This contribution reveals the implications that grain boundary (GB) characteristics have on the microstructure evolution of block copolymer (BCP) thin films during thermal annealing. The analysis was primarily dependent on time-resolved atomic force microscopy (AFM) imaging at high temperature performed on asymmetric poly(styrene-b-methyl methacrylate) (PS-PMMA) BCPs spin-cast on topologically patterned Si3N4 substrates. Image processing techniques were applied to supplement the microstructure analysis presenting structural parameters such as the distribution of BCP cylinder orientations as well as type and frequency of GBs. With this established experimental method, the evolution of cylinder orientation distribution from random to aligned was interpreted in terms of GB migration driven by the interfacial energy discrepancy between PS and PMMA on a silicon nitride substrate. The results demonstrate that velocities of GB migration are strongly dependent on temperature as well as the geometric feature of the GB itself; as the GB tilt angle between neighboring grains increases, GB motion becomes faster. Also, the activation energies of GB migration in BCP structures have been determined and shown to be related to GB tilt angle. The analysis results, implying that both the velocity and the activation energy of GB migration are proportionally related to GB tilt angles, can be understood with the 'compensation effect', which is widely recognized in various thermally activated processes.

Grain boundary migration in cylinder-forming block copolymers leading to uniform cylinder orientation

246th National Meeting (2013)

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