Self-regulating pseudo-monolayer printing of percolating networks of ZnO nanostructures for macroelectronics

Abstract

A patterned dry transfer printing technique that can generate monolayer-like percolating networks of ZnO nanorods (NRs) has been developed. The method relies on the relative adhesion strength between NR–NR and NR–substrate, as well as soft and elastomeric nature of polydimethylsiloxane (PDMS) stamp material. When the NR–substrate adhesion is stronger than the rod–rod interaction, which is the usual case due to a large difference in the contact area, the printing leads to a monolayer-like percolating network of NRs on substrate. The method exploits the contact area difference between NR–NR and NR–substrate, which is inherent in the systems involving high aspect ratio nanostructures on a soft stamp, without considering the complex and elaborate tailoring of the surface chemistry or energetics. When the stamp has multilayer stacks of nanostructures, the monolayer-like printing can be repeated many times, possibly on a large area substrate, due to the self-regulating printing characteristics. The printed percolating network of semiconductor nanostructures have been used as active channels in thin film transistors, where the better gate coupling due to the pseudo-monolayer leads to higher-performance devices compared to other configurations of nanostructures. This self-regulating, patterned dry transfer printing method may enable high-performance macroelectronics with various functional nanostructured materials that have high aspect ratios.