When grown on silver, the two-dimensional form of boron known as borophene naturally forms corrugations, potentially making it suitable for use in stretchable, bendable electronics. Image: Zhuhua Zhang/Rice University.Though they're touted as ideal for electronics, two-dimensional materials like graphene may be too flat and difficult to stretch to serve in flexible, wearable devices. ‘Wavy’ borophene might be better, according to scientists at Rice University.
The Rice lab of theoretical physicist Boris Yakobson, together with experimental collaborators, has observed examples of naturally-undulating, metallic borophene, an atom-thick layer of boron. They suggest that transferring borophene onto an elastic surface would preserve the material's stretchability along with its useful electronic properties.
Highly-conductive graphene shows promise for use in flexible electronics, Yakobson said, but it is too stiff for devices that also need to stretch, compress or even twist. Whereas, as Yakobson and his colleagues have just discovered, borophene deposited on a silver substrate naturally develops nanoscale corrugations. As it is only weakly bound to the silver, this borophene could be moved to a flexible surface for use. This research appears in a paper in Nano Letters.
The Rice scientists collaborated with experimentalists at Argonne National Laboratory and Northwestern University to study borophene, which has been made in small quantities. Under the microscope, borophene displays corrugations that demonstrate its wavy nature, meaning it can be highly stretched once removed from the substrate, or reattached to a soft one, Yakobson said.
The Rice group builds computer simulations to analyze the properties of materials from the atoms up. Simulations by first author Zhuhua Zhang, a postdoctoral researcher in Yakobson's group, showed that hexagonal vacancies in borophene help soften the material to facilitate its corrugated form.
"Borophene is metallic in its typical state, with strong electron-phonon coupling to support possible superconductivity, and a rich band structure that contains Dirac cones, as in graphene," Yakobson said.
There is a hitch, however: borophene needs the underlying substrate to make it wavy; when grown on a featureless surface, its natural form is flat like graphene. According to Zhang, borophene is better seen as a triangular lattice with periodic arrays of hexagonal vacancies.
Borophene prefers to be flat because that's where its energy is lowest. Rather surprisingly, however, when grown on silver, borophene adopts its accordion-like form while silver reconstructs itself to match. The corrugation can then be retained by ‘re-gluing’ boron onto another substrate.
"This wavy conformation so far seems unique due to the exceptional structural flexibility and particular interactions of borophene with silver, and may be initially triggered by a slight compression in the layer when a bit too many boron atoms get onto the surface," Zhang said.
This story is adapted from material from Rice University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.