• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.92-99
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• 2002

This paper is Intended to investigate physical properties and surface glossing of exposed concrete incorporating granulated blast furnace slag(BS). According to test results there is no remarkable variations in fluidity and air content with increase of BS, but unit weight shows decline tendency Compressive strength at later age gains considerably due to potential hydraulicity reaction of BS. It shows that drying shrinkage increases. It is found that low W/B, surface coating and high BS content lead to favorable effects on the surface glossing of exposed concrete because of filling effects on the voids of the concrete. It is improved by about 7 ％ with increase every 10 ％ of BS content. The effects of form pannel kinds on the improvement of surface glossing are in order for acryl, fancy, steel and wood.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.62-68
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• 1999

Ferroelectric $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$(x=0, 0.1, 0.2, 0.3) thin films were deposited on $Pt/SiO_2/Si$ substrate by MOD(Metalorganic Decomposition) process. Metal carboxylate and metal alkoxide were used as precursors, and 2-methoxyethanol, xylene as solvents. After spin coating, thin films were pre-annealed at $400^{\circ}C$, followed by RTA(Rapid Thermal Annealing) and final annealing at $800^{\circ}C$ in oxygen atmosphere. These procedures were repeated three times to obtain thin films with the thickness of $2000{\AA}$. To enhance the nucleation and growth of layered-perovskite phase, thin films were rapid-thermally annealed above $720^{\circ}C$ in oxygen atmosphere. As RTA temperature increased, fluorite phase was transformed to layered-perovskite phase. And the change of Nb contents affected dielectric / electrical properties and microstructure. The ferroelectric characteristics of $Sr_{0.7}/B_{2.3}(Ta_{1-x}Nb_x)_2O_9$ thin film were Pr=8.67 $\mu{C}/cm^2$, Ec=62.4kV/cm and $I_{L}=1.4\times10^{-7}A/cm^2$ at the applied voltage of 5V, respectively.

• Journal of the Korean Ceramic Society
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• v.37 no.8
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• pp.781-786
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• 2000

An Er-doped sulfide fiber was drawn, and its spectroscopic properties were analyzed. Compositions of a 1000 ppmwt Er3+-doped core and an undoped clad were Ge30-Ga1-Asg-S61 and Ge30-As8-S62, in at.%, respectively. Refractive index of the core composition was approximately 0.01 high than that of the clad. In order to enhance the mechanical stability as well as to prevent infiltration of impurity ions such as OH-, an UV-curable polymer was used for the coating. The optical loss of a fiber formed directly from a polymer coated core rod without cladding was ∼15 dB/m at 1.06$\mu\textrm{m}$. In the case of a fiber with core/clad structure, the optical loss was so high that the stimulated emission of erbium fluorescence was not evident. It is believed that presence of inhomogeneous core/clad interface and crystalline aggregates precipitated in the clad region were responsible for the high optical loss. On the other hand, fluorescence characteristics of Er3+ embedded in the core region were more or loss deteriorate compared to fiber preform, which is attributed to the redistribution of the Er ions along with the partial crystallization of the core glass during the fiberization process.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.447-453
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• 2011

The monodisperse spherical $SiO_2$ particles were overcoated with $Y_2O_3:Eu^{3+}$ phosphor layers via a Pechini sol-gel process and the resulting $SiO_2@Y_2O_3:Eu^{3+}$ core-shell phosphors were subsequently annealed at $800^{\circ}C$ at an ambient atmosphere. The crystallographic structure, morphology, and luminescent property of core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and photoluminescence (PL). The spherical, nonagglomerated $SiO_2$ particles prepared by a Stober method exhibited a relatively narrow size distribution in the range of 260-300 nm. The thickness of phosphor shell layer in the core-shell particles can be facilely controlled by varying the coating number of $Y_2O_3:Eu^{3+}$ phosphors. The core-shell structured $SiO_2@Y_2O_3:Eu^{3+}$ phosphors showed a strong red emission, which was dominated by the $^5D_0-^7F_2$ transition (610 nm) of $Eu^{3+}$ ion under the ultraviolet excitation (263 nm). The PL emission properties of $SiO_2@Y_2O_3:Eu^{3+}$ phosphors were also compared with pure $Y_2O_3:Eu^{3+}$ nanophosphors.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.6
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• pp.367-374
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• 2000

