ABSTRACT
While numerous nanostructures, made by many different nanoscale patterning and fabrication methods, have been reported1, we still lack the technology to achieve nanostructure formation with enough regularity and controllability of pattern, size, and shape, to enable expedient and precise scientific studies and engineering applications at the nanoscale. Although serial nano-lithographic techniques such as e-beam, ion-beam, or scanning probe lithography enable direct writing of complex nanoscale patterns, the slow speed of these patterning techniques is not suitable to cover large areas (these techniques typically cover less than 1 mm2 at a time). While the parallel method of X-ray lithography can pattern a large area, it is too expensive for most applications. On the other hand, soft lithography-based methods, such as nanoimprint lithography, replicate patterns in a parallel fashion but need a master mold which should first be manufactured by e-beam or X-ray lithography. Most non-lithographic methods, such as the use of nano templates constituted by self-assembled nanoparticles (e.g., block copolymers or colloidal nanospheres) or nanoporous membrane (e.g., anodic alumina membrane), lack the regularity some applications demand over a large area. For other non-lithographic methods such as the direct growth of nanostructures (e.g., carbon nanotubes or nanofibers), the controllability and regularity of the pattern size and geometry still remains an issue. Various techniques to fabricate a dense array of nanoscale posts have been developed and evaluated in reference 2.
