Flat boron by the numbers: Researchers calculate what it would take to make new 2-dimensional material

Jan 31, 2013
Two-dimensional sheets of boron that can be lifted off a substrate are possible to make via several theoretical methods suggested in a new paper by Rice University scientists. The material could be a useful complement to graphene and other 2-D materials for electronics, they said. Credit: Evgeni Penev/Rice University

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 Boris Yakobson, chuckling at the absurd image.

Yet something like that keeps happening to experimentalists working to grow two-dimensional . have a strong preference to clump into rather than assemble into pristine single-atom sheets, like carbon does when it becomes graphene. And boron clumps aren't nearly as sparkly.

Yakobson and his Rice colleagues have made progress toward 2-D boron through theoretical work that suggests the most practical ways to make the material and put it to work. Earlier calculations by the group indicated 2-D born would conduct electricity better than graphene.

Through first-principle calculations of the interaction of boron atoms with various substrates, the team came up with several possible paths experimentalists may take toward 2-D boron. Yakobson feels the work may point the way toward other useful two-dimensional materials.

The Rice team's results appear this week in the journal . Rice graduate student Yuanyue Liu and research scientist Evgeni Penev are co-authors of the paper.

Yakobson's lab first reported in a paper last year that unlike graphene, 2-D boron rolled into a nanotube would always be metallic. Also unlike graphene, the atomic arrangement can change without changing the nature of the material. Instead of the steady rank-and-file of in a perfect , 2-D boron consists of triangles. But boron could have vacancies – missing atoms – without affecting its properties.

That's the theory. The problem that remains is how to make the stuff.

"We are, perhaps, so close," Penev said. "Here we have conceived a material that resembles graphene, but is always conductive no matter what form it takes. What we're doing now is exploring different possibilities to connect our theories with reality."

The best method, they calculated, might be to feed boron into a furnace with silver or gold substrates in a process called chemical vapor deposition, commonly used to make graphene. The substrate is important, Penev said, because the atoms have to spill onto the surface and stick, but not too strongly.

"You have to have a substrate that doesn't want to dissolve boron," he said. "On the other hand, you want a substrate that doesn't bind too strongly. You should be able to detach the boron layer."

Then, like graphene, these atom-thick boron sheets could be applied to other surfaces for testing and, ultimately, for use in applications.

The study also calculated methods for creating sheets via saturation of boron atoms on the surface of boride substrates, and the evaporation of metal atoms from metal borides that leaves just the target atoms in a sheet.

"There are a lot of reasons boron could be interesting," said Liu, the paper's first author. "Boron is carbon's neighbor on the periodic table, with one less electron, which might bring in lots of new physics and chemistry, especially on the nanoscale. For example, 2-D boron is more conductive than graphene because of its unique electronic structure and .

"In fact, comparing (boron) with graphene is very helpful," he said. "The state-of-art synthesis methods for graphene provide us good templates to explore 2-D boron synthesis."

Yakobson is thinking a step beyond the current work. "There are many groups, at Rice and elsewhere, working on 2-D boron," he said. "To appreciate this work, you have to stand back and contrast it with graphene; in some sense, the synthesis of graphene is trivial.

"Why? Because graphene is a God-given material," he said. "It forms at the global minimum (energy) for – they go there willingly. But boron is a different story. It does not have a planar form as a global minimum, which makes it a really subtle problem. The novelty in this work is that we're trying to trick it into building a two-dimensional motif instead of three."

The search for 2-D materials with varying qualities is hot right now; another new paper from Rice on a hybrid graphene-hexagonal boron nitride shows the need for a 2-D semiconductor to complement the material's conducting and insulating elements.

Yakobson hopes his study serves as a guideline for practical routes to other novel materials. "Now that there is a growing interest in a variety of 2-D materials, this may be a template," he said.

Yakobson is Rice's Karl F. Hasselmann Professor of Mechanical Engineering and Materials Science and professor of chemistry.

