Defect-free Perpendicular Diblock Copolymer Films: The Synergistic Effect of Surface Topography and Chemistry

TL;DR

This study demonstrates through numerical simulations that combining surface topography and chemical treatment of substrates can reliably produce defect-free, perpendicular lamellar phases in diblock copolymer films, enhancing their potential for nanofabrication.

Contribution

It reveals a synergistic effect of surface roughness and chemical preference in achieving defect-free perpendicular BCP lamellae using self-consistent field theory.

Findings

Synergy between topography and surface chemistry enhances perpendicular lamellae formation.

Defect-free phases are reproducible across various initial conditions and substrate parameters.

The approach suggests economical methods for defect-free BCP film fabrication.

Abstract

We propose a direct self-assembly mechanism towards obtaining defect-free perpendicular lamellar phases of diblock copolymer (BCP) thin films. In our numerical study, a thin BCP film having a flat top surface is casted on a uni-directional corrugated solid substrate. The substrate is treated chemically and has a weak preference toward one of the two BCP components. Employing self-consistent field theory (SCFT), we find that there is an enhanced synergy between two substrate characteristics: its topography (geometrical roughness) combined with a weak surface preference. This synergy produces the desired perpendicular lamellar phase with perfect inplane ordering. Defect-free BCP lamellar phases are reproducible for several random initial states, and are obtained for a range of substrate roughness and chemical characteristics, even for a uni-directional multi-mode substrate roughness. Our theoretical study suggests possible experiments that will explore the interplay between uni-directional substrate corrugation and chemical surface treatment. It may lead to viable and economical ways of obtaining BCP films with defect-free lateral alignment.