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Soft nanoscale epitaxy

Researchers in the Irvine and Talapin groups at the University of Chicago MRSEC used nanoparticle membranes discovered by the Jaeger and Lin groups to develop a platform for studies of homo= and heteroepitaxy in nanocrystal assemblies.  Their work revealed exceptional strain tolerance of epitaxial growth in nanocrystal-based materials.  To demonstrate this effect, they used a periodically curved substrate with local variations of lattice spacing, formed by "draping" a monolayer of 8.8 nm PbS nanocrystals over a layer of 230nm polystyrene beads (left). 

The structure of the nanocrystal monolayer revealed a complex curvature and strain distribution, but the epitaxial growth when using 8.3nm Au nanocrystals resulted in the formation of a spatially patterned adlayer at submonolayer coverage (middle) and uniform adlayer at near-monolayer coverage (right), similar to that observed on a flat nanocrystal substrate.  The inset in the right panel shows the bond angle plot for the epitaxial nanocrystal adlayer.