Emergent symmetries in block copolymer epitaxy

Yi Ding,Karim R Gadelrab,Hejin Huang,Caroline A Ross,Alfredo Alexander-Katz,Katherine Mizrahi Rodriguez

doi:10.1038/s41467-019-10896-5

Yi Ding, Karim R Gadelrab + Show 4 more

Open Access

https://doi.org/10.1038/s41467-019-10896-5

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Journal: Nature Communications	Publication Date: Jul 5, 2019
Citations: 20	License type: open-access

Affiliation: Massachusetts Institute of Technology

Abstract

The directed self-assembly (DSA) of block copolymers (BCPs) has shown promise in fabricating customized two-dimensional (2D) geometries at the nano- and meso-scale. Here, we discover spontaneous symmetry breaking and superlattice formation in DSA of BCP. We observe the emergence of low symmetry phases in high symmetry templates for BCPs that would otherwise not exhibit these phases in the bulk or thin films. The emergence phenomena are found to be a general behavior of BCP in various template layouts with square local geometry, such as 44 and 32434 Archimedean tilings and octagonal quasicrystals. To elucidate the origin of this phenomenon and confirm the stability of the emergent phases, we implement self-consistent field theory (SCFT) simulations and a strong-stretching theory (SST)-based analytical model. Our work demonstrates an emergent behavior of soft matter and draws an intriguing connection between 2-dimensional soft matter self-assembly at the mesoscale and inorganic epitaxy at the atomic scale.

Highlights

The directed self-assembly (DSA) of block copolymers (BCPs) has shown promise in fabricating customized two-dimensional (2D) geometries at the nano- and meso-scale
The directed self-assembly (DSA) of diblock copolymer (BCPs) thin films enables the design of manifold complex structures such as dot arrays, bent lines, line segments, and other useful patterns[1–5]
The BCP consisted of polystyrene-b-poly-4-vinylpyridine (PS-b-P4VP) with volume fraction of P4VP of 30%, thin films of which formed a perforated lamellar phase under thermal annealing condition (Fig. 1a, PS-bP4VP, center-to-center distance L0 = 43 ± 1 nm, symmetry group p6mm)

Summary

Introduction

The directed self-assembly (DSA) of block copolymers (BCPs) has shown promise in fabricating customized two-dimensional (2D) geometries at the nano- and meso-scale. Our work demonstrates an emergent behavior of soft matter and draws an intriguing connection between 2-dimensional soft matter self-assembly at the mesoscale and inorganic epitaxy at the atomic scale. 1234567890():,; The directed self-assembly (DSA) of diblock copolymer (BCPs) thin films enables the design of manifold complex structures such as dot arrays, bent lines, line segments, and other useful patterns[1–5]. DSA of BCPs can be considered a special case of heteroepitaxy, and in general, understanding the interactions between a template and an overlayer has been critical to epitaxial growth of materials in different fields from soft materials to atomic systems. The simultaneous emergence of nonnative symmetries and superlattice behavior in these BCP selfassemblies demonstrates intriguing similarities between soft matter thin-film structures and inorganic crystal surface reconstructions

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