Seok-Gy Jeon

Korea Electrotechnology Research Institute-KERI, Busan, Busan, South Korea

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Publications (56)52.97 Total impact

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    ABSTRACT: We report novel two-dimensional (2D) shaped carbon nanotube (CNT) field emitters using triangular-shaped CNT film and its field emission properties. Using the 2D shaped CNT field emitters, we achieved excellent field emission performance with an extremely high emission current of 22 mA (equivalent to an emission current density >105 A/cm2) and excellent emission stability at 1 mA for 20 h. We also discuss the field emission behavior of the 2D shaped CNT field emitter in detail.
    Carbon 08/2015; 89:404-410. DOI:10.1016/j.carbon.2015.03.041 · 6.16 Impact Factor
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    ABSTRACT: A filtration-taping method was demonstrated to fabricate carbon nanotube (CNT) emitters. This method shows many good features, including high mechanical adhesion, good electrical contact, low temperature, organic-free, low cost, large size, and suitability for various CNT materials and substrates. These good features promise an advanced field emission performance with a turn-on field of 0.88 V/mm at a current density of 0.1 mA/cm2, a threshold field of 1.98 V/mm at a current density of 1 mA/cm2, and a good stability of over 20 h. The filtration-taping technique is an effective way to realize low-cost, large-size, and high-performance CNT emitters.
    Carbon letters 07/2014; 15(3):214-217. DOI:10.5714/CL.2014.15.3.214 · 1.63 Impact Factor
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    ABSTRACT: The carbon nanotube (CNT) field emitters have been fabricated by attaching a CNT film on a graphite rod using graphite adhesive material. The CNT field emitters showed much improved field emission properties due to increasing crystallinity and decreasing defects in CNTs after the high temperature thermal annealing at 900 °C in vacuum ambient. The CNT field emitters showed the low turn-on electric field of 1.15 V/μm, the low threshold electric field of 1.62 V/μm, and the high emission current of 5.9 mA which corresponds to a current density of 8.5 A/cm2. In addition, the CNT field emitters indicated the enhanced field emission properties due to the multi-stage effect when the length of the graphite rod increases. The CNT field emitter showed good field emission stability after the high temperature thermal annealing. The CNT field emitter revealed a focused electron beam spot without any focusing electrodes and also showed good field emission repeatability.
    AIP Advances 07/2014; 4(7):077110. DOI:10.1063/1.4889896 · 1.59 Impact Factor
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    ABSTRACT: Carbon nanotube (CNT) emitters with small emission area were fabricated on graphite rods using CNT films. By introducing the edge polishing process, the field emission performance of the CNT emitter was much improved, which showed a very high emission current of 6.34 mA (1.6 A/cm2) under an applied electric field of 5.3 V/μm. It also indicates good long-term emission stability, which reveals no degradation in the emission current for 20 h. The emission patterns demonstrate uniform and well-focused electron beam spots. The enhanced field emission performance is mainly attributed to the suppressed edge emission after the edge polishing process.
    Applied Physics Letters 01/2014; 104(4):043104-043104-5. DOI:10.1063/1.4863415 · 3.52 Impact Factor
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    ABSTRACT: Field emission properties of carbon nanotube (CNT) emitters dependent on electrode geometry have been systematically studied using two different types of diode electrode configurations. The experimental and simulation results clearly reveal that field emission properties, such as emission current and long-term emission stability, are strongly influenced by the geometry of the electrode configuration. The enhanced local electric field at the periphery of CNT emitters results in high local edge emissions that severely degrade emission current during long-term emission stability test and reduce the emission current density before electrical breakdown.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 09/2013; 31(5):052203-052203-5. DOI:10.1116/1.4818286 · 1.36 Impact Factor
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    ABSTRACT: We demonstrated field emission properties of a CNT point emitter fabricated by using CNTs on a graphite rod. The emitter has the highest current of 6.3 mA; the corresponding current density is 1.6 A/cm2. The emitter is stable at a current of 0.1 mA for 20 hours. It also showed a small and uniform emission pattern at the phosphor coated ITO glass. Our point emitter could be a good candidate for X-ray source applications.
    Vacuum Nanoelectronics Conference (IVNC), 2013 26th International; 01/2013
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    ABSTRACT: A micro-scale metal grid based on a silicon frame for application to electron field emission devices is introduced and experimentally demonstrated. A silicon lattice containing aperture holes with an area of 80 × 80 µm2 and a thickness of 10 µm is precisely manufactured by dry etching the silicon on one side of a double-polished silicon wafer and by wet etching the opposite side. Because a silicon lattice is more rigid than a pure metal lattice, a thin layer of Au/Ti deposited on the silicon lattice for voltage application can be more resistant to the geometric stress caused by the applied electric field. The micro-fabrication process, the images of the fabricated grid with 88% geometric transparency and the surface profile measurement after thermal feasibility testing up to 700 °C are presented.
