• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.388-388
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• 2011

Graphene, with its unique physical and structural properties, has recently become a proving ground for various physical phenomena, and is a promising candidate for a variety of electronic device and flexible display applications. The physical properties of graphene depend directly on the thickness. These properties lead to the possibility of its application in high-performance transparent conducting films (TCFs). Compared to indium tin oxide (ITO) electrodes, which have a typical sheet resistance of ~60 ${\Omega}/sq$ and ~85% transmittance in the visible range, the chemical vapor deposition (CVD) synthesized graphene electrodes have a higher transmittance in the visible to IR region and are more robust under bending. Nevertheless, the lowest sheet resistance of the currently available CVD graphene electrodes is higher than that of ITO. Here, we report an ingenious strategy, irradiation of MeV electron beam (e-beam) at room temperature under ambient condition,for obtaining size-homogeneous gold nanoparticle decorated on graphene. The nano-particlization promoted by MeV e-beam irradiation was investigated by transmission electron microscopy, electron energy loss spectroscopy elemental mapping, and energy dispersive X-ray spectroscopy. These results clearly revealed that gold nanoparticle with 10~15 nm in mean size were decorated along the surface of the graphene after 1.0 MeV-e-beam irradiation. The fabrication high-performance TCF with optimized doping condition showed a sheet resistance of ~150 ${\Omega}/sq$ at 94% transmittance. A chemical transformation and charge transfer for the metal gold nanoparticle were systematically explored by X-ray photoelectron spectroscopy and Raman spectroscopy. This approach advances the numerous applications of graphene films as transparent conducting electrodes.

• Journal of Powder Materials
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• v.24 no.4
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• pp.321-325
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• 2017

In this study, we investigate the optical properties of InP/ZnS core/shell quantum dots (QDs) by controlling the synthesis temperature of InP. The size of InP determined by the empirical formula tends to increase with temperature: the size of InP synthesized at $140^{\circ}C$ and $220^{\circ}C$ is 2.46 nm and 4.52 nm, respectively. However, the photoluminescence (PL) spectrum of InP is not observed because of the formation of defects on the InP surface. The growth of InP is observed during the deposition of the shell (ZnS) on the synthesized InP, which is ended up with green-red PL spectrum. We can adjust the PL spectrum and absorption spectrum of InP/ZnS by simply adjusting the core temperature. Thus, we conclude that there exists an optimum shell thickness for the QDs according to the size.

• Restorative Dentistry and Endodontics
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• v.14 no.2
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• pp.49-64
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• 1989

The purpose of this study was to evaluate the effect of several materials on the healing process of apical wound. Sixteen mandibular premolars obtained from 4 healthy dogs were used for this study. Under general anesthesia, the pulpal chamber of each tooth was opened and the pulps were extirpated. The root canals were then instrumented with H-file and irrigated with physiologic saline solution ; the apices were purposely perforated and enlarged with the engine K-reamer. In the experimental groups, apical wounds were filled with one of calcium hydroxide, hydroxylapatite, and tricalcium phosphate materials, mixture of each materials and physiologic saline solution, with a lentulo spiral. In the control group, apical wounds were not filled with any material. All the root canals were filled by the lateral condensation technique with gutta-percha cone and ZOE sealer. The access opening of all the teeth were closed with amalgam. On the 10, 20, 40 and 60th day after experiment, experimental animals were sacrificed. Segments of jaws, each containing one tooth, were fixed in 10% formalin solution and decalcified in Plank-Rychlo solution. The specimens were embedded in paraffin and serially sectioned to an average thickness of $6{\mu}m$. The sections were stained by hematoxylin-eosin and Masson's trichrome stain method and examined under light microscope. The results were as follows : 1. In the experimental groups, the new bone formations were observed in apical wounds. 2. Fourty days later, apical wounds were healed by granulation tissue in the experimental groups, but were not healed by granulation tissue in the control group, and the healing process of experimental groups were more rapid than that of control group. 3. Sixty days later, chronic inflammation disappeared in the experimental groups, and the materials used showed biologic affinity to the periapical tissue. 4. In all the groups, the resorption of cementum appeared on the 10th and 20th day after experiment, and the deposition of cementum appeared on the 40th and 60th day after experiment, especially showing narrowness of apical foramen due to newly formed cementum in calcium hydroxide group. 5. Calcum hydroxide and tricalcium phosphate particles were gradually resolved, but hydroxylapatite particles were not resolved through the experimental period.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.85-88
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• 2003

