Ozone-based sequential infiltration synthesis of Al2O3 nanostructures in symmetric block copolymer

TL;DR

This paper demonstrates the use of ozone as an oxygen precursor in sequential infiltration synthesis to create alumina nanostructures within block copolymer films, expanding the range of compatible precursors for nanofabrication.

Contribution

It introduces ozone as a new oxygen precursor for SIS, enabling broader material synthesis options while maintaining selective infiltration in block copolymer templates.

Findings

Ozone effectively infiltrates PS-b-PMMA films to form alumina nanostructures.

Ozone-based SIS produces comparable morphology and chemistry to water-based processes.

The method broadens precursor choices for inorganic nanostructure fabrication.

Abstract

Sequential infiltration synthesis (SIS) provides an original strategy to grow inorganic materials by infiltrating gaseous precursors in polymeric films. Combined with micro-phase separated nanostructures resulting from block copoly-mer (BCP) self-assembly, SIS selectively binds the precursors to only one domain mimicking the morphology of the original BCP template. This methodology represents a smart solution for the fabrication of inorganic nanostructures starting from self-assembled BCP thin films, in view of advanced lithographic application and of functional nanostructure synthesis. The SIS process using Trimethylaluminum (TMA) and H2O precursors in self-assembled PS-b-PMMA BCP thin films established as a model system, where the PMMA phase is selectively infiltrated. However the temperature range allowed by polymeric material restricts the available precursors to highly reactive reagents, such as TMA. In order to extend the SIS methodology and access a wide library of materials, a crucial step is the implementation of processes using reactive reagents that are fully compatible with the initial polymeric template. This work reports a comprehensive morphological (SEM, SE, AFM) and physico-chemical (XPS) investigation of alumina nanostructures synthesized by means of a SIS process using O3 as oxygen precursor in self-assembled PS-b-PMMA thin films with lamellar morphology. The comparison with the H2O-based SIS pro-cess validates the possibility to use O3 as oxygen precursor expanding the possible range of precursors for the fabrication of inorganic nanostructures.