Hyoung-Seok Moon

Fabrication and Electrochemical Characterization of TiO2 Three-Dimensional Nanonetwork Based on Peptide Assembly

The three-dimensional network of TiO(2) hollow nanoribbons designed from a peptide assembly using atomic layer deposition is demonstrated as a promising Li secondary battery electrode in this study. The nanoribbon network ensures effective transport of electrons and Li ions due to (i) a well-connected network of nanoribbons and (ii) the hollow structure of each nanoribbon itself, into which Li ions in the electrolyte can readily diffuse. The improved specific capacity, rate capability, and cyclability of the nanonetwork show that the utilization of a nanonetwork of individual hollow ribbons can serve as a promising strategy toward the development of high-performance electrode for Li secondary batteries.

Soft Graphoepitaxy of Block Copolymer Assembly with Disposable Photoresist Confinement

We demonstrate soft graphoepitaxy of block copolymer assembly as a facile, scalable nanolithography for highly ordered sub-30-nm scale features. Various morphologies of hierarchical block copolymer assembly were achieved by means of disposable topographic confinement of photoresist pattern. Unlike usual graphoepitaxy, soft graphoepitaxy generates the functional nanostructures of metal and semiconductor nanowire arrays without any trace of structure-directing topographic pattern. Our novel approach is potentially advantageous for multilayer overlay processing required for complex device architectures.

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.

Ultralarge-area block copolymer lithography enabled by disposable photoresist prepatterning.

We accomplished truly scalable, low cost, arbitrarily large-area block copolymer lithography, synergistically integrating the two principles of graphoepitaxy and epitaxial self-assembly. Graphoepitaxy morphology composed of highly aligned lamellar block copolymer film that self-assembled within a disposable photoresist trench pattern was prepared by conventional I-line lithography and utilized as a chemical nanopatterning mask for the underlying substrate. After the block copolymer film and disposable photoresist layer were removed, the same lamellar block copolymer film was epitaxially assembled on the exposed chemically patterned substrate. Highly oriented lamellar morphology was attained without any trace of structure directing the photoresist pattern over an arbitrarily large area.

Peptide-templating dye-sensitized solar cells

A hollow TiO(2) nanoribbon network electrode for dye-sensitized solar cells (DSSC) was fabricated by a biotemplating process combining peptide self-assembly and atomic layer deposition (ALD). An aromatic peptide of diphenylalanine was assembled into a three-dimensional network consisting of highly entangled nanoribbons. A thin TiO(2) layer was deposited at the surface of the peptide template via the ALD process. After the pyrolysis of the peptide template, a highly entangled nanotubular TiO(2) framework was successfully prepared. Evolution of the crystal phase and crystallite size of the TiO(2) nanostructure was exploited by controlling the calcination temperature. Finally, the hollow TiO(2) nanoribbon network electrode was integrated into DSSC devices and their photochemical performances were investigated. Hollow TiO(2) nanoribbon-based DSSCs exhibited a power conversion efficiency of 3.8%, which is comparable to the conventional TiO(2) nanoparticle-based DSSCs (3.5%). Our approach offers a novel pathway for DSSCs consisting of TiO(2) electrodes via biotemplating.

Device-oriented graphene nanopatterning by mussel-inspired directed block copolymer self-assembly

Directed self-assembly of a block copolymer is successfully employed to fabricate device-oriented graphene nanostructures from CVD grown graphene. We implemented mussel-inspired polydopamine adhesive in conjunction with the graphoepitaxy principle to tailor graphene nanoribbon arrays and a graphene nanomesh located between metal electrodes. Polydopamine adhesive was utilized for facile and damage-free surface treatment to complement the low surface energy of pristine graphene. Our process minimizes the damage to the ideal graphitic structures and electrical properties of graphene during the nanopatterning process. Multi-channel graphene nanoribbon arrays and a graphene nanomesh were successfully fabricated between metal electrodes.

