• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.555-556
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• 2006

In this paper, we have proposed a novel process using two-step electron beam lithography to fabricate 20 nm T-gates for high performance MODFETs. Two-step lithography reduces electron forward scattering by defining the foot on a thin (100 nm) bottom-layer of polymethyl methacrylate (PMMA) at the second step, the T-gate head having been developed at the first step. Adopting a low temperature development technique for the second step reduces the detrimental effect of head exposure on foot definition. We have shown that 20 nm T-gate can be patterned with this process.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.5
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• pp.712-719
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• 2012

Penetrator with enhanced lateral effect(PELE) is a newconcept projectile, without dynamite and fuze. It consists of high-density jacket, closed at its rear end and filled with a low-density filling material. To study the explosion characteristics of PELE, by AUTODYN-3D code, the calculation models of projectile body and bullet target are established and the process of penetrating aluminum-2024 alloy target of PELE is simulated, and the scattering characteristics after penetrating aluminum-2024 alloy target of PELE are studied by different initial velocity. The explicit finite element analysis of PELE fragmentation was implemented with stochastic failure criterion in AUTODYN-3D code. As expansion of filling, the fragments were obtained velocities and dispersed laterally and further more enhancing the damage area largely. The number and shape of the PELE fragments were different depend on impact velocity and incidence angle of filling which fragment generated during penetration and lateral dispersion process.

• Korean Journal of Materials Research
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• v.16 no.10
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• pp.599-605
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• 2006

N-(3-triethoxysilylpropyl)-1,4-diaminoanthrquinone-2,3-dicarboximide (TESP-DADI), an organic blue pigment, has been prepared and incorporated into silica solid matrix reacting triethyl orthosilicate (TEOS) via sol-gel method. Morphology and microstructure of resulting hybrid pigment were studied employing SEM and TEM. The micrographs and particle size distributions showed that uniform pigment can be obtained employing TEOS-based sol-gel method forming silica core. Particle size distribution of dispersed pigment in water was examined using the technique of dynamic light scattering. The ensuing pigment dispersion ink was subjected to various physicochemical evaluation such as viscosity, surface tension, inkjet stability, storage stability, and color change as inkjet ink using spectrophotometric, and microscopic techniques.

• Journal of the Semiconductor & Display Technology
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• v.16 no.2
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• pp.89-93
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• 2017

For various process pressures, aluminum doped zinc oxide(AZO) films were deposited by in-line pulsed-DC sputtering. The deposited AZO films were optically and electrically investigated and analyzed for the window layers of CIGS solar cell systems. As the pressure was increased from 9 mtorr to 15 mtorr, the thickness of AZO was decreased as a result of scattering and its sheet resistance was rapidly increased. The transmittance of AZO was slightly decreased as the pressure was increased and the calculation of figure of merit(F.O.M) was dependent on the sheet resistance. The structural characteristics of AZO thin films analyzed by X-ray diffraction(XRD) showed no significant dependency according to the pressure.

• Journal of Powder Materials
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• v.16 no.5
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• pp.351-357
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• 2009

A two-step recovery method was developed to produce copper powders from copper chloride waste solution as byproducts of MoO$_3$ leaching process. The first step consisted of replacing noble copper ions with external Fe$^{3+}$ ions which were formed by dissolving iron scraps in the copper chloride waste solution. The replaced copper ions were subsequently precipitated as copper powders. The second step was cementation of entire solution mixture to separate (pure) copper powders from aqueous solution of iron chloride. Cementation process variables of temperature, time, and added amount of iron scraps were optimized by using design of experiment method and individual effects on yield and efficiency of copper powder recovery were investigated. Copper powders thus obtained from cementation process were further characterized using various analytical tools such as XRD, SEM-EDS and laser diffraction and scattering methods.Cementation process necessitated further purification of recovered copper powders and centrifugal separation method was employed, which successfully yielded copper powders of more than 99% purity and average 1$\sim$2$\mu$m in size.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.3
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• pp.129-134
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• 2017

We investigated theoretically the quantum optical transition properties of Si, in quasi 2-Dimensinal Landau splitting system, based on quantum transport theory. We apply the quantum transport theory (QTR) to the system in the confinement of electrons by square well confinement potential under linearly polarized oscillating field. We use the projected Liouville equation method with Equilibrium Average Projection Scheme (EAPS). In order to analyze the quantum transition, we compare the temperature and the magnetic field dependencies of the QTLW and the QTLS on four transition processes, namely, the intra-leval transition process, the inter-leval transition process, the phonon emission transition process and the phonon absorption transition process.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.561-561
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• 2012

