Self-assembly of cylinder forming diblock copolymers on modulated substrates: a simulation study

TL;DR

This study uses simulation methods to analyze how cylinder-forming diblock copolymers self-assemble on modulated substrates, revealing how substrate features influence cylinder orientation for nanotech applications.

Contribution

It provides new insights into the effects of substrate modulation on the orientation of self-assembled copolymer cylinders, highlighting conditions favoring parallel or perpendicular alignment.

Findings

Orthogonal cylinders are favored at low barrier heights with preferential minority block.

Parallel alignment occurs at higher barrier heights near commensurate conditions.

Substrate affinity and barrier shape can be tuned for desired nanostructure assembly.

Abstract

Self-consistent field theory (SCFT) and strong segregation theory (SST) are used to explore the parameter space governing the self-assembly of cylinder forming block copolymers (BCPs) on a modulated substrate. The stability of in-plane cylinders aligning parallel or perpendicular to substrate corrugation is investigated for different barrier height and spacing for a weakly preferential substrate. Within the conditions of our simulations, the results indicate that cylinder alignment orthogonal to substrate undulation is promoted at low barrier height when substrate is preferential to minority block, independent of barrier spacing. Commensurability is shown to play a limited role in the assembly of orthogonal meshes. Parallel alignment is readily achieved at larger barrier height, near condition of commensuration between barrier spacing and polymer equilibrium period. This is particularly true when substrate is attractive to majority block. The interplay between barrier shape and substrate affinity can be utilized in nanotechnology application such as mesh creation, density multiplication, and 3D BCP morphologies.