Nanostructured organic templates originating from self-assembled block copolymers (BCPs) can be converted into inorganic nanostructures by sequential infiltration synthesis (SIS). This capability is particularly relevant within the framework of advanced lithographic applications because of the exploitation of the BCP-based nanostructures as hard masks. In this work, Al2O3 dot and antidot arrays were synthesized by sequential infiltration of trimethylaluminum and water precursors into perpendicularly oriented cylinder-forming poly(styrene-block-methyl methacrylate) (PS-b-PMMA) BCP thin films. The mechanism governing the effective incorporation of Al2O3 into the PMMA component of the BCP thin films was investigated evaluating the evolution of the lateral and vertical dimensions of Al2O3 dot and antidot arrays as a function of the SIS cycle number. The not-reactive PS component and the PS/PMMA interface in …