Sequential infiltration synthesis (SIS) has emerged in the past decade as a powerful technique for growth of inorganic materials within polymers through atomic layer deposition (ALD) chemistry. In SIS, ALD precursors diffuse into the polymer, leading to growth of nanoscale inorganic materials within the polymer volume. This growth enables direct transformation of lithographic patterns and block copolymers (BCP) to inorganic patterns, adding additional degrees of freedom for pattern design and improving pattern transfer. Here, I will present our recent research in the field of SIS. We shed light on the atomic growth of metal oxide clusters and particles within polymers using high-resolution transmission electron microscopy and x-ray absorption spectroscopy. We follow SIS growth from the nanoscale to the macroscale, expanding our understanding of SIS mechanism and the role of polymer chemistry and reversible polymer-precursor interactions on SIS growth. These insights are then applied in nanofabrication-by-design of homopolymer and block copolymer-templated 3D nanostructures. Importantly, we demonstrate 3D heterostructure fabrication, leading to vertical sub-features patterning, using a single SIS process. In this simple SIS process, we grow, simultaneously but spatially-controlled, two metal oxides within BCP templates by controlling the diffusion time of the two metalorganic precursors. This approach can enable multi-material SIS processes and pave the pathway for 3D patterning.
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