Paper NS2-TuA1
Size-selective Templated Self-Assembly of Particles

Tuesday, November 10, 2009, 2:00 pm, Room L

The special properties of nanoscale objects, such as metal and semiconductor nanoparticles, nanowires, or nanotubes, make them promising building blocks of novel optical and electronic devices. The systematic fabrication of devices usually requires the integration of these heterogeneous materials into a larger, ordered structure. More complex device architectures may, in addition, entail the selective assembly of several different types of small objects into pre-defined locations or demand an assembly with the correct orientation when such objects are nonspherical.

Serial pick-and-place techniques are no longer economical at these length scales. Self-assembly mechanisms can arrange a large number of objects in parallel, but will mainly produce homogeneous monolayers limited to the characteristic length-scale of the assembled objects (e.g. the diameter of the particles). Templated assembly on the other hand, provides an adequate strategy for the massively parallel arrangement of particles into designed patterns of arbitrary structure. With selective assembly sites, integration of different components becomes feasible.

Here we show concepts and experimental implementations for the selective templated self-assembly of spherical particles of different size. Particles between 200 and 500 nm in size are assembled selectively into predetermined locations on a template. We use capillary assembly from aqueous suspensions onto templates with topographic features that are selective for a certain particle size. The templates are prepared in poly(dimethylsiloxane) (PDMS) molded from a topographically patterned master. The master is a Si wafer patterned by electron beam lithography.