• Title/Summary/Keyword: field emission characteristics

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Effect of Rapid Thermal Annealing on Growth and Field Emission Characteristics of Carbon Nanotubes

  • Ko, Sung-Woo;Shin, Hyung-Cheol;Park, Byung-Gook;Lee, Jong-Duk;Jun, Pil-Goo;Kwak, Byung-Hwak;Noh, Hyung-Wook;Uh, Hyung-Soo
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.453-455
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    • 2004
  • The effect of rapid thermal annealing (RTA) treatment on the growth characteristics of CNTs was investigated. We observed that Ni catalyst film was agglomerated by RTA treatment, resulting in the formation of Ni nanoparticles. The well aligned CNTs were grown from the Ni nanoparticles by plasma enhanced chemical vapor deposition (PECVD). It is shown that the size and distribution of the nanoparticles depend mainly on the annealing temperature and initial thickness of the metal layer. Also, it was found that CNTs grown through optimal RTA treatment had the more improved field emission characteristics than those of as-grown CNTs.

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Characteristics of Magnetic Resonance-Based Attenuation Correction Map on Phantom Study in Positron Emission Tomography/Magnetic Resonance Imaging System

  • Hong, Cheolpyo
    • Progress in Medical Physics
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    • v.31 no.4
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    • pp.189-193
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    • 2020
  • An MR-based attenuation correction (MRAC) map plays an important role in quantitative positron emission tomography (PET) image evaluation in PET/magnetic resonance imaging (MRI) systems. However, the MRAC map is affected by the magnetic field inhomogeneity of MRIs. This study aims to evaluate the characteristics of MRAC maps of physical phantoms on PET/MRI images. Phantom measurements were performed using the Siemens Biograph mMR. The modular type physical phantoms that provide assembly versatility for phantom construction were scanned in a four-channel Body Matrix coil. The MRAC map was generated using the two-point Dixon-based segmentation method for whole-body imaging. The modular phantoms were scanned in compact and non-compact assembly configurations. In addition, the phantoms were scanned repeatedly to generate MRAC maps. The acquired MRAC maps show differently assigned values for void areas. An incorrect assignment of a void area was shown on a locally compact space between phantoms. The assigned MRAC values were distorted using a wide field-of-view (FOV). The MRAC values also differed after repeated scans. However, the erroneous MRAC values appeared outside of phantom, except for a large FOV. The MRAC map of the phantom was affected by phantom configuration and the number of scans. A quantitative study using a phantom in a PET/MRI system should be performed after evaluation of the MRAC map characteristics.

Field Emission Properties of Multiwalled Carbon Nanotubes Synthesized by Pin-to-Plate Type Atmospheric Pressure Plasma Enhanced Chemical Vapor Deposition (Pin-to-plate Type 대기압 PECVD 방법을 이용해 성장된 다중벽 탄소나노튜브의 전계방출 특성연구)

  • Park Jae-Beom;Kyung Se-Jin;Yeom Geun-Young
    • Journal of the Korean Vacuum Society
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    • v.15 no.4
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    • pp.374-379
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    • 2006
  • In this study, carbon nanotubes (CNTs) were grown on glass substrates coated with Ni/Cr by an atmospheric pressure plasma enhanced chemical vapor deposition(AP-PECVD) and their structural and electrical characteristics were investigated as a possible application to the field emitter of field emission display (FED) devices. The substrate temperature ($400{\sim}500^{\circ}C$) were varied and the grown CNTs were multi wall CNTs (at $500^{\circ}C$, 15 - 20 layers of graphene sheets, distance of each layer : 0.3nm, inner diameter: 10 - 15nm, outer diameter: 30 - 40nm). The ratio of defective carbon peak to graphite carbon peak of the CNTs grown at $500^{\circ}C$ (C measured by fourier transform(FT)-Raman was 0.772 $I_D / I_G$ ratio. When field emission properties were measured, the turn-on field was $2.92V/{\mu}m$ and the emission field at $1mA/cm^2$ was $5.325V /{\mu}m$.

