Morphology and wettability control of silicon cone arrays using colloidal lithography.

In this paper we present a simple method to fabricate ordered silicon cone arrays with controllable morphologies on a silicon substrate using reactive ion etching with two-dimensional silica colloidal crystals as masks. The etching process and the morphologies of the obtained structure are quantified. Unlike works reported previously, we show that the surface roughness of the obtained silicon cone arrays can be adjusted by controlling the etching duration, which is proved to be of importance in tailoring the behavior of water droplets when being used as antireflection coatings with superhydrophobicity. Moreover, this strategy is compatible with the methods we have established on controlling the arrangement of colloidal spheres, and thus silicon cone arrays with tunable periodicities, different lattice structures, and various patterns can be prepared. The obtained silicon cone arrays with strips can be used as hydrophobic substrates with anisotropic dewetting just like the leaves of rice. It is found that by adjusting the strip width with and without silicon cones, the water droplets can transform from isotropic dewetting to anisotropic dewetting.