Nanodomain swelling block copolymer lithography for morphology tunable metal nanopatterning.

Ordered metal nanopatterns are crucial requirements for electronics, magnetics, catalysts, photonics, and so on. Despite considerable progress in the synthetic route to metal nanostructures, highly ordered metal nanopatterning over a large-area is still challenging. Nanodomain swelling block copolymer lithography is presented as a general route to the systematic morphology tuning of metal nanopatterns from amphiphilic diblock copolymer self-assembly. Selective swelling of hydrophilic nanocylinder domains in amphiphilic block copolymer films during metal precursor loading and subsequent oxygen based etching generates diverse shapes of metal nanopatterns, including hexagonal nanoring array and hexagonal nanomesh and double line array in addition to common nanodot and nanowire arrays. Solvent annealing condition of block copolymer templates, selective swelling of hydrophilic cylinder nanodomains, block copolymer template thickness, and oxygen based etching methods are the decisive parameters for systematic morphology evolution. The plasmonic properties of ordered Au nanopatterns are characterized and analyzed with finite differential time domain calculation. This approach offers unprecedented opportunity for diverse metal nanopatterns from commonly used diblock copolymer self-assembly.

Hybrid functional IrO2-TiO2 thin film resistor prepared by atomic layer deposition for thermal inkjet printheads

Abstract IrO2-TiO2 thin films were prepared by atomic layer deposition using Ir(EtCp)(COD) and titanium isopropoxide (TTIP). The resistivity of IrO2-TiO2 thin films can be easily controlled from 1 500 to 356.7 μωcm by the IrO2 intermixing ratio from 0.55 to 0.78 in the IrO2-TiO2 thin films. The low temperature coefficient of resistance(TCR) values can be obtained by adopting IrO2-TiO2 composite thin films. Moreover, the change in the resistivity of IrO2-TiO2 thin films was below 10% even after O2 annealing process at 600 °C. The step stress test results show that IrO2-TiO2 films have better characteristics than conventional TaN0.8 heater resistor. Therefore, IrO2-TiO2 composite thin films can be used as a heater resistor material in thermal inkjet printhead.

Ultralarge-area block copolymer lithography using self-assembly assisted photoresist pre-pattern

These We accomplished truly scalable, low cost, arbitrarily large-area block copolymer lithography, synergistically integrating the two principles of graphoepitaxy and epitaxial self-assembly. Graphoepitaxy morphology composed of highly aligned lamellar block copolymer film that self-assembled within a disposable photoresist trench pattern was prepared by conventional I-line lithography and utilized as a chemical nanopatterning mask for the underlying substrate. After the block copolymer film and disposable photoresist layer were removed, the same lamellar block copolymer film was epitaxially assembled on the exposed chemically patterned substrate. Highly oriented lamellar morphology was attained without any trace of structure directing the photoresist pattern over an arbitrarily large area.

Effects of Film Thickness and Preferred Orientation on the Dieletric Constants of Hf-Aluminate Films Deposited by PEALD

With the rapid progress of microelectronics industry, metal oxide semiconductor (MOS) devices have been scaled down to the low sub-100 nm level. In order to meet the performance requirements of future generations, The development of high-k materials, such as HfO2, ZrO2 and TiO2 has recently been the focus of intensive efforts to replace SiO2 or silicon oxide/nitride-based systems for the application of capacitor dielectrics, gate oxide, and interpoly dielectrics (IPD). In this study, the thickness changes in Hf aluminate films deposited by PEALD were investigated by modifying the process sequence. Hf-aluminate films were deposited on p-type Si (100) at 250 °C and 3 Torr using PEALD. Tetrakis (ethylmethylamino) hafnium (TEMAHf) (Hf[N(CH3)(C2H5)]4) and trimethyl aluminum (TMA) [Al(CH3)3] were used as precursors, and O2 plasma was used as the oxygen reactant. X-ray diffraction (XRD) analysis using CuKα radiation