• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.480-480
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• 2010

In the present work, we studied effect of the deposition parameters on the structure and properties of ZnO films deposited by DC arc plasmatron. The varied parameters were gas flow rates, precursor composition, substrate temperature and post-deposition annealing temperature. Vapor of Zinc acetylacetone was used as source materials, oxygen was used as working gas and argon was used as the cathode protective gas and a transport gas for the vapor. The plasmatron power was varied in the range of 700-1,500 watts. Flow rate of the gases and substrate temperature rate were varied in the wide range to optimize the properties of the deposited coatings. After deposition films were annealed in the hydrogen atmosphere in the wide range of temperatures. Structure of coatings was investigated using XRD and SEM. Chemical composition was analyzed using x-ray photo-electron spectroscopy. Sheet conductivity was measured by 4-point probe method. Optical properties of the transparent ZnO-based coatings were studied by the spectroscopy. It was shown that deposition by a DC Arc plasmatron can be used for low-cost production of zinc oxide films with good optical and electrical properties. Sheet resistance of 4 Ohms cm was achieved after the deposition and 30 min annealing in the hydrogen at $350^{\circ}C$. Elevation of the substrate temperature during the deposition process up to $350^{\circ}C$ leads to decreasing of the film's resistance due to rearrangement of the crystalline structure.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.357-363
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• 2015

The development of the environment-friendly tire that meets the standard requirements according to tire labeling system can be improved through using highly homogeneous silica immobilized zinc oxide nanoparticles. In this study, a considerable amount of nanoporous silica was essentially added into nano zinc oxide to improve the physiochemical properties of the formed composite. The introduction of nanoporous silica materials in the composite facilitates the improvement of the wear-resistance and increases the elasticity of the tread. Therefore, the introduction of nanoporous silica can replace carbon black as filler in the formation of composites with desirable properties for conventional green tire. Herein, mesoporous silica immobilized zinc oxide nanoparticle with desirable properties for rubber compounds was investigated. Composites with homogeneous dispersion were obtained in the absence of dispersants. The dispersion stability was controlled through varying the molar ratio, ageing time and mixing order of the reactants. A superior dispersion was achieved in the sample obtained using 0.03 mol of zinc precursor as it had the smallest grain size (50.5 nm) and then immobilized in silica aged for 10 days. Moreover, the specific surface area of this sample was the highest ($649m^2/g$).

• Journal of Information Display
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• v.11 no.3
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• pp.113-118
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• 2010

The effect of hydrogen in the alumina gate insulator on the bottom gate oxide thin film transistor (TFT) with an InGaZnO film as the active layer was investigated. TFT with more H-containing alumina films (TFT A) fabricated via atomic layer deposition using a water precursor showed higher stability under positive and negative bias stresses than that with less H-containing alumina deposited using ozone (TFT B). While TFT A was affected by the pre-vacuum annealing of GI, which resulted in $V_{th}$ instability under NBS, TFT B did not show a difference after the pre-vacuum annealing of GI. All the TFTs showed negative-bias-enhanced photo instability.

• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.363-368
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• 2006

This study selected the optimal catalyst for the process of producing $C_9$-alcohol by hydrogenating $C_9$-aldehyde, and carried out an experiment in order to establish the operating condition for maximizing the yield of $C_9$-alcohol. The BET surface area and the specific area of copper were most excellent in $CuO/ZnO/Al_2O_3$ (60:30:10 wt％) catalyst produced using acetate as a precursor of copper and $Na_2CO_3$ as a precipitant, and the catalyst also showed the highest performance in $C_9$-aldehyde hydrogenation. Using a trickle bed reactor loaded with optimized catalyst, we attained 94.1 wt％ yield of $C_9$-alcohol under the condition of $175^{\circ}C$, 800 psi and $WHSV=3hr^{-1}$. According to the result of comparing with other catalysts used in the hydrogenation of aldehyde, the catalyst showed similar performance to that of Ni/kieselghur and higher than that of $Cu-Ni-Cr-Na/Al_2O_3$ and $Ni-Mo/Al_2O_3$. According to the result of examining the stability of the catalyst through a long-term catalysis test, the yield of $C_9$-alcohol decreased slowly after around 72 hours due to the increasing production of high boiling-point byproducts.

• Journal of the Mineralogical Society of Korea
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• v.21 no.4
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• pp.341-347
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• 2008

