Current Position: Lead Scientist at Silicium Energy
Ph.D. Insitution: North Carolina State University (Advisor: Christopher B. Gorman)
Princeton Postdoctoral Research:
A block copolymer consists of chemically different blocks which are covalently connected to each other. It can phase separate into various microdomain structures due to the low entropy of mixing. The volume fraction, the molecular weight, the rigidity of each block, and the strength of the interactions between the segments affect the size, shape, and ordering of the microdomains. Block copolymer thin films which form a sphere or cylinder phase, with a microdomain length scale of a few tens of nanometers, can be used for nanofabrication. External forces like shear, thermal/solvent annealing, and electric fields are often applied to attain long-range order in block copolymer thin films supported on substrates. The chemical properties of each block in the self- assembled block copolymer microdomains provide us with many possible approaches to construct nanostructures. For example, the polyisoprene block in polystyrene-block-polyisoprene can be selectively removed by ozonation, resulting in an efficient patterned mask for reactive ion etching. Dry etch selectivity is also attainable through selective staining of one block. Although only a limited variety of patterns are available using self-assembled block copolymers, the parallel nature of this method makes it attractive for the fabrication of large-area, highly ordered periodic nanostructures.
Current efforts include block copolymer templated electroplating, pattern transfer of shear oriented block copolymer films, fabrication of PDMS replicas for soft lithography, fabrication of anisotropic micron-scale colloidal particles from block copolymers, and the fabrication of biosensors.