One-step solution

A direct metal imprinting method uses metal nanoparticles to form arrays of nanodots and nanowires at low temperatures and pressures

Credit: © 2007 ACS

Conventional metal nanoimprinting — a surface patterning technique — is an indirect process where a polymer mould is first created and then used as a mask to etch a metal film. This method involves multiple steps and expensive processes. Now, researchers at the University of California, Berkeley in the US can, in one step, make metallic nanodot and nanowire arrays without using a mask.

Costas Grigoropoulos and colleagues¹ deposited a solution of gold nanoparticles — each coated with a protective monolayer — on a silicon wafer. A polymer mould was then pressed into the solution to make a print. After removing the mould, the patterned nanoparticles were heated until they formed a continuous conducting film.

Viscosity and surface tension of the nanoparticle solution were critical for successful imprinting. The single step metal imprinting technique can produce various nanodot and nanowire arrays with different sizes (down to 100 nm), densities and aspect ratios. In addition, field-effect transistors made with this method perform comparably to those fabricated with conventional photolithography.

Because all the processing and characterization steps can be carried out at low temperatures and under ambient conditions, this new approach can be applied to electronics built on flexible (plastic) substrates.