Electrical Characteristics of Flat Cesium Antimonide Photocathode Emitters in Panel Devices

  • Jeong, Hyo-Soo
    • Transactions on Electrical and Electronic Materials
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    • v.17 no.5
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    • pp.306-309
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    • 2016
  • The Cs3Sb photocathode was formed by non-vacuum process technology. An in-situ vacuum device was fabricated successively with flat cesium antimonide photocathode emitters fabricated in a process chamber. The electrical properties of the device were characterized. Electron emission from the devices was induced by photoemitted electrons, which were accelerated by an anode electric field that was shielded from the photoemitter surface. The electrical characteristics of the devices were investigated by measuring the anode current as a function of device operation times with respect to applied anode voltages. Planar blue LED light with a 450 nm wavelength was used as an excitation source. The results showed that the cesium antimonide photocathode emitter has the potential of long lifetime with stable electron emission characteristics in panel devices. These features demonstrate that the cesium antimony photocathodes produced by non-vacuum processing technology is suitable for flat cathodes in panel device applications.

Fabrication of Carbon Nanotube Field Emitters

  • Yoon, Hyeun-Joong;Jeong, Dae-Jung;Jun, Do-Han;Yang, Sang-Sik
    • Journal of Electrical Engineering and Technology
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    • v.3 no.1
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    • pp.121-124
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    • 2008
  • This paper presents the fabrication and field emission of carbon nanotube field emitters for a micro mass spectrometer. The carbon nanotube is an adequate material as a field emitter since it has good characteristics. We have successfully fabricated a diode field emitter and a triode field emitter. Each field emitter has been constructed using several micromachining processes and a thermal CVD process. In the case of the diode field emitter, to increase the electric field, the carbon nanotubes are selectively grown on the patterned nickel catalyst layer. The electron current of the diode field emitter is 73.2 ${\mu}A$ when the anode voltage is 1100V. That of the triode field emitter is 3.4 pA when the anode voltage is 1000V.

Analysis of Environment Emission Characteristics Each Construction Type for Road Field (국도건설공사 도로분야의 공종별 환경부하량 특성분석)

  • Kim, Sang-Ryong;Lee, Dong-Eun;Kim, Byung-Soo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.37 no.1
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    • pp.143-151
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    • 2017
  • Recently Korea has presented carbon emission reduce goal of 37% compare to BAU until 2030 according to Paris Agreement in order to correspond to climate change. For this, researchers need to study positively on construction industry that emit $CO_2$ of $3^{rd}$ volume of 28 industry classification. This study calculated environmental load by LCA using the road part except tunnel and bridge among national road cases completed already. After selecting representative type of large construction type based on environmental emission, earth works, drainage works and paving works took up 84%. And this study analyzed the environmental emission feature of each detail construction type after selecting representative type each detail construction type. Utilization of each construction type emission attribute to environmental load during national road construction, will be helpful in making decision of eco-friendly national road construction based on environmental emission.

Measurement Uncertainty of Nitrous Oxide Concentrations from a Upland Soil Measured by an Automated Open Closed Chamber Method (밭토양에서 폐쇄형 자동 챔버법으로 측정한 아산화질소 농도에 대한 측정 불확도)

  • Ju, Ok Jung;Kang, Namgoo;Lim, Gap June
    • Korean Journal of Environmental Agriculture
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    • v.39 no.3
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    • pp.237-245
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    • 2020
  • BACKGROUND: The closed chamber method is the most commonly used for measuring greenhouse gas emissions from upland fields. This method has the advantages of being simple, easily available and economical. However, uncertainty estimation is essential for accurate assessment of greenhouse gas emissions and verification of emission reductions. The nitrous oxide emissions from upland field is very important for the nitrogen budget in the agriculture sectors. Although assessment of uncertainty components affecting nitrous oxide emission from upland field is necessary to take account of dispersion characteristics, research on these uncertainty components is very rare to date. This study aims at elucidation of influencing factors on measurement uncertainty of nitrous oxide concentrations measured by an automated open closed chamber method from upland field. METHODS AND RESULTS: The nitrous oxide sampling system is located in the upland field in Gyeonggi-do Agricultural Research and Extension Services (37°13'22"N, 127°02'22"E). The primary measurement uncertainty components influencing nitrous oxide concentrations (influencing factors) investigated in this research are repeatability, reproducibility and calibration in the aspects of nitrous oxide sampling and analytical instrumentation. The magnitudes of the relative standard uncertainty of each influencing factor are quantified and compared. CONCLUSION: Results of this study show what influencing factors are more important in determination of nitrous oxide concentrations measured using the automated open closed chambers located in the monitoring site. Quantifying the measurement uncertainty of the nitrous oxide concentrations in this study would contribute to improving measurement quality of nitrous oxide fluxes.

