• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.21-24
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• 2008

Properties of carbon nano fiber (CNF) as field emitters were described. Carbon nano fiber (CNF) of herringbone was prepared by thermal chemical vapor deposition(CVD). Field emitters mixed with organic binders, conductive materials and were prepared by screen-printing process. In order to increase field emissions, the surface treatment of rubbing & peel-off was applied to the printed CNF emitters on cathode electrode. The measurements of field emission properties were carried out by using a diode structure inline vacuum chamber. CNF of herringbone type showed good emission properties that a turn on field was as low as 2.1 $V/{\mu}m$ and current density was as large as 0.15 $mA/cm^2$ of 4.2 $V/{\mu}m$ with electric field. Through the results. we propose that CNFs are suitable for application of electron emitters in Field Emission Devices.

• Journal of Sensor Science and Technology
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• v.16 no.4
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• pp.307-312
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• 2007

The films of Er-doped ZnO (ZnO:Er) were prepared onto MgO wafers by ultrasonic spray pyrolysis at $550^{\circ}C$. The concentration of Er in the deposition source varied from 0.5 wt% to 3.0 wt%. The crystallographic properties and surface morphologies of the films were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. The properties of photoluminescence (PL) for the films were investigated by dependence of PL spectra on the Er concentration in the films. The films were grown as polycrystalline with a dominant direction of [002]. The grain size of the films were reduced by Er-doping. Er-doping enhanced the ultraviolet emission of ZnO:Er films. The ZnO:Er films prepared with the deposition source of 2.0 wt% Er showed the strongest ultraviolet light emission peak among the films in this study.

• 한국정보디스플레이학회:학술대회논문집
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• 2000.01a
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• pp.131-132
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• 2000

We prepared Si emitters coated with a MOCVD $CoSi_2$ layer to improve the emission properties. The $CoSi_2$ layer was grown on Si field emitters in situ by reactive chemical-vapor deposition of cyclopentadienyl dicarbonyl cobalt at 600 ${\sim}$ $650^{\circ}C$. The $CoSi_2$ coated field emitters showed enhanced emission properties of current-voltage characteristics, which were due to the increase of emitting area from Fowler-Nordheim plot. And the emission current fluctuation decreased due to the chemically stable surface properties of $CoSi_2$.

• Journal of the Korean Society of Combustion
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• v.6 no.1
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• pp.36-43
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• 2001

The NOx emission characteristics of jet flames fueled with $H_2\;and\;CH_4$ were studied. Experimental and numerical investigations were carried out for various flames with varying equivalence ratio, fuel flow rate and nozzle diameter. The Emission indices of NOx(EINOx) were measured by chemiluminescent method and calculated by numerical model based on detailed chemistry. The results show that EINOx of $CH_4\;and\;H_2$ flames have different trends in terms of equivalence ratio and fuel flow rate but have the same trends in terms of nozzle diameter. These differences can be explained by the following Thermal and Prompt trends in both flames. Thermal EINOx is quite sensitive to the residence time in the high-temperature region weighted by the maximum flame temperature. Prompt EINOx is mainly influenced by flame surface area of each combustion conditions.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.6
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• pp.531-537
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• 2014

Terrestrial vegetation has been known as a main source of biogenic volatile organic compounds (BVOCs). Isoprene and monoterpene among the BVOCs are most abundant species emitted by forests, and have a significant impact on atmospheric chemistry. Abundancy of these species could lead to an increase or decrease in the production of natural tropospheric ozone in forests, depending on the nitric oxide (NO) concentration. Soil is the most significant source of natural NO. Understanding of NO emission from forest soil could be critical in evaluation of air quality in the forest area. Flux-gradient similarity theory (FGST) was applied for practical use to estimate forest soil NO emission at Mt. Taewha where is available micro-meteorological data near surface monitoring from flux tower. NO fluxes calculated by FGST were compared to flux results by flow-through dynamic chamber (FDC) measurement. Surface NO emission trends were shown between two different techniques, however their magnitudes were found to be different. NO emissions measured from FDC technique were relatively higher than those from theoretical results. Daily mean NO emissions resulted from FGST during Aug. 13, 14 and 15 were $0.28{\pm}8.45$, $2.17{\pm}15.55$, and $-3.18{\pm}13.65{\mu}gm^{-2}hr^{-1}$, respectively, while results from FDC were $2.26{\pm}1.44$, $5.11{\pm}3.85$, and $2.23{\pm}6.45{\mu}gm^{-2}hr^{-1}$. Trends of daily means were shown in similar pattern, which NO emissions were increasing during late afternoon ($r^2$=0.04). These emission trends could be because soil temperature and moisture influence importantly soil microbiology.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.4
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• pp.160-164
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• 2008

Insulating and conducting 12CaO ${\cdot}7Al_2O_3$ (Cl2A7)-doped indium tin oxide (ITO) (ITO:Cl2A7 insulator and electride) thin films were deposited on glass substrates by an RF magnetron co-sputtering method with increasing number of insulating and conducting Cl2A7 target chips. The structural, electrical and optical properties of these films were investigated. The carrier concentration decreased and resistivity increased in the films with increasing number of Cl2A7 target chips. The optical transmittance of all of the thin films was above 80 % in the visible wavelength range. The structural property and surface roughness of the films were examined and the decrease of crystallinity and surface roughness was strongly dependent on the change of grain size.

