Beyond 2D Materials: Layered Crystals with a Twist
|Date/Time:||Thursday, 31 Oct 2019 from 4:10 pm to 5:00 pm|
|Channel:||Condensed Matter Physics|
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Two-dimensional (2D) materials such as graphene, hexagonal boron nitride, and a family of transition metal dichalcogenides have attracted significant interest due to novel properties that arise in atomically thin crystals. Much less explored are layered van der Waals crystals and heterostructures that, assembled from 2D building blocks, lie between the single-layer and bulk limits. In the bottom-up synthesis of such van der Waals materials, phenomena such as spontaneous phase separation, transformations between different crystal polymorphs, hybrid dimensionality, and introduction of defects provide
unprecedented opportunities for controlling morphology, interface formation, and novel degrees of freedom such as interlayer twist. But going beyond a single layer also poses extraordinary challenges, both due to the diversity and complexity of the possible few-layer structures and the difficulty of probing functionality, such as optoelectronics, at the
relevant length scales.
Here, I discuss recent research that addresses these challenges by combining in-situ microscopy of synthesis and processing with advanced materials characterization and optoelectronic measurements at the ultimate resolution limit. The materials focus is on group IVA (Ge, Sn) chalcogenides, a relatively unexplored class of layered crystals with multiple stable polymorphs of different chalcogen content. Our results illustrate the rich sets of materials architectures and functionalities that can be realized in van der Waals crystals beyond the 2D limit.