Graphene, two dimensional single layer of carbon atoms, has tremendous attention due to its superior property such as fast electron mobility, high thermal conductivity and optical transparency, and also found many applications such as field-effect transistors (FET), energy storage and conversion, optoelectronic device, electromechanical resonators and chemical sensors. Several techniques have been developed to form the graphene. Especially chemical vapor deposition (CVD) is a promising process for the large area graphene. For the electrically isolated devices, the graphene should be transfer to insulated substrate from Cu or Ni. However, transferred graphene has serious drawback due to remaining polymeric residue during transfer process which induces the poor device characteristics by impurity scattering and it interrupts the surface functionalization for the sensor application. In this study, we demonstrate the characteristics of solution-gated FET depending on the removal of polymeric residues. The solution-gated FET is operated by the modulation of the channel conductance by applying a gate potential from a reference electrode via the electrolyte, and it can be used as a chemical sensor. The removal process was achieved by several solvents during the transfer of CVD graphene from a copper foil to a substrate and additional annealing process with H2/Ar environments was carried out. We compare the properties of graphene by Raman spectroscopy, atomic force microscopy(AFM), and X-ray Photoelectron Spectroscopy (XPS) measurements. Effects of residual polymeric materials on the device performance of graphene FET will be discussed in detail.

• Korean Journal of Metals and Materials
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• v.49 no.8
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• pp.649-656
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• 2011

The present study evaluated the microstructures and mechanical properties of severely deformed Ni-30Cr alloys. Cross-roll rolling (CRR) process was introduced as a severe plastic deformation (SPD), and Ni-30Cr alloy sheets were cold rolled to 90% thickness reduction and subsequently annealed at $700^{\circ}C$ for 30 min to obtain the recrystallized microstructure. Electron back-scattering diffraction (EBSD) was introduced to analyze grain boundary character distributions (GBCDs). The application of CRR to the Ni-30Cr alloy was effective in enhancing the grain refinement through heat treatment; consequently, the average grain size was significantly refined from $33{\mu}m$ in the initial material to $0.6{\mu}m$. This grain refinement directly improved the mechanical properties, in which yield and tensile strengths significantly increased relative to those of the initial material. We systematically discuss the grain refinement and accompanying improvement of the mechanical properties, in terms of the effective strain imposed by CRR relative to conventional rolling (CR).

• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.893-899
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• 2011

Fabrication of a complex aluminum alloy by the ARB process using dissimilar aluminum alloys has been carried out. Two-layer stack ARB was performed for up to six cycles at ambient temperature without a lubricant according to the conventional procedure. Dissimilar aluminum sheets of AA1050 and AA5052 with thickness of 1 mm were degreased and wire-brushed for the ARB process. The sheets were then stacked together and rolled to 50% reduction such that the thickness became 1 mm again. The sheet was then cut into two pieces of identical length and the same procedure was repeated for up to six cycles. A sound complex aluminum alloy sheet was successfully fabricated by the ARB process. The tensile strength increased as the number of ARB cycles was increased, reaching 298 MPa after 5 cycles, which is about 2.2 times that of the initial material. The average grain size was $24{\mu}m$ after 1 cycle, and became $1.8{\mu}m$ after 6 cycles.

• Journal of the Korean Wood Science and Technology
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• v.21 no.1
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• pp.21-38
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• 1993

In order to investigate the influence of recycling, a laboratory method simulating the papermaking process was used for assessing the effects of recycling on fiber properties. Sw-BKP, Hw-BKP and BGP were disintegrated and beaten to about 42$^{\circ}$SR-44$^{\circ}$SR by a valley beater. After beating, these pulps were dewatered by centrifuge and dried at 90$^{\circ}C$ for 72hrs. This recycling process(sequence of wetting, defiberating, dewatering and drying) was repeated seven times. Physical, mechanical and optical properties of recycled pulps were evaluated by TAPPI Standards. Morphological changes occurred through recycling process was observed by SEM. Sheet density decreased with recycling. The largest drop in density occurred during the first recycling. The porosity values decreased with recycling. Mechanical properties such as tensile, burst strength and folding endurance, decreased with recycling. However tear strength of Sw-BKP and mixtured pulp increased at the first recycling. Optical properties such as brightness, opacity and light scattering coefficient, increased with recycling. However, brightness of mixtured pulp gradually decreased with recycling. Fibrillated outer layer of the fiber was gradually removed from the surface with recycling. As a result of recycling, crinkles on the fiber surface were found to be more folded.