Borophene

The atomic structure is a consequence of an interplay between two-center and multi-center in-plane bonding, which is typical for electron deficient elements like boron.

In terms of mechanical properties, v1/6 (where the fraction denotes the hollow hexagon density) borophene is theoretically predicted to have an in-plane modulus of up to 210 N/m, Poisson's ratio of up to 0.17.

These predicted properties are partially supported by experimental work, where v1/6 borophene was synthesized on a surface reconstructed Ag(111) substrate.

[9] Ideal flexible electronics require the ability to be stressed, compressed, and even twisted into a wide array of geometries; however, most 2D materials reported to date are unable to meet all of these criteria since they are stiff against in-plane deformation.

[9] Comparing these values to graphene, the prototypical 2D material, the modulus and bending stiffness of borophene is lower while the Poisson's ratio is similar.

[7][8] Borophene also has potential as an anode material for batteries due to high theoretical specific capacities, electronic conductivity, and ion transport properties.

[5] Computational studies by I. Boustani and A. Quandt showed that small boron clusters do not adopt icosahedral geometries like boranes, instead they turn out to be quasi-planar (see Figure 2).

[12][13][14] Additional studies showed that extended, triangular borophene (Figure 1(c)) is metallic and adopts a non-planar, buckled geometry.

[22][23][24] In particular, the lattice structure of borophene was shown to depend on the metal surface, displaying a disconnect from that in a freestanding state.

Utilizing diborane (B2H6) pyrolysis as a pure boron source, a group of researchers reported the growth of atomic-thickness borophene sheets via chemical vapor deposition (CVD) for the first time.

[28] Atomic-scale characterization, supported by theoretical calculations, revealed structures reminiscent of fused boron clusters consisting of mixed triangular and hexagonal motives, as previously predicted by theory and shown in Figure 1.