Photocatalytic Surface Initiation for Area-Selective Chemical Vapor Deposition of Polymer Thin Film

Nonlithographic patterning of polymer thin films enables various applications spanning from soft electronics to biomedical engineering. Developing area-selective deposition (ASD) for polymers could achieve self-aligned polymer growth, fostering the generation of complex nanostructures and device configurations with enhanced precision and versatility. However, due to the rapid radical propagation in chain reactions, achieving area-selective radical polymerization in all-dry processes still represents a huge challenge. Here, we report a photocatalytic surface-initiated chemical vapor deposition method. Localized radical generation on the TiO2 surface enabled ASD of a poly(glycidyl methacrylate) (pGMA) thin film. Increasing hydroxyl groups and eliminating Ti(III) defects on the TiO2 surface by the O2 plasma pretreatment were found to be crucial to promote the photocatalytic initiation efficiency. Moreover, we obtained area selectivity of up to 92.2% on prepatterned TiO2/SiO2 substrates with pGMA film thickness over 10 nm on TiO2. Our work offers placement control over chain-growth polymers, providing new opportunities for bottom-up nonlithographic nanofabrication.