Effect of local point group symmetry on self-assembly in thin films of block copolymers on topographically patterned substrates.*

We have investigated the self-assembly of a diblock copolymer with spherical morphology on novel topographically patterned substrates. Poly(styrene)-b-poly(ferrocenyldimethylsilane), PS-$b$-PFS, was spin casted to form thin films with a PFS monolayer of spheres morphology. Topographically patterned silicon substrates were fabricated by both electron-beam and interference lithographies. To vary the local point group symmetry, a number of topographical patterns were designed and fabricated. Quasiperiodic arrays of posts allows access to multiple types of local symmetries with the average distance between posts an order of magnitude or more larger than the BCP period. Results for controlling long-range correlations of the BCP morphology and local 4-, 6-, 8-, and 12-fold rotational symmetries will be presented.