$Sr_xBa_{1-x}Nb_2O_6$(SBN, $025{\leq}x{\leq}0.75$) ceramic is a ferroelectric material with tetragonal tungsten bronze (TTB) type structure, which has a high pyroelectric coefficient and a nonlinear electro-optic coefficient value. In spite of its advantages, SBN has not been investigated well compared to other ferroelectric materials with perovskite structure. In this study, SBN thin film was manufactured by ion beam sputtering technique using the prepared SBN target in Ar/$O_2$ atmosphere. SBN30 thin film of 500 ${\AA}$ was pre-deposited as a seed layer on Pt(l00)/$TiO_2$/$SiO_2$/Si substrate followed by SBN60 deposition up to 4500 ${\AA}$ in thickness. SBN60/SBN30 layer was deposited at different Oxygen amount of 0, 8.1, 17, and 31.8 sccm, respectively. The crystallinity and orientation behavior as well as electric properties of SBN60/SBN30 multi-layer were examined. The deposited layer was uniform and the orientation was shown primarily along (001) plane from XRD pattern. The crystal structure and the electric properties depended on the Oxygen amount, heating temperature and was the best at O2 = 8.1 seem, $750^{\circ}C$. In electric properties of Pt/SBN60/SBN30/Pt thin film capacitor prepared, the remnant polarization (2Pr) value was 13 ${\mu}C/cm^2$, the coercive field (Ec) 75 kV/cm, and the dielectric constant 1492, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.05a
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• pp.9-9
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• 2009

Coated conductor is required to have good critical current property for high efficiency of electric power applications. Until now, long coated conductor does not show high Jc over 3 MA/$cm^2$ in thick superconducting layer because of texture degradation by thick superconducting layer. In this study, in order to overcome this issue, thicker superconducting layer was deposited with optimized conditions to reduce the degradation of critical current density. SmBCO superconducting coated conductor was deposited with 1~3 um of thickness at $750\sim850^{\circ}C$ under 15~20 mTorr of oxygen partial pressure using batch type EDDC( evaporation using drum in dual chamber). The buffered substrate for superconducting layer deposition was used IBAD-MgO template with the architecture of $LaMnO_3/MgO/Y_2O_3/Al_2O_3$/Hastelloy. After fabrication of coated conductor, critical current was measured by 4-prove method under self-magnetic field and 77K. In addition, surface morphology and texture were analyzed by SEM and XRD, respectively. 3 um thick SmBCO coated conductor shows highest $I_C$ values of 638A/cm-w in 1 m long in the world.

• Macromolecular Research
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• v.10 no.4
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• pp.204-208
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• 2002

A linear rod-like molecule, bis[4-(1,3-octadynyl)phenyl] terephthalate (2), consisting of two diacetylenic groups, was prepared. The unsymmetric diacetylene was prepared by the Cadiot-Chodkiewicz coupling reaction of 1-bromohexyne with 4-ethynylphenol and linked to a benzene core by an esterification reaction with terephthaloyl chloride in tetrahydrofuran. The thin film (200 nm thickness) of compound 2 was fabricated by the physical vapor deposition on a glass plate with a thermal evaporator. In the X-ray diffraction (XRD) study, the vapor deposited film on the glass plate showed peaks with d spacings of 19.4, 5.7, and 4.5 $\AA$. This XRD pattern was quite different from that observed for compound 2 isolated by recrystallization from methylene chloride/hexane. The vapor deposited film was polymerized by UV irradiation. Photopolymerization was carried out through a photomask, resulting in a patterned image, where the irradiated part became isotropic.

• Journal of Powder Materials
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• v.25 no.1
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• pp.54-59
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• 2018

Sb-doped $SnO_2$ (ATO) transparent conducting films are fabricated using horizontal ultrasonic spray pyrolysis deposition (HUSPD) to form uniform and compact film structures with homogeneously supplied precursor solution. To optimize the molar concentration and transparent conducting performance of the ATO films using HUSPD, we use precursor solutions of 0.15, 0.20, 0.25, and 0.30 M. As the molar concentration increases, the resultant ATO films exhibit more compact surface structures because of the larger crystallite sizes and higher ATO crystallinity because of the greater thickness from the accelerated growth of ATO. Thus, the ATO films prepared at 0.25 M have the best transparent conducting performance ($12.60{\pm}0.21{\Omega}/{\square}$ sheet resistance and 80.83% optical transmittance) and the highest figure-of-merit value ($9.44{\pm}0.17{\times}10^{-3}{\Omega}^{-1}$). The improvement in transparent conducting performance is attributed to the enhanced carrier concentration by the improved ATO crystallinity and Hall mobility with the compact surface structure and preferred (211) orientation, ascribed to the accelerated growth of ATO at the optimized molar concentration. Therefore, ATO films fabricated using HUSPD are transparent conducting film candidates for optoelectronic devices.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.2 no.4
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• pp.253-262
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• 2004

