Dong Ok Shin

Mussel‐Inspired Block Copolymer Lithography for Low Surface Energy Materials of Teflon, Graphene, and Gold

Mussel-inspired interfacial engineering is synergistically integrated with block copolymer (BCP) lithography for the surface nanopatterning of low surface energy substrate materials, including, Teflon, graphene, and gold. The image shows the Teflon nanowires and their excellent superhydrophobicity.

One-Dimensional Metal Nanowire Assembly via Block Copolymer Soft Graphoepitaxy

We accomplished a facile and scalable route to linearly stacked, one-dimensional metal nanowire assembly via soft graphoepitaxy of block copolymers. A one-dimensional nanoscale lamellar stack could be achieved by controlling the block copolymer film thickness self-assembled within the disposable topographic confinement and utilized as a template to generate linear metal nanowire assembly. The mechanism underlying this interesting morhpology evolution was investigated by self-consistent field theory. The optical properties of metal nanowire assembly involved with surface plasmon polariton were investigated by first principle calculations.

Surface Energy Modification by Spin-Cast, Large-Area Graphene Film for Block Copolymer Lithography

We demonstrate a surface energy modification method exploiting graphene film. Spin-cast, atomic layer thick, large-area reduced graphene film successfully played the role of surface energy modifier for arbitrary surfaces. The degree of reduction enabled the tuning of the surface energy. Sufficiently reduced graphene served as a neutral surface modifier to induce surface perpendicular lamellae or cylinders in a block copolymer nanotemplate. Our approach integrating large-area graphene film preparation with block copolymer lithography is potentially advantageous in creating semiconducting graphene nanoribbons and nanoporous graphene.

Multicomponent Nanopatterns by Directed Block Copolymer Self-Assembly

Complex nanopatterns integrating diverse nanocomponents are crucial requirements for advanced photonics and electronics. Currently, such multicomponent nanopatterns are principally created by colloidal nanoparticle assembly, where large-area processing of highly ordered nanostructures raises significant challenge. We present multicomponent nanopatterns enabled by block copolymer (BCP) self-assembly, which offers device oriented sub-10-nm scale nanopatterns with arbitrary large-area scalability. In this approach, BCP nanopatterns direct the nanoscale lateral ordering of the overlaid second level BCP nanopatterns to create the superimposed multicomponent nanopatterns incorporating nanowires and nanodots. This approach introduces diverse chemical composition of metallic elements including Au, Pt, Fe, Pd, and Co into sub-10-nm scale nanopatterns. As immediate applications of multicomponent nanopatterns, we demonstrate multilevel charge-trap memory device with Pt-Au binary nanodot pattern and synergistic plasmonic properties of Au nanowire-Pt nanodot pattern.

Flexible and transferrable self-assembled nanopatterning on chemically modified graphene.

Figure 1 . (a) Transferrable self-assembled nanopatterning procedure. See text for details. SEM images of lamellar BCP nanotemplates transferred onto (b) right angled fracture edge of silicon wafer and (c) microscale ZnO hillock. (d) Photograph and (e) SEM image of cylindrical BCP nanotemplates transferred onto syringe needle surface. Block copolymer (BCP) self-assembly generates dense and periodic nanodomains, whose characteristic dimensions can be as small as 3 nm. [ 1–3 ] Such self-assembly in thin fi lms can create two-dimensional lithographic nanotemplates with pattern precision barely attainable by other methods. [ 4–9 ] Substantial progress in the synergistic integration of BCP selfassembly with e-beam lithography and ArF or other photolithography, demonstrates that this self-assembly based nanopatterning is a promising technology to complement the resolution limit of a conventional lithography. [ 10–20 ] Meanwhile, BCP self-assembled nanopatterning has been regarded as an intrinsic two-dimensional patterning method specifi cally useful for hard and fl at inorganic substrates. [ 4 , 21 ] The wellestablished processing steps involved with the formation of uniform thickness, ultrathin (typically less than 100 nm) BCP fi lm via spin casting and subsequent thermal/solvent annealing are generally considered incompatible to three-dimensional geometries or conventional fl exible polymer substrates with low chemical/thermal stability and surface roughness typically larger than nanoscale. In this work, mechanically robust but compliant chemically modifi ed graphene (CMG) fi lm [ 22 , 23 ] is introduced as a transferrable and disposable substrate for the self-assembled nanopatterning of nonplanar, fl exible, and even multistack device oriented structures. Taking advantage of the high chemical/ thermal stability, genuine atomic scale fl atness, and mechanical robustness with compliance, graphene based materials can be excellent substrates for nanopatterning (Supporting Information, Table S1). [ 24 , 25 ] While pristine graphene has a low surface energy, CMG prepared via

