Facile non-lithographic route to highly aligned silica nanopatterns using unidirectionally aligned polystyrene-block-polydimethylsiloxane films

Thin films (monolayer and bilayer) of cylinder forming polystyrene-block-polydimethylsiloxane (PS-b-PDMS) were shear aligned by the swelling and deswelling of a crosslinked PDMS pad that was physically adhered to the film during solvent vapor annealing. The nanostructures formed by self-assembly were exposed to ultraviolet-ozone to partially oxidize the PDMS, followed by calcination in air at 500 °C. In this process, the PS segments were fully decomposed, while the PDMS yielded silica nanostructures. The highly aligned PDMS cylinders were thus deposited as silica nanolines on the silicon substrate. Using a bilayer film, the center-to-center distance of these features were effectively halved from 38 to 19 nm. Similarly, by sequential shear-alignment of two distinct layers, a rhombic array of silica nanolines was fabricated. This methodology provides a facile route to fabricating complex topographically patterned nanostructures.