"In order to improve the properties of 2-D materials, it's important to first understand how they're put together at a fundamental scale," Idrobo said. "Our microscopy facility at ORNL allows us to see materials in a way they've never been seen before -- down to the level of individual atoms."
Yakobson, a theoretical physicist, and his team specialize in analyzing the interplay of energy at the atomic scale. With ORNL's images in hand, they were not only able to calculate the energies of a much more complex set of defects than are found in graphene or BN but could also match their numbers to the images.
Among the Yakobson team's interesting finds was the existence, reported last year, of conductive subnano "wires" along grain boundaries in MDS. According to their calculations, the effect only occurred when grains met at precise 60-degree angles. The ORNL electron microscopy images make it possible to view these grain boundaries directly.
The Rice researchers see many possible ways to combine the materials, not only in two-dimensional layers but also as three-dimensional stacks. "Natural crystals are made of structures bound by the van der Waals force, but they're all of the same composition," Lou said. "Now we have the opportunity to build 3-D crystals with different compositions."
"These are very different materials, with different electronic properties and band gaps. Putting one on top of the other would give us a new type of material that we call van der Waals solids," Ajayan said. "We could put them together in whatever stacking order we need, which would be an interesting new approach in materials science.
|Contact: Mike Williams|