Nanofabrication by Self-Assembly

Learned from nature, nanostructures can be created by self-assembly of atoms, molecules, nanospheres, DNA strands, and block copolymers. It is a bottom-up approach, comparing to all the top-down technologies introduced in previous chapters. This chapter first describes the rules and forces behind a self-assembly process and then focuses on atom and molecule assembly of monolayer, supermolecules, mesoporous film, and metal-organic frameworks. Using coffee-ring phenomenon as an example, self-assembly of colloidal particles is introduced. To enable a self-assembly to follow a designated path, the process should be guided. Several guiding strategies are described including surface topography, surface energy, electrostatic and magnetic forces, and DNA templates. Apart from the latticelike structures formed from self-assembly, which on their own can be useful, they also can serve as masks for patterning other materials such as the nanosphere lithography and block copolymer lithography described in this chapter. Both use self-assembled structures as masks for subsequent pattern transfer through etching or deposition. Finally, self-regulated porous alumina is introduced as a special case to show how a high aspect ratio nanopore template can be created by a simple anodization process.