Large-scale hierarchical organization of nanowires for functional nanosystems

We review recent studies of solution-based hierarchical organization of nanowire building blocks. Nanowires have been aligned with controlled nanometer to micrometer scale separation using the Langmuir-Blodgett technique, transferred to planar substrates in a layer-by-layer process to form parallel and crossed nanowire structures over centimeter length scales, and then efficiently patterned into repeating arrays of controlled dimensions and pitch using photolithography. The hierarchically-organized nanowires open up key opportunities in several general areas of nanoscale science and technology. First, hierarchically-assembled nanowire arrays have been used as masks to define nanometer scale metal lines and surface features over large areas. Second, hierarchically-assembled nanowire arrays have been used to fabricate fully-scalable centimeter size arrays of field-effect transistors in high yields without requiring alignment of individual nanowires to output electrodes. Diverse applications of this approach for enabling a broad range of functional nanosystems, including macroelectronic and sensing applications, are described.