Directed Self-Assembly of Lamellar Copolymers: Effects of Interfacial Interactions on Domain Shape.

The depth-dependent structure of a poly(styrene-b-methylmethacrylate) (PS-PMMA) line grating (46 nm pitch) was calculated from quantitative analysis of small-angle X-ray scattering profiles. These data demonstrate that domain shapes are significantly deformed near the substrate interface, where the local PS domain shape resembles an hourglass. The bulk equilibrium dimension is recovered near the center of a 64 nm thick film. Simulations based on self-consistent field theory suggest that deformations near the substrate are caused by extensive penetration of the copolymer domains into the underlying substrate coating (a PS-brush). These findings suggest that new coatings for block copolymer directed self-assembly should consider copolymer penetration lengths in addition to tailoring surface energetics. Furthermore, given the resolution and ensemble-averaging features of synchrotron X-ray scattering, we argue that it has the potential to emerge as a "gold-standard" or "benchmark" dimensional metrology and library validation tool for high density, sub-10 nm features.

Impact of film thickness on the morphology of mesoporous carbon films using organic-organic self-assembly.

Mesoporous polymer and carbon thin films are prepared by the organic-organic self-assembly of an oligomeric phenolic resin with an amphiphilic triblock copolymer template, Pluronic F127. The ratio of resin to template is selected such that a body-centered cubic (Im3m) mesostructure is formed in the bulk. However, well-ordered mesoporous films are not always obtained for thin films (<100 nm), and this behavior is found to be directly correlated with the initial phenolic resin to template ratio. Furthermore, the symmetry of ordered phases is highly dependent on the number of layers of spheres in the film: Monolayers and bilayers are characterized by hexagonal close-packed (HCP) symmetry, while films with approximately 5 layers of spheres exhibit a mixture of HCP and face-centered orthorhombic (FCO) structures. Ultrathick films having more than 30 layers of spheres are similar to the bulk body-centered cubic symmetry with a preferential orientation of the closest-packed (110) plane parallel to the substrate. Film thickness and initial composition of the carbonizable precursors in the template are critical factors in determining the morphology of mesoporous carbon films. These results provide insight into why difficulties have been reported in producing ultrathin ordered mesoporous carbon films using cooperative organic-organic self-assembly.