• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.420-420
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• 2012

ZnO seed layer were deposited on quartz substrate by sol-gel method and prism-like Al-doped ZnO nanorods (AZO nanorods) were grown on ZnO seed layer by hydrothermal method with various Al concentration ranging from 0 to 2.0 at.%. Structural and optical properties of the AZO nanorods were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), photoluminescence (PL). The diameter of the AZO nanorods was smaller than undoped ZnO nanorods and its diameter of the AZO nanorods decreased with increasing Al concentration. In XRD spectrum, it was observed that stress and full width at half maximum (FWHM) of the AZO nanorods decreased and the 'c' lattice constant increased as the Al concentration increased. From undoped ZnO nanorods, it was observed that the green-red emission peak of deep-level emission (DLE) in PL spectra. However, after Al doping, not only a broad green emission peak but also a blue emission peak of DLE were observed.

• 한국진공학회지
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• 제17권4호
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• pp.365-373
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• 2008

최적화된 량의 황화수소 첨가 가스를 이용하여 실리콘 기판위에 증착된 Fe/Al 박막위에 촉매 화학 기상 증착법을 사용하여 직경이 얇은 다중층 탄소나노튜브가 수직 정렬되어 합성되었다. 주사전자현미경 관측 이미지에서 합성된 탄소나노튜브는 상대적으로 일정한 길이를 가지고 기판에 수직으로 정렬되었다. 투과전자현미경 관측에서 합성된 탄소나노튜브는 10nm 이내의 작은 외경을 가졌고 촉매가 거의 없었다. 평균 튜브의 벽 수는 약 다섯 개이다. 수직 정렬된 직경이 얇은 다중층 탄소나노튜브의 성장 메카니즘이 제시되었다. 수직 정렬된 직경이 얇은 다중층 탄소나노튜브는 $0.1\;{\mu}A/cm^2$의 전류밀도에서 약 $1.1\;V/{\mu}m$ 낮은 턴-온 전계를 나타내었고 $2.7\;V/{\mu}m$의 전계에서 약 $2.5\;mA/cm^2$의 전류밀도를 얻었다. 게다가, 수직 정렬된 직경이 얇은 다중층 탄소나노튜브는 약 $1\;mA/cm^2$의 전류밀도에서 20시간동안 전류밀도 저하 없이 좋은 전계 방출 안정성을 보여주었다.

• Rapid Communication in Photoscience
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• 제4권3호
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• pp.50-53
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• 2015

$SnO_2$ thin films were deposited on fused silica substrate by pulsed laser deposition under transverse magnetic field. We have explored the effects of magnetic field and ablation laser wavelength on the optical properties of laser-induced plasma plume and structural characteristics of the deposited $SnO_2$ films. Optical emission from the plume was monitored using an optical fiber to examine the influence of magnetic field on the population of the excited neutral and ionic species and their decay with times after laser ablation. Also, we employed photoluminescence, x-ray diffraction, and UV-Vis absorption to characterize $SnO_2$ films.

• 한국농림기상학회지
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• 제17권4호
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• pp.326-332
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• 2015

우리나라 밭토양에서 국가고유의 온실가스 배출계수를 개발하기 위하여 2010년부터 2012년까지 봄 배추를 대상으로 재배기간 동안에 $N_2O$를 포집분석한 결과는 다음과 같다. 봄 배추 밭에서의 $N_2O$ 배출량은 정식 후 생육초기인 1개월 정도까지 높게 유지되다가 감소하는 경향을 보였다. 또한 생육초기에 수원지역의 $N_2O$ 배출량이 춘천지역보다 높았는데, 이는 수원의 강수량이 상대적으로 높은데 기인한다고 볼수 있다. 질소비료 시용량이 많을수록 $N_2O$ 배출량이 증가하는 경향을 보였으며, 회귀분석한 결과를 보면 99.8%의 상관성이 보였다. 본 연구에서 3년 동안의 봄 배추 재배기간 중 $N_2O$ 배출량을 분석하여 산정한 국가고유 $N_2O$ 배출계수는 0.0056kg Kg $N_2O-N/kg$ N이였다. 이러한 연구결과는 국가고유 $N_2O$ 배출계수를 등록과 더불어 국가 온실가스 배출량 산정에 적용하여 국가 및 지자체의 온실가스 배출량 감축에도 기여할 것이다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.23.1-23.1
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• 2009

