Self-annihilation of defects in block-copolymer thin films induced by corrugated substrates

Ultradense perfectly ordered structures with nanometric periodicity are of crucial importance for applications such as microelectronics, data storage media or meta-materials. Herein we demonstrate the use of a polymeric guiding pattern to control the self-assembly of block copolymers into highly-ordered 2D arrays. For this, a sinusoidal surface-relief grating was interferometrically inscribed onto an azobenzene containing copolymer sub-layer. A poly(styrene-$b$-ethylene oxide), PS-$b$-PEO, film was cast on top, resulting in cylinders with a 6-fold coordination. When film thickness reaches a critical value where the PS-$b$-PEO free-surface is smooth and no hint of the underlying sinusoidal pattern is apparent, a defect-free 2D-array of PS-$b$-PEO cylinders is observed over a large surface. Our results show that the surface deformation induced by the topological pattern controls the diffusion of defects and consequently their annihilation.