Spatiotemporal parallel assembly of metallic wires and particles

1. CNMS User Project Highlight Spatiotemporal parallel assembly of metallic wires and particles • Scientific Achievement • Metallic wires and particles were directed to simultaneously assemble on a surface by manipulating a fluid instability. The current work hinged upon a precise understanding of the nanosecond evolution of competing stable and unstable fluid surface waves along a common fluid stream. #6 1.5 nm #4 1.1 nm #5 1.4 nm #3 1.1 nm #1 0.83 nm #2 0.96 nm • Significance • Combining the formation of particles and wires in a single laser processing step, using a single film strip, overcomes limitations of conventional lithographic methods that are constrained to producing rectangular cross-section wires of lithographic dimensions (or larger) and uniform height. Liquefaction by pulsed laser irradiation transforms a perturbed, Ni thin film strip (1) into an oscillating fluid stream (2) that breaks up into solid nanostructures (2) upon solidification The nature of the initial strip edge perturbation controls the final morphology outcome (wire or particle). • Research Details • CNMS capability: A Ni thin film strip prescribed with a nanoscale edge perturbation was fabricated by electron beam lithography (critical capability) and sputter metallization. • This perturbation was designed to (1) transform into a fluid stream (2) which retained the imposed perturbation and (3) ultimately fragmented into either droplets or wires. • KrF (248nm) laser pulses (18nms pulse width) induced the solid–to–liquid phase transformation while rapid re-solidification preserved the fidelity of the wires/particles formed in the liquid phase. Cover art demonstrating wire and particle assembly as a time-lapse collage highlighting solid strip formation, fluid stream development and the final particle morphology. J.D. Fowlkes, L. Kondic, J.A. Diez, A. G. Gonzalez, Y. Wu, N.A. Roberts, C.E. McCold, and P.D. Rack, Nanoscale.DOI: 10.1039/C2NR31637D