Assembly of highly-ordered structures for nanosphere lithography

Fernandez Martinez, Sergio

4. term

Nanotechnology, Master

2016

2016-07-15

141

Nanosfere-litografi bruger et selvorganiseret enkelt lag af små kugler som maske til at mønstre overflader. Ved at kombinere enkel selvorganisering med etableret mønstring lover metoden lavere udstyrsomkostninger samt høj gennemstrømning og storskala fremstilling. Dette speciale undersøger praktiske måder at fremstille sådanne enkeltlags ‘kolloidale krystal’-masker af nano- og mikrosfærer. Vi testede tre metoder: dråbefordampning, dip-coating og Langmuir-Blodgett ved luft/vand-grænsefladen. Med silica-nanosfærer gav dråbefordampning ikke ordnede monolag på hverken hydrofobe eller hydrofile substrater; partiklerne aggregerede, og laterale kapillarkræfter var for svage til at organisere dem. Med polystyrenkugler gav dråbemetoden store områder med hexagonal tæt pakning (et tæt, bikube-lignende mønster) sammen med vakancer og linjedefekter. Dip-coating gav også højt ordnede monolag over store områder, men resultatet var stærkt påvirket af suspensionskoncentration, valg af opløsningsmiddel og udtrækningshastighed, hvilket antyder, at belægningsbetingelser kan optimeres yderligere. Monolag dannet ved luft/vand-grænsefladen med Langmuir-Blodgett viste bedre orden for mikropolystyrenpartikler med domæner af hexagonal pakning samt linjedefekter. De vigtigste udfordringer var kompressionsstabilitet under overførsel og materialetab til subfasen; begge var påvirket af dispersionsopløsningsmidlet og den hydrofilitet, som poly(akrylsyre) på polystyrenoverfladen gav.

Nanosphere lithography uses a self-assembled single layer of tiny spheres as a mask to pattern surfaces. By combining simple self-assembly with established patterning, it promises lower equipment costs and high-throughput, large-area fabrication. This thesis investigates practical ways to make these single-layer “colloidal crystal” masks from nano- and microspheres. We tested three routes: droplet evaporation, dip-coating, and the Langmuir-Blodgett technique at the air/water interface. With silica nanospheres, droplet evaporation did not produce ordered monolayers on either hydrophobic or hydrophilic substrates; particles tended to aggregate, and lateral capillary forces were too weak to organize them. With polystyrene spheres, the droplet method produced large regions of hexagonal close-packed order (a tightly packed, honeycomb-like arrangement) together with vacancies and line defects. Dip-coating also yielded highly ordered monolayers over extended areas, but the outcome depended strongly on suspension concentration, solvent choice, and withdrawal speed, suggesting that the coating conditions can be further optimized. Monolayers formed at the air/water interface using Langmuir-Blodgett showed better order for micro-sized polystyrene particles, with domains of hexagonal packing and line defects. The main challenges were maintaining compression stability during transfer and preventing material loss into the subphase; both were influenced by the dispersion solvent and by the hydrophilicity introduced by poly(acrylic acid) grafted onto the polystyrene surface.

[This abstract was generated with the help of AI]

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Fernandez Martinez, Sergio:

• Assembly of highly-ordered structures for nanosphere lithography (2016)