Nano Lett. 16, 6622–6627 (2016)

Stretchability and conductivity rarely go hand in hand in the same material and finding exceptions to this rule remains a challenge. Two-dimensional materials offer a wide range of electronic properties, notably graphene, a conductor with outstanding transport properties. Being atomically thin, 2D materials are highly bendable, but their limited ability to sustain in-plane deformations precludes their immediate incorporation into flexible devices.

Boris Yakobson, Mark Hersam, Nathan Guisinger and colleagues at Northwestern University, Argonne National Laboratory and Rice University now report on a new class of highly stretchable and compressible 2D sheets of boron, or borophenes. At elevated growth temperatures, borophene, epitaxially deposited on a Ag(111) substrate, adopts an unusual corrugated structure. Steps on the Ag substrate surface act as nucleation centres resulting in the formation of the undulating pattern of the borophene. Theoretical analysis shows that the observed borophene phase with periodic nanoscale waves is energetically favourable. The wavy borophene sheet exhibits record small bending stiffness while its metallicity remains well preserved, which potentially makes borophene an alternative to flat and stiff graphene. The researchers suggest that the undulated borophene could be successfully separated from the Ag(111) substrate and subsequently transferred onto elastomeric substrates without compromising its electronic properties and keeping the periodic buckling intact.