Nanostructure Formation in a Vapor Phase Using Heterogeneous Nucleation Sites

The vapor phase formation of nanostructures through self-assembly, directed-assembly or island growth modes has been studied for many years and has yielded a wide array of nanostructures. We, however, have devised a simple technique whereby periodic arrays of nanostructures are first formed using dynamic templating and are then treated as heterogeneous nucleation sites in subsequent assembly processes. In a typical processes, Au nanostructures are confined between an oxide substrate and a second material from which adatoms can be sourced through sublimation. At the assembly temperature these adatoms are unable to spontaneously form stable clusters on the substrate surface. When they encounter a Au template, however, they are readily incorporated to form a new nanostructure with its own unique properties. This strategy has been demonstrated for scenarios where Au in transformed into an alloy, where it forms a eutectic liquid which upon cooling phase separates into a heterodimer structure, where the Au template is sacrificed and replaced with a Wulff-shaped Pd nanostructure and where Wulff-shaped Au nanostructures are transformed into triangular AuAg nanoprisms.

Schematic of the growth mode devised to form periodic arrays of AuAg nanoprisms.

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SEM images of arrays of Au templates and AgAu triangles (top) and AgGe heterodimers and Ag nanocrescents (bottom).