This paper presents a method to fabricate freestanding structures by (100) silicon anisotropic etching and nickel electroless plating. The electroless plating process is simpler than the electroplating, and provides good coating uniformity and improved mechanical properties. Furthermore, the (100) silicon anisotropic etching in KOH solution with being aligned to <100> direction provides vertical (100) sidewalls on etched (100) surface. In this paper, the effects of the nickel electroless plating condition on the properties of electroless plated metal structures are investigated to apply fabrication of micro structures and then various micro structures are fabricated by nickel electroless plating. And then, the structures are released by silicon anisotropic etching in KOH solution with a large gap between the structure and the substrate. The fabricated cantilever structures are $210\mum$. wide, $5\mum$. thick and $15\mum$. over the silicon substrate, and the comb structure has the comb electrodes which are $4\mum$. wide and $4.3\mum$. thick separated by$1\mum$. It is released by silicon anisotropic etching in KOH solution. The gap between the structure and the substrate is $2.5\mum$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.7
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• pp.575-582
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• 2000

The Electrical conduction and optical properties of Ta$_{2}$/O$_{5}$ thin films as the insulators in DRAM capacitors were studied. Liquid Ta/sib 2//O sub 5/ were prepared by a sol-gel processing and multiple layers were applied by spin-coating up to thickness of 800$\AA$. At annealing temperature of 300~$600^{\circ}C$ the electrical conduction and specific dielectric constant were discussed the behaivor of carrier were observed by the Thermally Stimulated Current (TSC) at the temperature range of 30~23$0^{\circ}C$. At annealing temperature of 300~$600^{\circ}C$ the samples were found to be amorphous below $600^{\circ}C$ and crystalline over it. The electrical strength was about 2.2 MV/cm at 40$0^{\circ}C$. In spite of noncrystallization over 50$0^{\circ}C$ the increasing of leakage current due to pinholes and increasing creak. The refractive index was obtained maximum (2.2) at 40$0^{\circ}C$. The dielectric constant was obtained maximum(18.6) at 40$0^{\circ}C$. TSC was observed one peak at the temperature range of 30~23$0^{\circ}C$ from sample at 40$0^{\circ}C$. In the case of collecting voltage the peak size is decreased in proportion to collecting voltage and then the peak may be thought carrier to be a ionic space charge.e.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.169-170
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• 2006

In this study, ultra thin films of ferroelectric vinylidene fluoride-trifluoroethylene (VF2-TrFE) copolymer were fabricated on degenerated Si (n+, $0.002\;{\Omega}{\cdot}cm$) using by spin coating method. A 1~5 wt% diluted solution of purified vinylidene fluoride-trifluoroethylene (VF2:TrFE=70:30) in a dimethylformamide (DMF) solvent were prepared and deposited on silicon wafers at a spin rate of 2000~5000rpm for 30 seconds. After annealing in a vacuum ambient at $200^{\circ}C$ for 60 min, upper gold electrodes were deposited by vacuum evaporation for electrical measurement. X-ray diffraction results showed that the VF2-TrFE films on Si substrates had $\beta$-phase of copolymer structures. The capacitance on $n^+$-Si(100) wafer showed hysteresis behavior like a butterfly shape and this result indicates clearly that the dielectric films have ferroelectric properties. The typical measured remnant polarization (2Pr) and coercive filed (EC) values measured using a computer controlled a RT-66A standardized ferroelectric test system (Radiant Technologies) were about $0.54\;C/cm^2$ and 172 kV/cm, respectively, in an applied electric field of ${\pm}0.75\;MV/cm$.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.37-37
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• 2010

