Young-Hye La

Graphoepitaxy of cylinder-forming block copolymers for use as templates to pattern magnetic metal dot arrays

We report a method to fabricate high-quality patterned magnetic dot arrays using block copolymer lithography, metal deposition, and a dry lift-off technique. Long-range order of cylindrical domains oriented perpendicular to the substrate and in hexagonal arrays was induced in the block copolymer films by prepatterning the substrate with topographic features and chemically modifying the surface to exhibit neutral wetting behaviour towards the blocks of the copolymer. The uniformity of the domain size and row spacing of block copolymer templates created in this way was improved compared to those reported in previous studies that used graphoepitaxy of sphere-forming block copolymers. The pattern of block copolymer domains was transferred to a pattern of magnetic metal dots, demonstrating the potential of this technology for the fabrication of patterned magnetic recording media.

Pixelated chemically amplified resists: Investigation of material structure on the spatial distribution of photoacids and line edge roughness

Preorganized pixel-forming photoresists were prepared to investigate the effect of well-defined material structures and the spatial distribution of photoacid on line edge roughness of chemically amplified photoresists. Asymmetric poly(styrene)-block-poly(t-butylacrylate) (PS-b-PtBA) diblock copolymers, which formed PS cylinders or spheres within a PtBA matrix, were used as photoresists by adding catalytic amounts of photoacid generators (PAGs). PAGs resided only in the PtBA matrix domain, resulting in the PAG chemistry occurring only in the matrix domain. The pixelated photoresists showed a significant solubility switch after UV or x-ray exposure and postexposure bake, such that the polymer in the exposed regions dissolved in aqueous base solution. Granular structures that were matched with the domain spacing and structure of the block copolymer photoresists were observed on the edge of the patterned features. This model system demonstrated that line edge roughness is directly correlated to the structure ...

Assembly of Nanocrystal Arrays by Block‐Copolymer‐Directed Nucleation

Growing in line: The surface chemistry of self-assembled nanostructured block copolymers is used to control the sites at which semiconducting metal sulfide nanocrystals nucleate and grow on a surface directly from aqueous solutions. This process is a new and general strategy for the bottom-up assembly of functional nanocrystalline materials for a variety of applications.

SELECTIVE CLEAVAGE OF FUNCTIONAL GROUPS IN THE FUNCTIONALIZED ORGANIC MONOLAYERS BY SYNCHROTRON SOFT X-RAYS

Aminosilylated surface was treated with halide-substituted aromatic aldehydes, and the resulting molecular layers were examined with synchrotron X-ray photoelectron spectroscopy at the 2B1 SGM and 4B1 microscopy beamline in the Pohang Accelerator Laboratory. It was observed that the halide group of the film diminished upon the irradiation, but the other bands were constant in terms of the intensity and the shape. This observation indicates that the functional groups of the organic monolayers are cleaved selectively by soft X-rays. The cleavage rate was measured as a function of photon energy and normalized with photon flux. The cleavage is first-order to the concentration of the functional group. Its rate constant is sensitive to the molecular structure of the organic monolayers and the kind of substituents on the aromatic ring.