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Direct In Situ Observation of the Early‐Stage Disorder–Order Evolution of Perpendicular Lamellae in Thermally Annealed High‐χ Block Copolymer Thin Films
Author(s) -
Chandra Alvin,
Nakatani Ryuichi,
Uchiyama Takumi,
Seino Yuriko,
Sato Hironobu,
Kasahara Yusuke,
Azuma Tsukasa,
Hayakawa Teruaki
Publication year - 2019
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201801401
Subject(s) - materials science , grazing incidence small angle scattering , perpendicular , metastability , surface finish , root mean square , scattering , lamellar structure , condensed matter physics , optics , crystallography , composite material , small angle neutron scattering , neutron scattering , geometry , chemistry , physics , mathematics , electrical engineering , quantum mechanics , engineering
The evolution of well‐ordered, sub‐10 nm, perpendicular lamellae from a disordered state is documented directly using in situ atomic force microscopy, cross‐sectional scanning electron microscopy, and grazing‐incidence small angle X‐ray scattering. Since block copolymer (BCP) self‐assembly occurs on extremely fast time scales, directly imaging the growth of perpendicular lamellae remains challenging. The lack of understanding behind early‐stage self‐assembly and how metastable defects can affect the kinetic behavior near thermodynamic equilibrium prevents the realization of defect‐free thin films. By characterizing the evolution of nanostructures using a high‐χ, perpendicular lamella‐forming BCP, poly(polyhedral oligomeric silsesquioxane)‐ block ‐poly(2,2,2‐trifluoroethyl methacrylate), over a wide temperature range, three stages in the evolution of perpendicular lamellae, characterized mainly by the root‐mean‐squared (rms) roughness, is observed. At temperatures lower than the glass transition temperatures ( T g ), the film retains a smooth, disordered surface (rms roughness = 0.352 ± 0.006 nm), characteristic of spin‐coated films. Near the T g , spinodal decomposition and the appearance of lamellae are detected as the rms roughness increases at 70 °C, before peaking at 82 °C at 0.83 nm, and decaying rapidly with increasing temperatures. Above the T g , the rms roughness returns to 0.35 ± 0.03 nm, as defects are observed to annihilate sequentially.