Optimizing Polymer Brush Coverage To Develop Highly Coherent Sub‑5 nm Oxide Films by Ion Inclusion

• Published in: Chemistry of materials Vol. 31; no. 22; pp. 9338 - 9345
• Main Authors: Lundy, Ross, Yadav, Pravind, Selkirk, Andrew, Mullen, Eleanor, Ghoshal, Tandra, Cummins, Cian, Morris, Michael A
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26-11-2019
• Subjects: Chemical Sciences; Polymers
• ISSN: 0897-4756; 1520-5002
• DOI: 10.1021/acs.chemmater.9b02856

Area-selective deposition is a promising technique for positional self-alignment of materials at a prepatterned surface. Critical to this is the development of molecular systems that have selective surface binding and can act as templates to material growth. This paper reports how end functionalized polymers can be used to create oxide films through a grafting method. Here, we detail a facile approach for rapid grafting (in seconds) of polymer brush films with complete coverage over large areas with high uniformity (pinhole free). Subsequent conversion to an oxide (∼3–4 nm thickness) is performed via liquid-phase metal ion infiltration. Exposing the covalently grafted polymer brush (P2VP-OH) to a metal salt-solvent solution (using the Al3+ ion as a model species) swells the polymer, facilitating ion inclusion. Early results suggest that a solvent-mediated approach to polymer film infiltration can be used to develop inorganic films in a facile process. While data shows inclusion into both large-area and patterned films, the mechanism and understanding of these have been limited. In particular, the solution-mediated process described here shows the precise tailoring of nanometer-thin polymer films that are pinhole-free and that can be activated to create semiconductor-compatible oxide films that are parallel in quality to ALD- or CVD-derived processes. A surface deactivation strategy is also realized using a hydroxyl-terminated polystyrene (PS-OH) brush that prevents the deposition of ions. We consider this strategy as a means to prevent electromigration of ions as well as the possibility of coating ALD layers.