AlO Dot and Antidot Array Synthesis in Hexagonally Packed Poly(styrene--methyl methacrylate) Nanometer-Thick Films for Nanostructure Fabrication.

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, AlO dot and antidot arrays were synthesized by sequential infiltration of trimethylaluminum and water precursors into perpendicularly oriented cylinder-forming poly(styrene--methyl methacrylate) (PS--PMMA) BCP thin films. The mechanism governing the effective incorporation of AlO into the PMMA component of the BCP thin films was investigated evaluating the evolution of the lateral and vertical dimensions of AlO dot and antidot arrays as a function of the SIS cycle number. The not-reactive PS component and the PS/PMMA interface in self-assembled PS--PMMA thin films result in additional paths for diffusion and supplementary surfaces for sorption of precursor molecules, respectively. Thus, the mass uptake of AlO into the PMMA block of self-assembled PS--PMMA thin films is higher than that in pure PMMA thin films.