ZnO is of great interest for various technological applications ranging from optoelectronics to chemical sensors because of its superior emission, electronic, and chemical properties. In addition, vertically well-aligned ZnO nanorods on large areas with good optical and structural properties are of special interest for the fabrication of electronic and optical nanodevices. To date, several approaches have been proposed for the growth of one-dimensional (1D) ZnO nanostructunres. Several groups have been reported the MOCVD growth of ZnO nanorods with no metal catalysts at $400^{\circ}C$, and fabricated a well-aligned ZnO nanorod array on a PLD prepared ZnO film by using a catalyst-free method. It has been suggested that the synthesis of ZnO nanowires using a template-less/surfactant-free aqueous method. However, despite being a well-established and cost-effective method of thin film deposition, the use of magnetrons puttering to grow ZnO nanorods has not been reported yet. Additionally,magnetron sputtering has the dvantage of producing highly oriented ZnO film sat a relatively low process temperature. Currently, more effort has been concentrated on the synthesis of 1D ZnO nanostructures doped with various metal elements (Al, In, Ga, etc.) to obtain nanostructures with high quality,improved emission properties, and high conductance in functional oxide semiconductors. Among these dopants, Ga-doped ZnO has demonstrated substantial advantages over Al-doped ZnO, including greater resistant to oxidation. Since the covalent bond length of Ga-O ($1.92\;{\AA}$) is nearly equal to that of Zn-O ($1.97\;{\AA}$), high electron mobility and low electrical resistivity are also expected in the Ga-doped ZnO. In this article, we report the successful growth of Ga-doped ZnO nanorods on c-Sapphire substrate without metal catalysts by magnetrons puttering and our investigations of their structural, optical, and field emission properties.

• Bulletin of the Korean Chemical Society
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• 제34권4호
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• pp.1205-1211
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• 2013

The structural and optical properties of the ZnO, Al-doped ZnO, Ga-doped ZnO, and In-doped ZnO nanorods were investigated using field-emission scanning electron microscopy, X-ray diffraction, photoluminescence (PL) and ultraviolet-visible spectroscopy. All the nanorods grew with good alignment on the ZnO seed layers and the ZnO nanorod dimensions could be controlled by the addition of the various dopants. For instance, the diameter of the nanorods decreased with increasing atomic number of the dopants. The ratio between the near-band-edge emission (NBE) and the deep-level emission (DLE) intensities ($I_{NBE}/I_{DLE}$) obtained by PL gradually decreased because the DLE intensity from the nanorods gradually increased with increase in the atomic number of the dopants. We found that the dopants affected the structural and optical properties of the ZnO nanorods including their dimensions, lattice constants, residual stresses, bond lengths, PL properties, transmittance values, optical band gaps, and Urbach energies.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.311-311
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• 2009

