High-Throughput Characterization of Pattern Formation in Symmetric Diblock Copolymer Films
A P. Smith, Jack F. Douglas, J C. Meredith, Eric J. Amis, Alamgir Karim
Surface pattern formation in thin block copolymer films is investigated utilizing a high throughput methodology to validate the combinatorial measurement approach and to demonstrate the value of the combinatorial method for scientific investigation. We construct measurement libraries from images of sub-regions of block copolymer films having gradients in film thickness and range of molecular mass, M. A single gradient film covers a wide range of film morphologies and contains information equivalent to a large number of measurements of films having a fixed thickness, h. Notably, the scale of the surface patterns are generally much larger than molecular dimensions to that the interpretation of the patterns is more subtle than ordering in bulk block copolymer materials and there is no predictive theory of this type of surface pattern formation. We observe a succession of surface patterns that repeat across the film with increasing h [extended smooth regions, regions containing circular islands, labyrinthine (spinodal) patterns, holes and smooth regions again]. The extended smooth regions and the labyrinthine patterns appear to be novel features revealed by our combinatorial study and these patterns occur as bands of h that are quantized by integral multiples of the bulk lamellar period, Lo. The magnitude of the height gradient influences the width of the bands and the smooth regions occupy an increasing fraction of the film surface area with increasing film gradient. The average size of the spinodal patterns, λ, is found to scale as λ Lo-2.5 or λ M-1.5. The hole and island features have a size comparable to λ and so their size likewise decreases with increasing M. The smooth regions are attributed to an increase in the surface chain density in the outer brush-like block copolymer layer with increasing h and the scaling of λ with M is interpreted in terms of the increasing surface rigidity with M. Further measurements are required to confirm these interpretations, however
, Douglas, J.
, Meredith, J.
, Amis, E.
and Karim, A.
High-Throughput Characterization of Pattern Formation in Symmetric Diblock Copolymer Films, Journal of Polymer Science Part B-Polymer Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851825
(Accessed December 7, 2023)