Mapping the Dynamics of Fluctuations and Defects in Confined Block Copolymer Films with High-Speed Atomic Force Microscopy

The application of block copolymer (BCP) templates for nanofabrication is currently limited by structural disorder of the nanoscale pattern. To study pattern fluctuations and defects, we apply high-speed atomic force microscopy to track the dynamics of confined poly(styrene-block-methyl methacrylate) cylinders during in situ thermal annealing. For this investigation, we use wedge-shaped trenches as a controlled platform for systematically examining the effects of strain and defectivity. By mapping the spatial distribution of domain fluctuations, we identify strong fluctuation enhancement in the vicinity of defect sites. Fluctuations are further influenced by local strain and proximity to the trench sidewalls. To explain these trends, we develop an analytic free-energy model for predicting fluctuations in confined BCP. Finally, we leverage our high-speed imaging to directly track defect healing mechanisms in the confined domains. Altogether, these experiments elucidate the collective interactions of defects, fluctuations, and strain during the assembly and alignment of BCP patterns.