Perfectly Ordered Patterns via Corner-Induced Heterogeneous
Nucleation of Self-Assembling Block Copolymers Confined in Hexagonal
Potential Wells
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Abstract
The ordering dynamics of cylinder-forming
diblock copolymer/homopolymer blends confined in hexagonal potential
wells is systematically investigated using time-dependent Ginzburg–Landau
(TDGL) theory. It is demonstrated that a high-efficient method to
obtain large-scale ordered hexagonal patterns is to utilize corner-induced
heterogeneous nucleation processes, in which nucleation events with
controlled positions and orientations are triggered exclusively at
the six corners of the confining hexagonal wells. Subsequent growth
of the six domains originated from the corners leads to the formation
of perfectly ordered patterns occupying the entire hexagonal well.
The heterogeneous nucleation rate is regulated by the homopolymer
concentration as well as the surface potential of the confining walls.
Defect-free hexagonal patterns are obtained in hexagons with a diagonal
size containing up to 61 cylinders (about 2 μm). The robustness
of the method is examined by studying the tolerance window of the
size-commensurability of the confining wells. The results indicate
that controlled heterogeneous nucleation provides an efficient method
for the fabrication of large-scale ordered patterns using graphoepitaxy
of block copolymer self-assembly