A plasmonic biosensor array by block copolymer lithography

Highly uniform and dense, hexagonal noble metal nanoparticle arrays were achieved on large-area transparent glass substrates via scalable, parallel processing of block copolymer lithography. Exploring their localized surface plasmon resonance (LSPR) characteristics revealed that the Ag nanoparticle array displayed a UV-vis absorbance spectrum sufficiently narrow and intense for biosensing application. A highly-sensitive, label-free detection of prostate cancer specific antibody (anti-PSA) with sub-ng ml−1 level detection limit (0.1∼1 ng ml−1) has been accomplished with the plasmonic nanostructure. Our approach offers a valuable route to a low-cost, manufacture-scale production of plasmonic nanostructures, potentially useful for various photonic and optoelectronic devices.

Block copolymer multiple patterning integrated with conventional ArF lithography

We present block copolymer multiple patterning as an efficient and truly scalable nanolithography for sub-20 nm scale patterning, synergistically integrated with conventional ArF lithography. The directed assembly of block copolymers on chemically patterned substrates prepared by ArF lithography generated linear vertical cylinder arrays with a 20 to 30 nm diameter, enhancing the pattern density of the underlying chemical patterns by a factor of two or three. This self-assembled resolution enhancement technique affords a straightforward route to highly ordered sub-20 nm scale features via conventional lithography.

Bionanosphere Lithography via Hierarchical Peptide Self‐Assembly of Aromatic Triphenylalanine

A nanolithographic approach based on hierarchical peptide self-assembly is presented. An aromatic peptide of N-(t-Boc)-terminated triphenylalanine is designed from a structural motif for the beta-amyloid associated with Alzheimers disease. This peptide adopts a turnlike conformation with three phenyl rings oriented outward, which mediate intermolecular pi-pi stacking interactions and eventually facilitate highly crystalline bionanosphere assembly with both thermal and chemical stability. The self-assembled bionanospheres spontaneously pack into a hexagonal monolayer at the evaporating solvent edge, constituting evaporation-induced hierarchical self-assembly. Metal nanoparticle arrays or embossed Si nanoposts could be successfully created from the hexagonal bionanosphere array masks in conjunction with a conventional metal-evaporation or etching process. Our approach represents a bionanofabrication concept that biomolecular self-assembly is hierarchically directed to establish a straightforward nanolithography compatible with conventional device-fabrication processes.

DNA origami nanopatterning on chemically modified graphene.

thus far.Here we demonstrate that chemically modified grapheneis an excellent substrate material for adsorption and also forspatial patterning of DNA origami structures. Our strategy isto integrate the top-down patterning of chemically modifiedgraphene through conventional photolithography withbottom-up self-assembly of DNA origami structures uponthe patterned chemically modified graphene. Because of thesmoothness at atomic scale and chemical diversity of chemi-cally modified graphene, including GO, reduced grapheneoxide (rGO), and nitrogen-doped reduced graphene oxide(NrGO), the adsorption of DNA origami structures can besystematically tuned to allow spatial patterning on chemicallymodified graphene.Figure 1 illustrates the procedure for patterning of DNAorigami structures. A GO film was spin-cast from aqueoussolution onto an NH

Graphoepitaxy of Block‐Copolymer Self‐Assembly Integrated with Single‐Step ZnO Nanoimprinting

A highly efficient, ultralarge-area nanolithography that integrates block-copolymer lithography with single-step ZnO nanoimprinting is introduced. The UV-assisted imprinting of a photosensitive sol-gel precursor creates large-area ZnO topographic patterns with various pattern shapes in a single-step process. This straightforward approach provides a smooth line edge and high thermal stability of the imprinted ZnO pattern; these properties are greatly advantageous for further graphoepitaxial block-copolymer assembly. According to the ZnO pattern shape and depth, the orientation and lateral ordering of self-assembled cylindrical nanodomains in block-copolymer thin films could be directed in a variety of ways. Significantly, the subtle tunability of ZnO trench depth enabled by nanoimprinting, generated complex hierarchical nanopatterns, where surface-parallel and surface-perpendicular nanocylinder arrays are alternately arranged. The stability of this complex morphology is confirmed by self-consistent field theory (SCFT) calculations. The highly ordered graphoepitaxial nanoscale assembly achieved on transparent semiconducting ZnO substrates offers enormous potential for photonics and optoelectronics.