Spontaneous Spatial Alignment of Polymer Cylindrical Nanodomains on Silicon Nitride Gratings

We report a simple method to align lying-down cylindrical domains of PS-b-PMMA in the trough regions of 555 nm deep silicon nitride gratings without the aid of an external orientation field. This alignment is perpendicular to the orientation of the grating lines and essentially spans the width of the grating trough. The proposed mechanism involves polymer flow and confinement in small dimensions. Also, regularly spaced bumps of almost uniform size can be formed on the crest regions of the support grating. The thickness dependence of PS-b-PMMA thin film surface morphology is also utilized to generate micron-scale periodic structures on 115 nm deep gratings. These experiments to align microdomains with controlled nanometer-scale spacing can be extended to generate self-organizing nanofabricated surfaces.