Shaping nanomaterials by short electrical pulses

Abstract

We report a new dry-state technique for non-contact patterning of nanostructured conducting materials, and demonstrate its use for carbon nanotube forests and freestanding sheets of carbon nanotubes, graphene, graphene sponge, and MXene. This method uses self-generated electron-emission pulses (∼20 ns) in air. On a substrate—tip separation scale of 10 to 20 nm, the few molecules of gas at atmospheric pressure enables electron-emission-based interaction between a sharp tungsten tip and elements of nanostructured materials. Using the advantages of field enhancement at sharp ends of nanostructured materials, the discharge voltage is reduced to 25–30 V, depending upon the materials density. This method causes largely non-oxidative sequential decomposition of nanostructure elements neighboring the tungsten tip. The main decomposition mechanism is thermal dissociation facilitated by Joule heating and electrostatic removal of debris. The non-contact-based patterning of nanomaterials can be as fast as 10 cm s−1. The resulting precisely patterned structures (<200 nm) are largely free of foreign contaminants, thermal impact and sub-surface structural changes.