Block copolymer templated patterning of silicon surfaces and their applications

The use of self-assembled polymer structures to direct the formation of mesoscopic (1-100 nm) features on silicon could provide a fabrication-compatible means to produce nanoscale patterns on silicon, supplementing conventional lithographic techniques. In the beginning of this thesis, we demonstrate nanoscale etching of silicon, using standard aqueous-based fluoride etchants, to produce three dimensional nanoscale features. The amphiphilic block copolymers, polystyrene- block-poly(4-vinyl pyridine), denoted as PS-b-P4VP with different molecular weights, serve to direct the silicon surface chemistry by controlling the spatial location of the reaction, as well as concentration of reagents. Controllable shapes, sizes, average spacing, and chemical functionalities of the patterned nanostructures are obtained through the modulation of the experimental conditions, such as crystallographic orientation of the used silicon wafer, concentration of the etchant, etching time, et al. This etching method is not limited exclusively to flat surfaces: patterning on curved surfaces through the same etching recipe is also demonstrated in the thesis.;As one of many possibilities, we also demonstrate in this thesis the fabrication of ordered arrays of gold nanoparticle aggregations on this nanopatterned surface. The interiors of etch pits are functionalized with an alpha,o-mercaptoalkene to "capture" gold colloids into the etch pits. Due to the spatial restriction of the etch pits, controlled aggregation behaviours were achieved for nanoparticles of different sizes. The nanoparticle arrays display aggregation-dependent surface enhanced Raman scattering effects. The nanoparticle arrays with controllable aggregations are expected to be useful for trace biological and chemical analysis.;One unique feature of the patterned silicon surface is that the interiors of etch pits are hydride terminated, while the exteriors of the etched structures remain covered by the native oxide. The interiors of the resulting etch pits can be selectively functionalized with organic monolayers, metal nanoparticles, and other materials, leading to ordered arrays on silicon. In the second part of this thesis, we demonstrate the construction of metal nanoparticle arrays with a controlled spatial distribution on surfaces, utilizing both galvanic displacement and hydrosilylation reactions on hydride-terminated silicon surfaces by taking advantage of the distinct functionalities between the etch pit interior and the flat top surface, hydride versus oxide.