The feasibility of commercializing the hydrothermal synthesis of Na-A type zeolite from siliceous mudstone has been conducted using a 50-liter bench-scale autoclave and the application of the zeolite as an environmental remediation agent. Siliceous mudstone, which is widely distributed around the Pohang area, was adopted as a precursor. The siliceous mudstone is favorable for the synthesis of zeolite because it contains 70.7% $SiO_2$ and 10.0% $Al_2O_3$, which are major ingredient of zeolite formation. The synthesis of zeolite was carried out under the following conditions that had been obtained from the previous laboratory-scale tests: 10hr reaction time, $80^{\circ}C$ reaction temperature, $Na_2O/SiO_2$ ratio = 0.6, $SiO_2/Al_2O_3$ ratio = 2.0 and $H_2O/Na_2O$ ratio= 98.6. The crystallinity and morphology of the zeolite formed were similar to those obtained from the laboratory-scale tests. The recovery and cation exchange ion capacity were 95% and 215 cmol/kg, respectively, which are slightly higher than those obtained in laboratory scale tests. To examine the feasibility of the zeolite as an environmental remediation agent, experiments for heavy metal adsorption to zeolite were conducted. Its removal efficiencies of heavy metals in simulated waste solutions decreased in the following sequences: Pb > Cd > Cu = Zn > Mn. In a solution of 1500 mg/L total impurity metals, the removal efficiencies for these impurity metals were near completion (> 99%) except for Mn whose efficiency was 98%. Therefore, the synthetic Na-A type zeolite was proven to be a strong absorbent effective for removing heavy metals.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.29.2-29.2
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• 2010

최근 박막형 LED 및 박막형 태양전지등의 기존 마이크로 소자들의 효율향상을 위한 개선으로 나노구조를 이용한 나노소자 제작이 관심을 받고 있다. 이는 가능성으로만 여겨져왔던 나노기술이 기존 박막형 소자에서 포화된 효율상향 접근방식의 한계에 따른 것으로 생각되며, 나아가 나노기술로 제작된 나노소자가 우리 생활을 채우게 될 날이 얼마남지 않은 것을 의미한다. 특히, 디스플레이 소자에서의 나노기술은 더욱 더 중요시 되고 있다. 그로 인해 투명성과 우수한 광전기적 특성을 지닌 산화물 반도체와 그 나노구조 대한 관심이 날로 높아지고 있으며, 그 가운데 산화아연계(ZnO, MgZnO등) 나노구조를 이용한 나노소자 제작이 많이 연구되고 있다. 산화아연은 c축으로 우선 배향성을 가지는 우르짜이트 구조로써, 나노선 성장이 다른 산화물에 비해 용이하고 그 물리적, 화학적 특성이 안정 우수하다. 이러한 산화아연 나노선 제작법 가운데, 유기금속화학기상증착법은 다른 성장법에 비해 결정학적 광학적 특성이 우수하고 성장속도가 빨라 고품질 나노선 성장에 용이한 장비로 각광받고 있다. 하지만 bottom-up 공정을 기반으로 한 나노소자제작에서 몇 가지 문제점을 가지고 있다. 1) 수직형 대면적 성장, 2) 나노선 밀도 조절의 어려움, 3) 기판과의 계면층에 자발적으로 생성되는 계면층의 제거, 4) 고온성장시 precursor의 증발 문제 등이 그것이다. 이러한 문제점을 해결하기 위해 산화아연 나노구조 성장 시, 마그네슘(Mg)을 도입하여, 각 원소의 조성 차이에 따라 기판 표면에 30nm 두께 미만의 상분리층(단결정+비정질층)을 자발적으로 형성시켰다. 성장이 진행됨에 따라, 아연이 rich한 단결정 층에서는 나노선이 선택적으로 성장하게 하였고, 마그네슘이 rich한 비정질 층에서는 성장이 이루어지지 않게 하였다. 따라서 산화아연이 증발되는 온도영역에서 10nm 이하 직경을 가지는 나노선을 자발적으로 계면층 없이 수직 성장하였다. 또한, 표면의 단결정, 비정질의 사이즈를 Mg 유량으로 적절히 조절한 결과, 산화아연계 나노월 구조성장이 가능하였다.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.101.1-101.1
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• 2010

$Cu(InGa)Se_2$ (CIGS) 태양전지는 박막형 태양전지 중 가장 높은 에너지 변환 효율이 보고 되고 있다. CIGS 태양전지를 제조하는 방법은 3 단계 동시 증착법, 금속 전구체의 셀렌화 공정법, 전기 증착법 등이 있다. 이 중 금속 전구체의 셀렌화 공정법은 다른 제조 방법에 비해 대면적 생산에 유리하고, 비교적 공정 과정이 간단하다는 장점이 있다. 하지만 금속 전구체의 미세구조 및 제조 방법, 셀렌화 공정의 최적화에 대한 연구가 부족하다. 본 실험에서는 후면전극으로 사용되는 Mo 층이 증착된 소다회 유리(soda-lime glass)를 기판으로 사용하였다. Cu-In(4:6), Cu-Ga(6:4) 타겟을 DC 스퍼터링 시스템을 이용하여 금속 전구체를 증착하였다. 이 후 미국 Delawere 대학교의 IEC 연구소와 한국전자통신연구원 (ETRI)에서 금속 전구체의 셀렌화 공정을 진행하였다. 셀렌화 공정 전후의 금속 전구체의 결정 크기와 미세구조의 변화를 관찰하기 위하여 주사전자현미경 (SEM)과 X선 회절 분석기 (XRD)를 사용하였다. 센렌화 공정이 진행된 금속 전구체 위에 버퍼층으로 사용되는 CdS와 전면전극으로 사영되는 ZnO, ITO 층을 합성한 후 에너지 변환 효율을 측정하였다. 최고 효율은 9.7%로 관찰되었다.

