Polycaprolactone Block Copolymer - guided Nanopatterning via Sequential Infiltration Synthesis*

Nanopatterning is known for its precise positioning of matter at the nanoscale dimensions for the purpose of fabricating device architecture. Patterning at this scale enables control over material properties, surface characteristics, and device performance for a wide range of applications, including semiconductor fabrication, data storage, optics and photonics, and biomedical devices. While conventional lithography techniques such as electron-beam and optical lithography have been used by industry for decades, they are approaching limitations with device dimensions shrinking below 10 nm. As an alternative, sequential infiltration synthesis (SIS) is an effective approach that allows controlled and precise fabrication of patterned nanoscale structures by selectively infiltrating inorganic oxides inside a patterned polymer with interactive functional groups. For SIS template, self-assembled block copolymers (BCPs) of different morphologies have been used as a template. In this regard, polystyrene-block-poly(methylmethacrylate) has not only been used widely as an SIS template but for many other template based nanopatterning work. In this work, we used polystyrene-block-poly(ε-caprolactone) block copolymer as a template for SIS to fabricate aluminum oxide (Al₂O₃) nanostructure patterns. To the best of our knowledge, PS-b-PCL has not been explored for nanopatterning purposes. From that study, we observed a strong and significant deposition of oxide materials in PCL, which is very encouraging to utilize PCL for nanopatterning of different materials. Here, we present scanning electron microscopy (SEM) images of the patterned Al₂O₃ deposition for SIS experiments performed at different temperatures and with multiple SIS cycle numbers. We observed significant Al₂O₃ deposition during the first SIS cycle itself, which is consistent with our previous study. The deposited materials were characterized by Energy-Dispersive X-ray Spectroscopy (EDS) for elemental identification. With the effective interactions and deposition of Al₂O₃ materials in the first SIS cycle itself, PCL can be considered a new and promising polymer for uniform and cost-effective nanopatterning.