Interaction of passivated clusters in solution with micro-patterned surfaces: guided flow versus defect pinning

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Abstract
Gold nanoclusters, chemically passivated with decanethiol and dissolved in toluene, have been deposited from solution onto selected regions of oxidized silicon (100) surfaces patterned either with photoresist or an etched step. When the perimeter of a droplet crosses the boundary between the resist and the silicon surface, we observe transport of cluster solution along such discontinuities, outside of the droplet. Such guided flow can extend for over 600 µm across the surface, producing cluster chains as narrow as ~120 nm, once the toluene has evaporated. The same experiment with an etched step produces no transport of clusters, but rather selective deposition and growth around the discontinuity. These different responses are attributed to the step/boundary material - principally its interaction with the toluene solvent during evaporation.