期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2016
卷号：113
期号：43
页码：12094-12098
DOI：10.1073/pnas.1608568113
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The monomer surface mobility is the single most important parameter that decides the nucleation density and morphology of islands during thin-film growth. During template-assisted surface growth in particular, low surface mobilities can prevent monomers from reaching target sites and this results in a partial to complete loss of nucleation control. Whereas in atomic systems a broad range of surface mobilities can be readily accessed, for colloids, owing to their large size, this window is substantially narrow and therefore imposes severe restrictions in extending template-assisted growth techniques to steer their self-assembly. Here, we circumvented this fundamental limitation by designing templates with spatially varying feature sizes, in this case moiré patterns, which in the presence of short-range depletion attraction presented surface energy gradients for the diffusing colloids. The templates serve a dual purpose: first, directing the particles to target sites by enhancing their surface mean-free paths and second, dictating the size and symmetry of the growing crystallites. Using optical microscopy, we directly followed the nucleation and growth kinetics of colloidal islands on these surfaces at the single-particle level. We demonstrate nucleation control, with high fidelity, in a regime that has remained unaccessed in theoretical, numerical, and experimental studies on atoms and molecules as well. Our findings pave the way for fabricating nontrivial surface architectures composed of complex colloids and nanoparticles as well.
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