    Journal of Micromechanics and Microengineering 10/2012; 22(10). DOI:10.1088/0960-1317/22/10/105009 · 1.73 Impact Factor
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    ABSTRACT: We investigate, using the 3-D particle-in-cell simulation code MAGIC, the millimeter-wavelength 20-vane magnetron operating at one of the spatial nonfundamental harmonics of the backward-traveling wave. This spatial harmonic is characterized by 16 (p = 16) RF electric field variations along the circumference of the magnetron interaction space (oscillation region). We call this magnetron as the “spatial-harmonic” magnetron operating in the “spatial-harmonic mode.” Calculated electron distribution reveals 16 electron spokes in the interaction space, which confirms the spatial-harmonic mode of the magnetron operation at p = 16. We observe a saturated output power of 3.2 kW, which corresponds to a power conversion efficiency of 12.3% when the applied voltage is 6.5 kV and the external magnetic field is 0.4 T. The operating frequency is 35.2 GHz. The collected anode current is 4 A when the current emitted from the cathode is 6.3 A. The dissipated power at each anode vane, depending on the anode vane position, is varied by the factor 1.8. The energy of back-bombarding electrons on the cathode increases from 305 to 503 eV while the spatial-harmonic magnetron operation is stabilized.
    IEEE Transactions on Plasma Science 08/2012; 40(8):1966-1971. DOI:10.1109/TPS.2012.2202693 · 0.95 Impact Factor
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    ABSTRACT: Continuous-wave (CW) terahertz (THz) imaging with a horn antenna is proposed to enhance the spatial resolution of a THz imaging system. The attached waveguide that is smaller than the wavelength can easily increase the spatial resolution, and the optimized horn flare can significantly increase the transmission power. Consequentially, transmission THz images of a phantom obtained by the amplitude signal using a 0.2 THz wave reveal that the spatial resolution is achieved up to 500 μm. Also, the transmitted power is increased up to 6 times higher compared to the pinhole aperture. The feasibility of CW THz imaging with a horn antenna is demonstrated by the inspection of the organic samples inside food resulting in a relatively high sensitivity for soft organic samples compared with the sensitivity of X-ray imaging to this kind of samples.
    Journal of infrared, millimeter and terahertz waves 06/2012; 33(6):657-664. DOI:10.1007/s10762-012-9902-1 · 1.89 Impact Factor
  • Dongwon Shin · Seok-Gy Jeon · Jung-Il Kim · Geun-Ju Kim · Min Sup Hur
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    ABSTRACT: We studied the influences of wide energy spectrum and emission angle of secondary electrons on electron bunching from a dc-biased single surface multipactor. In our previous study of the same system, an ideally narrow energy spread of secondary electrons without emission angle was used in the analysis of the electron trajectory [M. S. Hur, J.-I. Kim, G.-J. Kim, and S.-G. Jeon, Phys. Plasmas 18, 033103 (2011) and S.-G. Jeon, J.-I. Kim, S.-T. Han, S.-S. Jung, and J. U. Kim, Phys. Plasmas 16, 073101 (2009)]. In this paper, we investigated the cases with realistic energy spectrum, which is featured by a wide energy spread and significant emission angle. To theoretically approach the matter of emission angle, we employed a concept of effective longitudinal velocity distribution. The theoretical results are verified by particle-in-cell (PIC) simulations. We also studied the electron bunching from a copper by PIC simulations, where we observed stable electron bunches with bunch width of approximately 80 μm.
    Physics of Plasmas 02/2012; 19(2). DOI:10.1063/1.3685697 · 2.25 Impact Factor
  • Geun-Ju Kim · Jung-Il Kim · Seok-Gy Jeon · Jaehong Kim
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    ABSTRACT: In this paper, we studied THz tomography under continuous THz wave for material with permittivity of more than 2.
    Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2012 37th International Conference on; 01/2012
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    ABSTRACT: For application to electron field emission devices, a metal grid based on a silicon frame is introduced. Silicon frame is used to improve the thermal resistivity and electrical stability by electron beam. Silicon based micro-scale metal grid fabricated using MEMS technology.
    Vacuum Nanoelectronics Conference (IVNC), 2012 25th International; 01/2012
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    ABSTRACT: Research activities for development of a compact and high power terahertz radiation source using a CNT cold cathode are presented. Basic principles of the proposed device and experimental challenges to realize the device are discussed.
