Sequential Infiltration Synthesis – Mechanism and Applications of Metal Oxide Growth within Block Copolymers

Sequential infiltration synthesis (SIS) is an emerging technique which harnesses atomic layer deposition (ALD) chemistry for growth of inorganic materials within polymers. The highly selective growth within the polar domains of block copolymers (BCP) makes it attractive method for fabricating hybrid BCP-metal oxide composite with synergic properties as well as for BCP-templated inorganic nanostructure fabrication. However, complete understanding of SIS mechanism is still missing and exploring its application space has only just began.
Here we investigate the principles that govern SIS growth in homopolymers and block copolymers thin films using a combination of in-situ and ex-situ methods. We characterize the diffusion-limited growth profile within the polymers and show its relationship to the polymer chemistry, precursor chemistry, and SIS process parameters. Judicious selection of the BCP enabled SIS growth of even bulky metalorganic precursor and templating SnO₂ porous nanostructure. SIS was also utilized to construct multi-layer BCP-templated Al₂O₃ membranes with tuned 3D pore structure. Finally, fundamental understanding of diffusion and growth in SIS enabled us to template 3D metal oxide heterostructures, opening a pathway of direct 3D nanofabrication from BCP.