• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.18.1-18.1
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• 2011

Some applications of carbon nanotubes (CNTs) as field emitters, such as x-ray tubes and microwave amplifiers, require high current emission from a small emitter area. To emit the high current density, CNT emitters should be optimally fabricated in terms of material properties and morphological aspects including high crystallinity, aspect ratio, distribution density, height uniformity, adhesion on a substrate, low outgassing rate during electron emission in vacuum, etc. In particular, adhesion of emitters on the substrate is one of the most important parameters to be secured for high current field emission from CNTs. So, we attempted a novel approach to improve the adhesion of CNT emitters by incorporating metal oxide layers between CNT emitters. In our previous study, CNT emitters were fabricated on a metal mesh by filtrating the aqueous suspensions containing both highly crystalline thin multiwalled CNTs and thick entangled multiwalled CNTs. However, the adhesion of CNT film was not enough to produce a high emission current for an extended period of time even after adopting the metal mesh as a fixing substrate of the CNT film. While a high current was emitted, some part of the film was shown to delaminate. In order to strengthen the CNT networks, cobalt-nickel oxides were incorporated into the film. After coating the oxide layer, the CNT tips seemed to be more strongly adhered on the CNT bush. Without the oxide layer, the field emission voltage-current curve moved fast to a high voltage side as increasing the number of voltage sweeps. With the cobalt-nickel oxide incorporated, however, the curve does not move after the second voltage sweep. Such improvement of emission properties seemed to be attributed to stronger adhesion of the CNT film which was imparted by the cobalt-nickel oxide layer between CNT networks. Observed after field emission for an extended period of time, the CNT film with the oxide layer showed less damage on the surface caused by high current emission.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.5
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• pp.243-248
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• 2017

In this study copper glaze samples were prepared with varying amount of tin oxide, and the chromatic characteristics of glazes were explained on the results of spectrophotometric, crystalline phase, and microstructural analyses. The red color of copper glaze was dissipated with the addition of tin oxide and turned into achromatic color due to the decrease of CIEab values. Tin oxide homogeneously distributed in the glaze layer interfered with the red color generation coming from the growth of Cu nuclei, and formed an alloy with metal copper around bubbles. This resulted in the decrease of metal copper peak intensity with minor $Cu_2O$ peak. With the 3.79 % tin oxide addition the glaze was appeared as gray due to the black color CuO and Cassiterite $SnO_2$ phases.

• Journal of Sensor Science and Technology
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• v.31 no.5
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• pp.337-342
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• 2022

Hydrogen (H₂) gas is widely preferred for use as a renewable energy source owing to its characteristics such as environmental friendliness and a high energy density. However, H₂ can easily reverse or explode due to minor external factors. Therefore, H₂ gas monitoring is crucial, especially when the H₂ concentration is close to the lower explosive limit. In this study, metal oxide materials and their p-n heterojunctions were synthesized by a hydrothermal-assisted dip-coating method. The synthesized thin films were used as sensing materials for H₂ gas. When the H₂ concentration was varied, all metal oxide materials exhibited different gas sensitivities. The performance of the metal oxide gas sensor was analyzed to identify parameters that could improve the performance, such as the choice of the metal oxide material, effect of the p-n heterojunctions, and operating temperature conditions of the gas sensor. The experimental results demonstrated that a CuO/ZnO gas sensor with a p-n heterojunction exhibited a high sensitivity and fast response time (134.9% and 8 s, respectively) to 5% H₂ gas at an operating temperature of 300℃.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.318.1-318.1
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• 2016

Hafnium Oxide (HfOx) has been attracted as a promising gate dielectric for replacing SiO2 in gate stack applications. In this paper, Metal-Oxide-Semiconductor (MOS) capacitor with solution processed HfO2 high-k material as a dielectric were fabricated. The solvent using $HfOCl2{\cdot}8H2O$ dissolve in 2-Methoxy ethanol was prepared at 0.3M. The HfOx layers were deposited on p-type silicon substrate by spin-coating at $250^{\circ}C$ for 5 minutes on a hot plate and repeated the same cycle for 5 times, followed by annealing process at 350, 450 and $550^{\circ}C$ for 2 hours. When the annealing temperature was increased from 350 to $550^{\circ}C$, capacitance value was increased from 337 to 367 pF. That was resulted from the higher temperature of HfOx which have more crystallization phase, therefore dielectric constant (k) was increased from 11 to 12. It leads to the formation of dense HfOx film and improve the ability of the insulator layer. We confirm that HfOx layer have a good performance for dielectric layer in MOS capacitors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.1080-1083
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• 2001

