Ultrafast Patterning of Nanoparticles by Electrostatic Lithography

Electron beam lithography is one of the best tools for patterning nanostructures, but its usage is limited due to slow processing. To enhance the patterning speed, the authors used a low dose electron beam to generate a “latent” charge pattern image and then create a real pattern by attaching positively charged particles by electrospray. Hard baked 2.3μm thick polymethylmethacrylate substrates were irradiated with a 2keV electron beam with a dose of 50nC∕cm2. Positively charged silver nanoparticles were generated by an electrospray technique in which a nanoparticle solution mixed with hexane was sprayed through a 15μm diameter capillary tip with an applied potential of 4.5kV. Charged nanoparticles were deposited to the charge patterned sites by electrostatic attraction with a resolution of 0.7μm. This patterning approach, which we call “electrostatic lithography,” represents a speed increase of ∼20 times over standard fast electron beam resists that require typical doses of 1μC∕cm2. This approach may lead to a general capability for ultrafast patterning of nanomaterial building blocks including nanoparticles and nanotubes without requiring additional etching or other processing steps.