Construction of tunnels in a deep crystalline host rock for a potential High-Level Radioactive Waste(HLW) repository inevitably generates an excavation disturbed zone (EDZ). There have been a series of debates on whether a permeability in an EDZ increases or not and what would be the maximum depth of an EDZ. Recent studies show mixed opinions on permeability. However, there has been an international consensus on the thickness of an EDZ; 30 cm for TBM and 1 meter for controlled blast. One of the impacts of an EDZ is on determining the distance between adjacent deposition holes. The void gap by the excavation hinders relaxation of temperature profiles so that the current Korean reference designing distance between holes should be stretched out more to keep the maximum temperature in a buffer region below 100 degrees Celsius. The other impact of an EDZ is on the long-term post closure radiological safety. To estimate the impact, the reference scenario, the well scenario, is chosen. Released nuclides diffuse through a bentonite buffer region experiencing strong sorption and reach a fracture surrounded by a porous medium. Inside a fractured porous region, radionuclides migrate by advection and dispersion with matrix diffusion into a porous medium. Finally, they reach a well assumed to be a source of potable water for local residents. The annual individual dose is assessed on this well scenario to find out the significance of an EDZ. A profound sensitivity study was performed, but all results show that the impact is negligible. Even though the role of an EDZ turns out to be limited on overall safety assessment, still it is worthwhile to study the chemical role of an EDZ, such as a potential source for natural colloids, potential sealing of an open fracture by fine clay particles generated by the process of an EDZ, and alteration of a sorption mechanism by an EDZ in the future.

• Transactions on Electrical and Electronic Materials
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• v.9 no.3
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• pp.105-109
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• 2008

Electrical characteristics of organic light-emitting diodes were investigated by varying a hole-size in evaporation boat in the device structure of ITO/tris(8-hydroxyquinoline) aluminum$(Alq_3)$/Al. The device was manufactured using a thermal evaporation under a base pressure of $5{\times}10^{-6}$ Torr. The $Alq_3$ emitting organics were evaporated to be a thickness of 100 nm at a deposition rate of $1.5{\AA}/s$. A cylindrical-shaped evaporation boat was made out of stainless steel with a small size of hole on top of the boat. Several evaporation boats were made having a different hole size on top; 0.8 mm, 1.0 mm, 1.5 mm, and 3.0 mm. We found that when the hole size on top of the evaporation boat is 1.0 mm, the average roughness is rather smoother compared to the other ones. Also, luminance and external quantum efficiency are superior to the others. Compared to the ones from the devices made with the hole-size of 0.8 mm boat. The luminance and external quantum efficiency of the device made with the hole-size of 1.0 mm boat were improved by a factor of seventy and thirty three, respectively. Also operating voltage is reduced to 2 V.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.545-545
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• 2008

Poly-Si is an essential material for floating gate in NAND Flash memory. To fabricate this material within region of floating gate, chemical mechanical polishing (CMP) is commonly used process for manufacturing NAND flash memory. We use colloidal silica abrasive with alkaline agent, polymeric additive and organic surfactant to obtain high Poly-Si to SiO2 film selectivity and reduce surface defect in Poly-Si CMP. We already studied about the effects of alkaline agent and polymeric additive. But the effect of organic surfactant in Poly-Si CMP is not clearly defined. So we will examine the function of organic surfactant in Poly-Si CMP with concentration separation test. We expect that surface roughness will be improved with the addition of organic surfactant as the case of wafering CMP. Poly-Si wafer are deposited by low pressure chemical vapor deposition (LPCVD) and oxide film are prepared by the method of plasma-enhanced tetra ethyl ortho silicate (PETEOS). The polishing test will be performed by a Strasbaugh 6EC polisher with an IC1000/Suba IV stacked pad and the pad will be conditioned by ex situ diamond disk. And the thickness difference of wafer between before and after polishing test will be measured by Ellipsometer and Nanospec. The roughness of Poly-Si film will be analyzed by atomic force microscope.