From Nanowires to Nanopores: A Versatile Method for Electroless Deposition of Nanostructures on Micropatterned Organic Substrates.

We demonstrate a fast, flexible, parallel, and highly controllable method by which to synthesize a variety of nanoscale and mesoscale structures. This method addresses one of the most significant challenges in nanoscience: the in situ parallel placement and synthesis of nano-objects over the mesoscale. The method is based on electroless nanowire deposition on micropatterned substrates (ENDOM). In ENDOM nanostructures are produced at the boundary between two unlike materials if two conditions are met: (a) deposition is kinetically preferred on one of the materials while (b) transport of reactants is favored on the other. In this study, copper structures were deposited on patterned -OH/-CH3-terminated alkanethiolate self-assembled monolayers (SAMs) by exploiting the different reaction rates of electroless deposition on these using the reducing agent dimethylamine borane (DMAB). We demonstrate production of nanowires (width < 100 nm), mesowires (100 nm < width < ∼3000 nm), nanorings, nanopores, and nanochannels. We show that a variety of experimental conditions can be employed, making this method compatible with many substrates. We have also studied the nucleation and growth kinetics of the ENDOM process. The width of the deposit grows exponentially with deposition time and can be modeled using classical nucleation theory. Although the deposit width increases, the height and grain size of the copper deposit is constant (to within experimental uncertainty) with deposition time. These observations indicate that the minimum deposit width is controlled by the nanoparticle dimensions and so can be controlled using the reaction conditions.