Carbon nanotubes (CNTs) belong to an ideal material for field emitters because of their superior electrical, mechanical, and chemical properties together with unique geometric features. Several applications of CNTs to field emitters have been demonstrated in electron emission devices such as field emission display (FED), backlight unit (BLU), X-ray source, etc. In this study, we fabricated a CNT cathode by using filtration processes. First, an aqueous CNT solution was prepared by ultrasonically dispersing purified single-walled CNTs (SWCNTs) in deionized water with sodium dodecyl sulfate (SDS). The aqueous CNT solution in a milliliter or even several tens of micro-litters was filtered by an alumina membrane through the vacuum filtration, and an ultra-thin CNT film was formed onto the alumina membrane. Thereafter, the alumina membrane was solvated by acetone, and the floating CNT film was easily transferred to indium-tin-oxide (ITO) glass substrate in an area defined as 1 cm with a film mask. The CNT film was subjected to an activation process with an adhesive roller, erecting the CNTs up to serve as electron emitters. In order to measure their luminance characteristics, an ITO-coated glass substrate having phosphor was employed as an anode plate. Our field emitter array (FEA) was fairly transparent unlike conventional FEAs, which enabled light to emit not only through the anode frontside but also through the cathode backside, where luminace on the cathode backside was higher than that on the anode frontside. Futhermore, we added a reflecting metal layer to cathode or anode side to enhance the luminance of light passing through the other side. In one case, the metal layer was formed onto the bottom face of the cathode substrate and reflected the light back so that light passed only through the anode substrate. In the other case, the reflecting layer coated on the anode substrate made all light go only through the cathode substrate. Among the two cases, the latter showed higher luminance than the former. This study will discuss the morphologies and field emission characteristics of CNT emitters according to the experimental parameters in fabricating the lamps emitting light on the both sides or only on the either side.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.352.2-352.2
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• 2016

In recent times, much effort has been concentrated on trivalent rare-earth ions activated ceramics or oxide phosphors to develop display industries due to their promising applications in optoelectronic devices and field-emission displays. To prepare efficient phosphors, citrate sol-gel method is one of the best synthetic methods. Green and blue emissive CaLa2ZnO5:RE3+ nanocrystalline materials are synthesized by a citrate sol-gel method. After the samples annealing at $1100^{\circ}C$, morphological and structural properties are investigated by scanning electron microscope images and X-ray diffraction patterns, respectively. At low electron beam voltage of <5 kV, the visible photoluminescence properties are obtained. Various concentrations of the RE3+ ions exhibited their characteristic emission peaks at different excitation wavelengths, respectively. Similarly, at high electron beam anodic voltage, the cathodoluminescence properties are studied as a function of acceleration voltage and filament current. The chromaticity coordinates are calculated for the optimized CaLa2ZnO5 nanocrystalline luminescent materials.

• 한국전기전자재료학회논문지
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• 제25권3호
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• pp.193-197
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• 2012

$Gd_{1-x}VO_4:{Eu_x}^{3+}$ red phosphors were synthesized with changing the concentration of $Eu^{3+}$ ion by using a solid-state reaction method. The crystal structure, surface morphology, and photoluminescence and photoluminescence excitation properties of the red phosphors were measured by using X-ray diffractometer, field emission-scanning electron microscopy, and florescence spectrometer, respectively. The XRD results showed that the main peak of all the phosphor powders occurs at (200) plane. As for the photoluminescence properties, the maximum excitation spectrum occurred at 306 nm due to the charge transfer band from ${VO_4}^{3-}$ to $Eu^{3+}$ ions and the maximum emission spectrum was the red luminescence peaking at 619 nm when the concentration of $Eu^{3+}$ ion was 0.10 mol.

• International Journal of Concrete Structures and Materials
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• 제18권3E호
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• pp.165-171
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• 2006

Environment-friendly materials are increasingly used as building construction materials nowadays, and the market share of those is growing. Accordingly, the research and developments in terms of environmental value are progressing steadily now. The main characteristics of environmental products are far-infrared radiation, negative-ion emission, electromagnetic wave shielding, and antimicrobial property. These products are often used in mortar and as spray on the finishing material. Nevertheless, there are hardly any research on the functional properties of concrete, the main material in construction field. Thus, we evaluated such basic properties of concrete as slump, compressive strength and air content while using such functional materials as sericite, wood-pattern sandstone, carbon black and nano-metric silver solution to focus on their functional properties like far-infrared radiation, negative ion emission, electro magnetic wave shielding, and antimicrobial activity in this research. The results indicated that the most useful material in the functional materials was carbon black. Sericite and nano-metric silver solution had a little effect on the functional property. Moreover, although wood-pattern sandstone had very high functional property, it exhibited too low compressive strength to be applied, to concrete as a factory product. Antimicrobial property of nano-metric silver solution in the concrete was not clear demonstrated, but if these specimens were to be aged in $CO_2$ gas for a long time, it might be apparent.