• Bulletin of the Korean Chemical Society
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• v.33 no.6
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• pp.1949-1954
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• 2012

We have developed a novel and eco-friendly synthetic route for the preparation of a two-dimensional layered zinc hydroxide with intercalated nitrate anions. The layered zinc hydroxide nitrate, called 'zinc basic salt', was, in general, successfully synthesized, using an electron beam irradiation technique. The 2-propanol solutions containing hydrated zinc nitrate were directly irradiated with an electron-beam at room temperature, under atmospheric conditions, without stabilizers or base molecules. Under electron beam irradiation, the reactive OH radicals were generated by radiolysis of water molecules in precursor metal salts. After further radiolytic processes, the hydroxyl anions might be formed by the reaction of solvated electrons and the OH radical. Finally, the $Zn_5(OH)_8(NO_3)_2{\cdot}2H_2O$ was precipitated by the reaction of zinc cation and hydroxyl anions. Structure and morphology of obtained compounds were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and high resolution transmission electron microscopy (HR-TEM). The chemical components of the products were determined by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA). The thermal behavior of products was studied by thermogravimetric (TG) and differential thermal analysis (DTA).

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.285-285
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• 2010

$Cu(In,Ga)Se_2$ (CIGS) 박막 태양전지 제조에는 동시증발법 (co-evaporation)으로 Cu, In, Ga, Se 각 원소의 증발을 세 단계로 제어하여 CIGS 박막을 증착하는 3-stage 방법이 널리 이용된다[1]. 3-stage 중 1st-stage에서는 In, Ga, Se 원소 만을 증발시켜 $(In,Ga)_2Se_3$ 전구체 (precursor) 박막을 성장시킨다. 고효율의 CIGS 태양전지를 위해서는 $(In,Ga)_2Se_3$ 전구체 증착의 공정 변수와 이에 따른 박막 특성의 이해가 중요하다. 본 연구에서는 Mo 박막이 증착된 소다석회유리 (soda lime glass) 기판에 동시증발장비를 이용하여 280 380 의 기판 온도에서 In, Ga, Se 물질을 증발시켜 $(In,Ga)_2Se_3$/Mo/glass 시료를 제작하였으며 XRD, SEM, EDS 등의 방법을 이용하여 특성을 분석하였다. XRD 분석 결과 기판 온도 $280{\sim}330^{\circ}C$에서는 $(In,Ga)_2Se_3$ 박막의 (006), (300) 피크가 관찰되었으며, 기판 온도가 증가할수록 (006) 피크 세기는 감소하였고 (300) 피크 세기는 증가하였다. $380^{\circ}C$에서는 (110)을 포함한 다수의 피크가 관찰되었다. 그레인 (grain) 크기는 기판 온도가 증가할수록 커지며 Ga/(In+Ga) 조성비는 기판 온도에 따라 일정함을 각각 SEM과 EDS 측정을 통해 알 수 있었다. $(In,Ga)_2Se_3$ 전구체의 (300) 배향은 CIGS 박막의 (220/204) 배향을 촉진하고[2], 이것은 높은 광전변환효율에 기여하는 것으로 알려져 있다. 때문에 $(In,Ga)_2Se_3$의 (300) 피크의 세기가 가장 큰 조건인 $330^{\circ}C$를 1st-stage 증착 온도로 하여 3-stage CIGS 태양전지 공정을 수행하였으며, $MgF_2$/Al/Ni/ITO/i-ZnO/CdS/CIGS/Mo/glass 구조의 셀에서 광전변환효율 16.96%를 얻었다.

• Journal of the Korean Applied Science and Technology
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• v.34 no.1
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• pp.50-57
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• 2017

Zinc oxide is, one of metal oxide semiconductor, harmless to human and environment-friendly. It has excellent chemical and thermal stability properties. Wurtzite-zinc oxide is a large band gap energy of 3.37 eV and high exciton binding energy of 60 meV. It can be applied to various fields, such as solar cells, degradation of the dye waste, the gas sensor. The photocatalytic activity of zinc oxide is varied according to the particle shape and change of crystallinity. Therefore, It is very important to specify the additives and the experimental variables. In this study, the zinc oxide were synthesized by using a microwave assisted hydrothermal synthesis. The precursor was used as the zinc nitrate, the pH value was controlled as 11 by NaOH. Surfactants are the ethanolamine, cetyltrimethylammonium bromide, sodium dodecyl sulfate, sorbitan monooleate was added by changing the concentration. The composite particles had the shape of a star-like, curcular cone, seed shape, flake-sphere. Physical and chemical properties of the obtained zinc oxide was characterized using x-ray diffractometer, field emission scanning electron microscopy, thermogravimetric analysis and optical properties was characterized using UV-visible spectroscopy, photoluminescence and raman spectroscopy.