Silicate-silsesquioxane or siloxane-silsesquioxane hybrid thin films are strong candidates as matrix materials for ultra low dielectric constant (low-k) thin films. We synthesized the silicate-silsesquioxane hybrid resins from tetraethoxyorthosilicate (TEOS) and methyltrimethoxysilane (MTMS) through hydrolysis and condensation polymerization by changing their molar ratios ([TEOS]:[MTMS] = 7:3, 5:5, and 3:7), spin-coating on Si(100) wafers. In the case of [TEOS]:[MTMS] 7:3, the dielectric permittivity value of the resultant thin film was measured at 4.30, exceeding that of the thermal oxide (3.9). This high value was thought to be due to Si-OH groups inside the film and more extensive studies were performed in terms of electronic, ionic, and orientational polarizations using Debye equation. The relationship between the mechanical properties and the synthetic conditions of the silicate-silsesquioxane precursors was also investigated. The synthetic conditions of the low-k films have to be chosen to meet both the low orientational polarization and high mechanical properties requirements. In addition, we have investigated a new solution-based approach to the synthesis of semiconducting chalcogenide films for use in thin-film transistor (TFT) devices, in an attempt to develop a simple and robust solution process for the synthesis of inorganic semiconductors. Our material design strategy is to use a sol-gel reaction to carry out the deposition of a spin-coated CdS film, which can then be converted to a xerogel material. These devices were found to exhibit n-channel TFT characteristics with an excellent field-effect mobility (a saturation mobility of ${\sim}\;48\;cm^2V^{-1}s^{-1}$) and low voltage operation (< 5 V). These results show that these semiconducting thin film materials can be used in low-cost and high-performance printable electronics.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.270.1-270.1
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• 2013

Zinc oxide (ZnO) is one of the most powerful materials for purifying organic pollutants using photocatalytic activity. In this study, we have introduced a novel method to design highly photoreactive flexible 3 dimensional (3D) ZnO nanocomposite [F-ZnO-m (m: reaction time, min)] by electrospinning and simple-step ZnO growth processing (one-step ZnO seed coating/growth processing). Significantly, the F-ZnO-m could be a new platform (or candidate) as a photocatalytic technology for both morphology control and largearea production. The highest photocatalytic degradation rate ([k]) was observed for F-ZnO-m at 2.552 h-1, which was 8.1 times higher than that of ZnO nanoparticles (NPs; [k] = 0.316 h-1). The enhanced photocatalytic activity of F-ZnO-m may be attributed to factors such as large surface area. The F-ZnO-m is highly recyclable and retained 98.6% of the initial decolorization rate after fifteen cycles. Interestingly, the F-ZnO-m samples show very strong antibacterial properties against both Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) after exposure to UV-light for 30 min. The antibacterial properties of F-ZnO-m samples are more effective than those of ZnO NPs. More than 96.6% of the E. coli is sterilized after ten cycles. These results indicate that F-ZnO-m samples might have utility in several promising applications such as highly efficient water/air treatment and inactivation of pathogenic microorganisms.

• Korean Journal of Materials Research
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• v.26 no.2
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• pp.84-89
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• 2016

We present the rectifying and nitrogen monoxide (NO) gas sensing properties of an oxide semiconductor heterostructure composed of n-type zinc oxide (ZnO) and p-type copper oxide thin layers. A CuO thin layer was first formed on an indium-tin-oxide-coated glass substrate by sol-gel spin coating method using copper acetate monohydrate and diethanolamine as precursors; then, to form a p-n oxide heterostructure, a ZnO thin layer was spin-coated on the CuO layer using copper zinc dihydrate and diethanolamine. The crystalline structures and microstructures of the heterojunction materials were examined using X-ray diffraction and scanning electron microscopy. The observed current-voltage characteristics of the p-n oxide heterostructure showed a non-linear diode-like rectifying behavior at various temperatures ranging from room temperature to $200^{\circ}C$. When the spin-coated ZnO/CuO heterojunction was exposed to the acceptor gas NO in dry air, a significant increase in the forward diode current of the p-n junction was observed. It was found that the NO gas response of the ZnO/CuO heterostructure exhibited a maximum value at an operating temperature as low as $100^{\circ}C$ and increased gradually with increasing of the NO gas concentration up to 30 ppm. The experimental results indicate that the spin-coated ZnO/CuO heterojunction structure has significant potential applications for gas sensors and other oxide electronics.