• Analytical Science and Technology
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• v.24 no.4
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• pp.282-289
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• 2011

Rapid screening method for the determination of the emissions of pollutants from vehicle interior parts and materials have been developed as ISO 12219-2 which is using bag and based on a static condition. The method was not controlled humidity in the test bag, so it is not suitable test method for formaldehyde emission test which is highly related to humidity condition. In this study, possibility of control humidity in the static test bag by adding extra water and the effect of humidity condition for formaldehyde emissions have been investigated. The relative humidity in the test bag was affected not only amount of water added also material of test bag and test specimen. The emission intensity of formaldehyde was increased according to increasing relative humidity in test bag. But excessively supplied water was condensed on the inner surface of test bag and surface of sample specimen that were sorption formaldehyde and were reduced its emission intensity.

• Journal of Information Display
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• v.3 no.1
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• pp.17-21
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• 2002

Measurement of the ion-induced secondary electron emission coefficient (${\gamma}_i$) for insulating films is hampered by an unavoidable charging problem. Here, we demonstrate that a pulsed ion beam technique is a viable solution to the problem, allowing for accurate measurement of ${\gamma}_i$ for insulating materials. To test the feasibility of the pulsed ion beam method, the secondary electron emission coefficient from n-Si(100) is measured and compared with the result from the conventional continuous beam method. It is found that the ${\gamma}_i$ from n-Si(100) by the ion pulsed beam measured to be 0.34, which is the same as that obtained by continuous ion beam. However, for the 1000 A $SiO_2$ films thermally deposited on Si substrate, the measurement of ${\gamma}_i$ could be carred out by the pulsed ion method, even though the continuous beam method faced charging problem. Thus, the pulsed ion beam is regarded to be one of the most suitable methods for measuring secondary electron coefficient for the surface of insulator materials without experiencing charging problem. In this report, the dependence of ${\gamma}_i$ on the kinetic energy of $He^+$ is presented for 1000 ${\AA}$ $SiO_2$ films. And the secondary electron emission coefficient of 1000 ${\AA}$ MgO e-beam-evaporated on $SiO_2/Si$ is obtained using the pulsing method for $He^+$ and $Ar^+$ with energy ranging from 50 to 200 eV, and then compared with those from the conventional continuous method.

• Journal of the Korean institute of surface engineering
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• v.38 no.4
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• pp.163-166
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• 2005

Carbon nanotube-copper composite structures were fabricated using composite plating method and their field emission characteristics were investigated. Multi-walled carbon nanotubes (MWNTs) synthesized by chemical vapor deposition were used in the present study. It was revealed that turn-on field was about $3.0\;V/{\mu}m$ with the current density of $0.1\;{\mu}A/cm^2.$ We observed relatively uniform emission characteristics as well as stable emission current Carbon nanotube-copper composite plating method is efficient and it has no intrinsic limit on the deposition area. Moreover, it gives strong adhesion between emitters and an electrode. Therefore, we recommend that carbon nanotube-copper composite plating method can be applied to fabricate electron field emitters for large area FEDs and large area vacuum lighting sources.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.521-522
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• 2006

In this paper, hybrid air-water discharges were used to develop an optimal condition for providing a high level of water decomposition for hydrogen yield. Electrical and optical phenomena accompanying the discharges were investigated along with feeding gases, flow rates, and point-to-plane electrode gap distance. The primary focus of this experiment was put on the optical emission of the near UV range, with the energy threshold sufficient for water dissociation and excitation. The $OH(A^{2+},'=0\;X^2,"=0$) band's optical emission intensity indicated the presence of plasma chemical reactions involving hydrogen formation. In the gaseous atmosphere saturated with water vapor the OH(A-X) band intensity was relatively high compared to the liquid and transient phases although the optical emission strongly depended on the flow rate and type of feeding gas. In the gaseous phase discharge phenomenon for Ar carrier gas transformed into a gliding arc via the flow rate growth. OH(A-X) band's intensity increased according to the flow rate or residence time of He feeding gas. Reciprocal tendency was acquired for $N_2$ and Ar carrier gases. The peak value of OH(A-X) intensity was observed in the proximity of the water surface, however in the cases of Ar and $N_2$ with 0.5 SLM flow rate peaks shifted to the region below the water surface. Rotational temperature ($T_{rot}$) was estimated to be in the range of 900-3600 K, according to the carrier gas and flow rate, which corresponds to the arc-like-streamer discharge.