Quantifying the Interface Energy of Block Copolymer Top Coats

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Science

Background:

• Block copolymers (BCPs) are crucial for templating nanoscale materials.
• BCP lithography is a promising nanomanufacturing technique.
• Orienting BCP lamellae perpendicular to substrates is a significant challenge.

Purpose of the Study:

• To investigate the role of top coats in controlling BCP lamellar orientation.
• To quantitatively determine interfacial energies between top coats and BCP components.
• To establish the relationship between top coat composition and BCP orientation.

Main Methods:

• Qualitative assessment of BCP orientation after annealing with various top coats.
• Quantitative measurement of interfacial widths between top coats and homopolymers.
• Resonant soft X-ray reflectivity (RSRR) to determine Flory-Huggins parameter (χ) and interface energy (γ).

Main Results:

• Top coats can be engineered to provide a neutral interface for BCPs.
• Minimized differences between χ and γ at specific top coat compositions correlate with perpendicular orientation.
• Deviations from neutral compositions increase the difference between χ and γ, hindering desired orientation.

Conclusions:

• Top coat composition critically influences interfacial energetics and BCP orientation.
• Quantitative interfacial energy measurements provide a pathway for designing effective top coats for BCP lithography.
• This work advances the understanding and control of BCP self-assembly for nanomanufacturing.