered. A misoriented block is highlighted. Load is applied along the fiber axis, as indicated by the thick arrow, by displacing thin slabs (“handles”) at the top and bottom of the system, schematically represented as plates.
Rice University theory shows it should be possible to tune material’s properties
Graphene nanoribbons can be enticed to form favorable "reconstructed" edges by pulling them apart with the right force and at the right temperature, according to researchers at Rice University. The illustration shows the crack at the edge that begins the formation of five- and seven-atom pair under the right conditions. Illustration by ZiAng Zhang
Theoretical physicists at Rice University are living on the edge as they study the astounding properties of graphene. In a new study, they figure out how researchers can fracture graphene nanoribbons to get the edges they need for applications.
New research by Rice physicist Boris Yakobson and his colleagues shows it should be possible to control the edge properties of graphene nanoribbons by controlling the conditions under which the nanoribbons are pulled apart.
In the work, which appeared this month in the Royal Society of Chemistry journal Nanoscale, the Rice team used sophisticated computer modeling to show it’s possible to rip nanoribbons and get graphene with either pristine zigzag edges or what are called reconstructed zigzags.
- See more at: Rice News
The January 21 issue of Adv. Funct. Mater. features on its back cover work on graphene grain boundaries
The image shows a simulated grain boundary stitching two graphene domains tilted at a 28° angle exhibits a well-defined sinuous shape, which is revealed to be energetically preferred. Such sinuous grain boundary, appeared to be a curved river on land, are highlighted by B. I. Yakobson and co-workers on page 367 as a new channel to explore novel electronic behavior in graphene and to reach the as yet unexplored flatlands of two-dimensional materials.
2015 CASC Brochure features work from the group
Images illustrating two works from the group are featured in the 2015 Brochure published by the Coalition for Academic Scientific Computation - an alliance of 79 of America’s most forward thinking research universities, national labs and computing centers, including Rice’s Ken Kennedy Institute for Information Technology. On page 2, the highlight box “Something new under the sun” shows a collage based on a recent Nanoscale paper, and our extensive sampling of the CNT end-caps energy landscape, published in ACS Nano, is featured in the top box on page 3.
Nano Letters features our work on the cover of its December 2014 issue
In a recent Nano Lett. article, we demonstrate that a 2D mono-elemental semiconductor is a promising candidate. This is exemplified by first-principles study of 2D phosphorus (P), a recently fabricated high-mobility semiconductor. Most of the defects, including intrinsic point defects and grain boundaries, are electronically inactive, thanks to the homoelemental bonding, which is not preferred in heteroelemental system such as MX2. Unlike MX2, the edges of which create deep gap states and cannot be eliminated by passivation, the edge states of 2D P can be removed from the band gap by hydrogen termination. We further find that both the type and the concentration of charge carriers in 2D P can be tuned by doping with foreign atoms.
The cover image represents a “phosphorescent” rendering of some structural and electronic signatures of 2D phosphorus arranged in a collage inspired by the digital rain from “The Matrix” movie.
See more at: Rice News: Phosphorus ‘rain’
Rice University theorists determine factors that give tubes their chiral angles
Many a great idea springs from talks over a cup of coffee. But it’s rare and wonderful when a revelation comes from the cup itself.
Rice University theoretical physicist Boris Yakobson, acting upon sudden inspiration at a meeting last year in Arlington, Va., obtained a couple of spare coffee cups from a server and a pair of scissors and proceeded to lay out – science fair-style – an idea that could have far-reaching implications for the nanotechnology industry.
As reflected in a new paper in Nature Communications, Yakobson and his Rice colleagues, postdoctoral researcher Vasilii Artyukhov and research scientist Evgeni Penev, had come up with the seed (or perhaps, bean) of a simple formula that describes why nanotubes have chirality. Chirality is the property that describes the angle of the carbon atom hexagons that make up a nanotube’s walls.
- See more at: Rice News
Rice University physicists find 2-D form pays no heed to defects
Defects damage the ideal properties of many two-dimensional materials, like carbon-based graphene. Phosphorus just shrugs.
That makes it a promising candidate for nano-electronic applications that require stable properties, according to new research by Rice University theoretical physicist Boris Yakobson and his colleagues.
In a paper in the American Chemical Society journal Nano Letters, the Rice team analyzed the properties of elemental bonds between semiconducting phosphorus atoms in 2-D sheets. Two-dimensional phosphorus is not theoretical; it was recently created through exfoliation from black phosphorus.
- See more at: Rice News
Rice University calculations show carbon-atom chain would go metal to semiconductor
Applying just the right amount of tension to a chain of carbon atoms can turn it from a metallic conductor to an insulator, according to Rice University scientists.
Stretching the material known as carbyne — a hard-to-make, one-dimensional chain of carbon atoms — by just 3 percent can begin to change its properties in ways that engineers might find useful for mechanically activated nanoscale electronics and optics.
The finding by Rice theoretical physicist Boris Yakobson and his colleagues appears in the American Chemical Society journal Nano Letters.
- See more at: Rice News
Rice study narrows the possibilities for gaining control of nanotube type
A single-walled carbon nanotube grows from the round cap down, so it’s logical to think the cap’s formation determines what follows. But according to researchers at Rice University, that’s not entirely so.
Theoretical physicist Boris Yakobson and his Rice colleagues found through exhaustive analysis that those who wish to control the chirality of nanotubes – the characteristic that determines their electrical properties – would be wise to look at other aspects of their growth.
In the study by Yakobson, research scientist Evgeni Penev and postdoctoral researcher Vasilli Artyukhov that was published recently by the American Chemical Society journal ACS Nano, the Rice researchers found that the elastic energy landscapes involved in cap formation are not strong enough to dictate the nanotube’s chirality….more
Check out our posters at the Department of Materials Science and NanoEngineering Open House, Mon., December 9, 2013, Duncan Hall:
- Computational Materials unCovered
- Predictive theory of nanocarbon growth: doping, defects, chirality
- Computational nanomechanics of 3D carbon architectures
Rice University researchers calculate what it would take to make new two-dimensional material
It would be a terrible thing if laboratories striving to grow graphene from carbon atoms kept winding up with big pesky diamonds.
“That would be trouble, cleaning out the diamonds so you could do some real work,” said Rice University theoretical physicist Boris Yakobson, chuckling at the absurd image.
Yet something like that keeps happening to experimentalists working to grow two-dimensional boron. Boron atoms have a strong preference to clump into three-dimensional shapes rather than assemble into pristine single-atom sheets, like carbon does when it becomes graphene. And boron clumps aren’t nearly as sparkly…more
High-impact journal publishes centennial edition with broad overview of materials science at Rice
Materials scientists who received Volume 24, Issue 36 of the respected journal Advanced Materials recently may have noticed it contained Rice University research and nothing else.
That is no mistake. The journal published a special issue this fall focused on Rice, the home of a large number of materials researchers that has been recognized by a Times Higher Education survey as the best in the world. more…
Like tiny ships finding port in a storm, carbon atoms dock with the greater island of graphene in a predictable manner. But until recent research by scientists at Rice University, nobody had the tools to make that kind of prediction.