A dual functional layer for block copolymer self-assembly and the growth of nanopatterned polymer brushes.

We present a versatile method for fabricating nanopatterned polymer brushes using a cross-linked thin film made from a random copolymer consisting of an inimer (p-(2-bromoisobutyloylmethyl)styrene), styrene, and glycidyl methacrylate (GMA). The amount of inimer was held constant at 20 or 30% while the relative amount of styrene to GMA was varied to induce perpendicular domain orientation in an overlying P(S-b-MMA) block copolymer (BCP) film for lamellar and cylindrical morphologies. A cylinder forming BCP blend with PMMA homopolymer was assembled to create a perpendicular hexagonal array of cylinders, which allowed access to a nanoporous template without the loss of initiator functionality.

Electronic transport and Raman scattering in size-controlled nanoperforated graphene.

We demonstrate the fabrication and study of the structure-property relationships of large-area (>1 cm(2)) semiconducting nanoperforated (NP) graphene with tunable constriction width (w = 7.5-14 nm), derived from CVD graphene using block copolymer lithography. Size-tunable constrictions were created while minimizing unintentional doping by using a dual buffer layer pattern-transfer method.

Chemical patterns from surface grafted resists for directed assembly of block copolymers.

We demonstrate a direct e-beam patternable one-component block copolymer (BCP) resist to fabricate a chemical pattern for the directed assembly of a symmetric block copolymer. The resist consists of a low molecular weight poly(styrene-block-methyl methacrylate) with a hydroxyl group at the PMMA chain end (PS-b-PMMA-OH), which anchors the chains to the surface. This short-tethered PMMA block provided sufficient sensitivity to allow scission by e-beam.

Resist free patterning of nonpreferential buffer layers for block copolymer lithography.

We report the design of a direct electron beam patternable buffer layer to spatially control the orientation of the microdomains in an overlaying polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) block copolymer (BCP) film. The buffer layer consists of a surface anchored low molecular weight PS-b-PMMA, with the PMMA segment anchored to the surface and a short PS block at the buffer layer/BCP interface. The block architecture of the buffer layer combines the essential features of "bottom up" and "top down" approaches as it functions as a nonpreferential layer to dictate perpendicular orientation of BCP domains from the substrate interface and as an e-beam resist to allow top-down lithographic process to spatially define the buffer layer on the substrate.

Fabrication and characterization of large-area, semiconducting nanoperforated graphene materials.

We demonstrate the fabrication of nanoperforated graphene materials with sub-20-nm features using cylinder-forming diblock copolymer templates across >1 mm(2) areas. Hexagonal arrays of holes are etched into graphene membranes, and the remaining constrictions between holes interconnect forming a honeycomb structure. Quantum confinement, disorder, and localization effects modulate the electronic structure, opening an effective energy gap of 100 meV in the nanopatterned material.

One-Step Direct-Patterning Template Utilizing Self-Assembly of POSS-Containing Block Copolymers.

We report the self-assembly of organic-inorganic block copolymers (BCP) in thin-films by simple solvent annealing on unmodified substrates. The resulting vertically oriented lamellae and cylinders are converted to a hard silica mask by a single step highly selective oxygen plasma etching. The size of the resulting nanostructures in the case of cylinders is less than 10 nm.

Cross-linked random copolymer mats as ultrathin nonpreferential layers for block copolymer self-assembly.

We report the effect of increasing amounts of glycidyl methacrylate (GMA) in random copolymers of P(S-r-MMA-r-GMA) on the formation of nonpreferential mats for the assembly of P(S-b-MMA) block copolymers. Increasing the GMA concentration in the random copolymer from 1 (PG1) to 4 (PG4) mole % increased the cross-linking efficiency and reduced the effective minimum thickness of the cross-linked mat for perpendicular alignment of P(S-b-MMA) from approximately 6 nm to approximately 2 nm. The compositional window (so-called perpendicular window) of PG4 was defined for both symmetric and asymmetric P(S-b-MMA).