Strain-relief pattern formation in heteroepitaxy is well understood for particles with long-range attraction and is a routinely exploited organizational principle for atoms and molecules. However, for particles with short-range attraction such as colloids and nanoparticles, which form brittle assemblies, the mechanism(s) of strain-relief is not known. Here, we found that for colloids with short-range attraction, monolayer films on substrates with square symmetry could accommodate large compressive misfit strains through locally dewetted hexagonally ordered stripes. Unexpectedly, over a window of compressive strains, cooperative particle rearrangements first resulted in a periodic strain-relief pattern, which then guided the growth of laterally ordered defect-free colloidal crystals. Particle-resolved imaging of monomer dynamics on strained substrates also helped uncover cooperative kinetic pathways for surface transport. These processes, which substantially influenced the film morphology, have remained unobserved in atomic heteroepitaxy studies hitherto. Leaning on our findings, we developed a heteroepitaxy approach for fabricating hierarchically ordered surface structures.

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Extending atomic epitaxy concepts to colloidal systems for realizing functional surface structures has recently piqued scientific interest. Akin to the growth of ordered metal clusters on graphene moire, spatially ordered colloidal crystals have been realized on soft lithographically fabricated moirépatterns. In addition to moiréperiodicity, lattice misfit strain can bring about a further level of hierarchy in colloidal self-assembly, although its role in selforganization remains unexplored. Here, we demonstrate the self-organized growth of micrometer-sized colloidal pyramid arrays with lateral order extending over millimeter length scales on lattice-mismatched moirépatterns. By probing the film growth dynamics with singleparticle resolution, we uncovered the interplay between lattice misfit strain and topographically varying surface potential within the moiréunit cell, which significantly alters the nucleation process. We also show that the structural organization of colloids within moiréregions primarily depends on the moiréangle, and by tuning it, multiple levels of hierarchy can be achieved.

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