Combinatorial Mapping of Substrate Step Edge Effects on Diblock Copolymer Thin Film Morphology and Orientation

Abstract

We have used a combinatorial gradient technique to map precisely how the terrace structure and microdomain lattice alignment in a thin film of a sphere-forming diblock copolymer are affected by both the thickness of the copolymer film and the height of a series of parallel step edges fabricated on the substrate. We find that for film thicknesses slightly incommensurate with integer numbers of sphere layers, the step edges act as nucleation sites for regions with one more or one fewer layers of spheres. We also find that for our system, the hexagonal lattice formed by a single layer of spheres on the low side of a step edge is aligned along the direction of the step edge only where the film on the high side is sufficiently thin to support only a wetting layer of copolymer material. This work will guide the tuning of film thickness and step height in future studies and applications of graphoepitaxy in block copolymer films.

Controlled Nanopores in Thin Films of Nonstoichiometrically Supramolecularly Assembled Graft Copolymers

“…The bottom-up approach, based on molecular self-assembly that can utilize molecular-level buildingb locks for nanometerscale pattern formation, has been highlighted as ap romising candidate for next-generation nanopatterning technology due to the easy and cost-effective accessibility to sub-10 nm scale dimensions. [1][2][3][4] Furthermore, even three-dimensionally defined, complex nanostructures can be easily prepared by molecular self-assembly without any expensive additional devices.I np articular,s elf-assembled systemso fm acromolecules have been of great interest, includingb iopolymers, [5] reactive blends, [6][7][8][9] and block copolymers, [10][11][12][13][14] among which block copolymers have been widely utilizedt of abricatet ens-of-nanometer-scale nanopatterns during the last few decades. Thermodynamically incompatible polymers of ab lock copolymerr epel each other and undergo microphase segregation due to covalentl inks between the polymers,g iving rise to nanoscale ordered struc-tures.Bycontrolling the ratio of each block and their molecular weights, avariety of spatially periodict wo-or three-dimensional nanostructures, such as spheres, cylinders, gyroids, and lamellas, can be achieved.…”