Explore further: Researchers make major advances in dye sensitized solar cells

More information: onlinelibrary.wiley.com/doi/10.1002/anie.v52.5/issuetoc

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3 / 5 (2) Jan 31, 2013
You had me worried there for a moment. In theory of course.
I hope the gold does the trick.
1.6 / 5 (7) Jan 31, 2013
The flat boron could exist quite easily, the only problem is, how to prepare it, because it's complex like the quasicrystal. At the high temperatures - when such lattice may be formed - the distribution of boron atoms tends to achieve highest possible entropy and many other boron phases are formed. It's similar problem to preparation of high-temperature superconductors: the 1111010000101111 structure is way less probable than the symmetrical one 10101010101010101, because even within crystals the atoms are trying to occupy the lattice places in lowest possible ratios.
1.6 / 5 (7) Jan 31, 2013
Because graphene is a God-given material
The graphene is God-given material for researchers only (salary generator), as it promoted the explosion of theoretical publications. It's physical properties are way less suitable for the purposes of practical technology - which is why the physicists are seeking its replacements, after all. We should admit, that what is good for researchers may not be so good for the rest of people and vice-versa (cold fusion as an example: it's introduction would make many research programs obsolete immediately, so it's delayed obstinately).
2.1 / 5 (7) Jan 31, 2013
No. They got angry on cold fusion becaused it claimed to be something it is not. That's why they changed the name to Low Energy Nuclear Reactions, or LENR for short.
1 / 5 (4) Jan 31, 2013
They changed the name to LENR for to cover the twenty years standing ignorance of cold fusion research with mainstream physics. So that the laymans could say by now: "Well, the cold fusion was nonsense, and the mainstream physicists did well, when they denied it. But that LENR, this may be something - even NASA studies it!" It's just a part of mainstream propaganda - an inter-subjective attempt for resetting of history.

There's a bit of truth in the point, that the main portion of cold fusion reaction may be initiated with weak nuclear force instead of strong one. But in its consequences the mechanism, in which the small atom nuclei are fusing into larger ones plays no role at all - the coalesce of matter is still fusion, no matter which mechanism is initiated with, and the energy released is quite comparable to those generated with hot fusion (it's still the same conversion of matter into energy).
1 / 5 (6) Jan 31, 2013
Note that the founders of cold fusion never claimed, that the mechanism of cold fusion goes through strong nuclear force or some other mechanism. But the opponents of cold fusion insisted, that such mechanism would make the cold fusion infeasible and refused it as whole. But if cold fusion becomes feasible when the weak nuclear force is involved instead of strong one - why the cold fusion is still ignored - if not denied - with mainstream science?
Actually we can observe, the cold fusion is still denied and censored out with mainstream journals - with weak force or without it. The physicists in existing research of energy generation/conversion/transport and storage simply don't want any competition for their research from outside, as the acceptation of cold fusion reality would render them useless immediately. It's not just about fossil fuel lobby, but about biofuels, wind and solar plants, hydrogen energy research and/or batteries
1 / 5 (14) Jan 31, 2013
But Rossi has factories. He does.

I think what they really need is a muon catalyst.
2.9 / 5 (31) Jan 31, 2013
I think what Rossi really needs is a working shippable product.
3 / 5 (2) Feb 01, 2013
i think boeing modelled their dreamliner battery after rossi.
5 / 5 (2) Feb 01, 2013
Why are there SO many anti-science posters on a scientific news site? Depresses me.
1 / 5 (2) Feb 02, 2013
I just do want to have more money for scientific research - but the energetic and financial crisis resulting from long-term ignorance of cold fusion prohibits it. The physicists are trying to save their job places with ignorance of cold fusion at the personal level, but they will lose them anyway at the global level, because every ignorance comes with its own price.
5 / 5 (3) Feb 02, 2013
Why are there SO many anti-science posters on a scientific news site? Depresses me.

Fear. They live in a world they no longer understand (and which basically proves to them that their own world view is faulty with hard facts).

Either their mental capacity is inadequate or they have fallen so far behind that it's now easier to try and torpedo science than actually understand it.

But science can't be stopped. Stupid people can't stop smart people.
1 / 5 (3) Feb 02, 2013
I don't understand why people are so hung up on cold fusion. Yes room temperature energy is a big deal. But from today's technology point its not that important. We use electric grids to transfer energy and other technologies like batteries fill the gap quite nicely. One could even argue miniature LFTR Super Safe Nuclear reactors could even be used to run cars with one "tank" per life of the car. Please read http://rawcell.com (second proposed "We the People" Petition listed on the front page in order to get the technology the attention it needs. It needs 100,000 votes to get the white house to publicly acknowledge the technology which could change the future of energy production.
1.5 / 5 (17) Feb 02, 2013
I don't understand why people are so hung up on cold fusion. Yes room temperature energy is a big deal. But from today's technology point its not that important. We use electric grids to transfer energy and other technologies like batteries fill the gap quite nicely. One could even argue miniature LFTR Super Safe Nuclear reactors
It purports to be cheaper, more useful, more flexible, and much safer than all the current alternatives. It would be a HUGE deal.

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