Connecting quantum dots into epitaxially connected superlattices is a new and exciting route to novel two-dimensional materials. The ability to control the atomic structure of the quantum dot building block (<i>i.e.,</i> size, shape and composition) and the geometry of the superstructure creates fertile opportunity space to synthesize and study new classes of 2D materials. Theoretical calculations on these systems predict interesting phenomena including topological states and Dirac cones. We present recent advances in our group to fabricate atomically connected quantum dot superlattices with structural coherence approaching a single atomic bond length.<br/>Despite the high degree of structural coherence, surprisingly charge carriers are strongly localized, as shown by the first charge transport measurement in an atomically coherent quantum dot device. Before theoretically predicted properties can be probed, outstanding knowledge gaps concerning the formation of epitaxially connected superlattices need to be resolved. The formation of superlattice polymorphs (e.g., square or honeycomb lattices) is related to the preferred orientation of constituent nanocrystal building blocks and the rate of assembly. Understanding and ultimately controlling the transformation of the nanocrystal assembly into an atomically coherent superlattices hinges on establishing deeper insights into the fundamental transformation mechanism and the complex interplay of transport and reaction dynamics of the chemical trigger near the nanocrystal surface. We discuss recent efforts in our group to disentangle these effects. To better understand how polydispersity of the quantum dot building blocks impacts long-range order in the 2D assembly, we developed analytical methods to quantitatively characterize the propagating disorder in terms of a paracrystal model; this approach underscores the dramatic impact of angstrom scale translational disorder on structural correlations at hundreds of nanometers.

Epitaxially connected quantum dot superlattices

253rd National Meeting (2017)

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