A Study on Estimating PM Emission from Asphalt-Concrete Manufacturing Facilities (아스콘 제조 시설에서의 먼지 배출량 산정 방안 연구)

  • Jang, Kee-Won;Lee, Sang-Bo;Kim, Jong-Hyeon;Kim, Hyoung-Chun;Hong, Ji-Hyung;Kim, Sang-Kyun
    • Journal of Korean Society for Atmospheric Environment
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    • v.30 no.1
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    • pp.37-47
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    • 2014
  • In this study, field measurement was carried out for reasonable improvement of asphalt concrete manufacturing facilities' PM emissions estimation method. Through those, this study calculated PM emission factor and tried to estimate PM emissions from asphalt concrete manufacturing facilities suitable for domestic characteristics. As a result, the efficiency of the PM control device was measured as 99.9%. Using this, uncontrolled PM emission factor was calculated. PM emission factor was calculated 10.97 kg/ton at 23 asphalt concrete manufacturing facilities of 22 workplaces. The PM current emission factor of the US Environment Protection Agency (EPA) is 14.4 kg/ton, the factor calculated from this study is about 24% lower than the EPA standard.

Luminous Characteristics of Transparent Field Emitters Produced by Using Ultra-thin Films of Single Walled Carbon Nanotubes

  • Jang, Eun-Soo;Goak, Jeung-Choon;Lee, Han-Sung;Lee, Seung-Ho;Lee, Nae-Sung
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2009.05a
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    • pp.31.1-31.1
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    • 2009
  • Carbon nanotubes (CNTs) are attractive material because of their superior electrical, mechanical, and chemical properties. Furthermore, their geometric features such as a large aspect ratio and a small radius of curvature at tip make them ideal for low-voltage field emission devices including backlight units of liquid crystal display, lighting lamps, X-ray source, microwave amplifiers, electron microscopes, etc. In field emission devices for display applications, the phosphor anode is positioned against the CNT emitters. In most case, light generated from the phosphor by electron bombardment passes through the anode front plate to reach observers. However, light is produced in a narrow depth of the surface of the phosphor layer because phosphor particles are big as much as several micrometers, which means that it is necessary to transmit through the phosphor layer. Hence, a drop of light intensity is unavoidable during this process. In this study, we fabricated a transparent cathode back plate by depositing an ultra-thin film of single walled CNTs (SWCNTs) on an indium tin oxide (ITO)-coated glass substrate. Two types of phosphor anode plates were employed to our transparent cathode back plate: One is an ITO glass substrate with a phosphor layer and the other is a Cr-coated glass substrate with phosphor layer. For the former case, light was radiated from both the front and the back sides, where luminance on the back was ~30% higher than that on the front in our experiments. For the other case, however, light was emitted only from the cathode back side as the Cr layer on the anode glass rolled as a reflecting mirror, improving the light luminance as much as ~60% compared with that on the front of one. This study seems to be discussed about 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 cathode back side. The experimental procedures are as follows. First, a CNT aqueous solution was prepared by ultrasonically dispersing purified SWCNTs in deionized water with sodium dodecyl sulfate (SDS). A milliliter or even several tens of micro-liters of CNT solution was deposited onto a porous alumina membrane through vacuum filtration. Thereafter, the alumina membrane was solvated with the 3 M NaOH solution and the floating CNT film was easily transferred to an ITO glass substrate. It is required for CNT film to make standing CNTs up to serve as electron emitter through an adhesive roller activation.

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Preparation of uniformly dispersed iron nanoparticles and growth of carbon nanotube

  • Kim, Do-Yoon;Yoo, Ji-Beom;Berdinsky, A.S.;Park, Chong-Yun;Han, In-Taek;Jung, Jae-Eun;Jin, Yong-Wan;Kim, Jong-Min
    • 한국정보디스플레이학회:학술대회논문집
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    • 2004.08a
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    • pp.462-464
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    • 2004
  • We studied the growth characteristics of carbon nanotubes which was grown from uniformly dispersed iron nanoparticles prepared from iron-acetate [Fe(II)$(CH_3COO)_2$]. The density of CNT was controlled from precursor concentrations. We also investigated the field emission properties of CNTs. We found that the optimization of CNT density is an important factor for field_emission properties.

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