Ultrafine NiO/YSZ composite powders were prepared by using a glycine nitrate process for anode material of solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ composite powders were examined with controlling pH of a precursor solution and the content of glycine. The characteristics of synthesized composite powders were examined with X-ray diffractometer, a BET method with N$_2$absorption, scanning and transmission electron microscopy. The strongly acid precursor solution increased the specific surface area of the synthesized composite powders. This is suggested to be caused by the increased binding of metal ions and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of NH$_3$$\^$+/. After sintering and reducing treatment of NiO/YSZ composite powders synthesized by GNP, the Ni/YSZ pellet showed ideal micro-structure very fine Ni parties of 3-5${\mu}$m were distributed uniformly and fine pores around Ni metal particles were formed, thes, leading to an increase of the triple phase boundary among gas Ni and YSZ.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.268-269
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• 2008

Charging of spacecraft occurs in plasma and radiation environment. Especially, we focused on an accident caused by internal charging in a glass material that was used as the cover plate of solar panel array, and tried to measure the charge distribution in glass materials under electron beam irradiation by using a PEA (Pulsed Electro-Acoustic method) system. In the case of a quartz glass (pure $SiO_2$), no charge accumulation was observed either during or after the electron beam irradiation. On the contrary, positive charge accumulation was observed in glass samples containing metal-oxide components. It is found that the polarity of the observed charges depends on the contents of the impurities. To identify which impurity dominates the polarity of the accumulated charge, we measured charge distributions in several glass materials containing various metal-oxide components and calculated the trap energy depths from the charge decay characteristics of all glass samples.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.335-340
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• 2018

Transition metal oxide materials have attracted widespread attention as Li-ion battery electrode materials owing to their high theoretical capacity and good Li storage capability, in addition to various nanostructured materials. Here, we fabricated a CoO Li-ion battery in which Co nanoparticles (NPs) are deposited into a current collector through electrophoretic deposition (EPD) without binding and conductive agents, enabling us to focus on the intrinsic electrochemical properties of CoO during the conversion reaction. Through optimized Co NP synthesis and electrophoretic deposition (EPD), CoO Li-ion battery with 630 mAh/g was fabricated with high cycle stability, which can potentially be used as a test platform for a fundamental understanding of conversion reaction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.7-7
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• 2010

Indium tin oxide (ITO) - SWNT nano crystalline composites was synthesized at low temperature(${\sim}250^{\circ}C$)using Nano Cluster Deposition technique by Metal Orhoganic Chemical Vapor Deposition method. XRD patterns of ITO- SWNT composite shows pure cubic phases without any secondary phase. I-V measurement gives resistance of 12 ohms for Sn doped (3 wt %) indium oxide-SWNT composites. The electrical conductivity of the nano composites is significantly enhanced compared to the SWNT.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.8
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• pp.711-714
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• 2008

Metal-oxide-semiconductor (MOS) capacitors were fabricated to investigate the plasma damage caused by reactive ion etching (RIE) on (100) oriented silicon-on-insulator (SOI) substrates. The thickness of the top-gate oxide, SOI, and buried oxide layers were 10 nm, 50 nm, and 100 nm, respectively. The MOS/SOI capacitors with an etch-damaged SOI layer were characterized by capacitance-voltage (C-V) measurements and compared to the sacrificial oxidation treated samples and the reference samples without etching. The measured C-V curves were compared to the numerical results from corresponding 2-dimensional (2-D) structures by using a Silvaco Atlas simulator.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.5
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• pp.347-350
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• 2013

By inserting a very thin metal layer of Ag between two outer oxide layers of amorphous silicon indium zinc oxide (SIZO), we fabricated a highly transparent SIZO/Ag/SIZO multilayer on a glass substrate. In order to find the optimized thickness of Ag layers, we investigated the variation of optical properties depending on Ag thickness. It was found that the transition of Ag layer from island formation to a continuous film occurred at a critical thickness. Continuity of the Ag film is very important for optical properties in SIZO/Ag/SIZO multilayer. With about 15 nm thick Ag layer, the multilayer showed a high optical transmittance of 80% at 550 nm and low emissivity in IR.