    Vacuum Nanoelectronics Conference (IVNC), 2012 25th International; 01/2012
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    ABSTRACT: A 0.1 THz 10 W clinotron is numerically and experimentally investigated for compact high-power terahertz radiation source. The output characteristics of the clinotron with the inclined sheet electron beam are examined by using the 3D particle-in-cell simulation code MAGIC and are compared with the measurements.
    Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 2012 37th International Conference on; 01/2012
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    Min Sup Hur · Dongwon Shin · Seok-Gy Jeon · Jung-Il Kim · Geun-Ju Kim
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    ABSTRACT: Generation of electron bunch from a dc-biased, single surface multipactor was studied theoretically and by PIC simulations. The condition for a spatially narrow bunch was obtained and verified by PIC simulations. This kind of multipactor is proposed to be used as a compact electron gun for various applications, such as linear accelerators.
    Vacuum Electronics Conference (IVEC), 2012 IEEE Thirteenth International; 01/2012
  • Jung-Il Kim · Seok-Gy Jeon · Geun-Ju Kim · Jaehong Kim
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    ABSTRACT: A terahertz (THz) Smith–Purcell (SP) backward-wave oscillator with an inverse wet-etched grating based on silicon has been proposed to enhance radiation intensity. This grating strengthens the interactions between an electron beam and the evanescent wave due to the adjacent surface structure between gratings that improves the magnitude of the electric field up to 1.7 times compared to the conventional rectangular gratings. A two-dimensional particle-in-cell (PIC) simulation shows that the radiated power is increased up to 2.3 times higher at the radiated frequency of 0.66 THz for an electron-beam energy of 30 keV.
    Physics Letters A 10/2011; 375(3-375):589-592. DOI:10.1016/j.physleta.2010.11.067 · 1.63 Impact Factor
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    Min Sup Hur · Jung-Il Kim · Geun-Ju Kim · Seok-Gy Jeon
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    ABSTRACT: The effects of the energy spread of secondary electrons are theoretically investigated for a dc-biased single-surface multipactor. In our previous publication [S. G. Jeon et al., Phys. Plasmas 16, 073101 (2009)], we obtained the conditions for the phase lock of an electron bunch, assuming zero velocity spread of the secondary electrons. In this work, we extended our previous theory to derive a quadratic map, by which the stability and bifurcation of the electron bunch can be systematically investigated. For the study of the energy spread of the secondary electrons, a randomized term was added to this map. The modified map then showed significant smearing-out of the bifurcated branches. The theoretical results were verified by particle-in-cell simulations, which showed good agreement in wide parameter ranges for both cases of monoenergetic and energy-spread secondary electrons.
    Physics of Plasmas 03/2011; 18(3). DOI:10.1063/1.3561786 · 2.25 Impact Factor
  • Geun-Ju Kim · Jung-Il Kim · Seok-Gy Jeon · Jaehong Kim
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    ABSTRACT: We suggest that THz wave is an alternative tool for the void detection in multilayer semiconductor. We measured the THz pulse using a reflective THz imaging system and obtained THz imaging by signal processing. And, to verify possibility of THz inspection, we compared with ultrasound.
    01/2011; DOI:10.1109/irmmw-THz.2011.6105023
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    ABSTRACT: A 35 GHz 3 kW spatial-harmonic magnetron employing 20-vane resonator is numerically and experimentally investigated. Simulated output power is 3.2 kW at beam voltage of 6.5 kV and anode current of 4 A using 3D PIC simulation. The measured resonant frequency for operation mode of p = 16 is 34.96 GHz.
    Infrared Millimeter and Terahertz Waves (IRMMW-THz), 2010 35th International Conference on; 10/2010
  • Seok-Gy Jeon · Jung-Il Kim · Geun-Ju Kim
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    ABSTRACT: We report a reflex klystron in which an embedded planar cold cathode is used to generate a secondary electron beam. By using secondary electron cathode with a high secondary electron yield, the number of secondary electrons can be sufficiently increased and adjusted to activate the reflex klystron. In our three-dimensional particle-in-cell simulations, oscillation of the device was demonstrated at 100 GHz when using a secondary electron cathode with a maximum yield of 20 while a. primary electron beam with a current density less than 5 A/cm(2) was irradiated to create secondary electrons. The current density of the primary electron beam is achievable with typical field emission cathodes if they are equipped with an electron beam focusing lens, and a maximum yield of 20 can be obtained if magnesium oxide is used for the secondary electron emission.
    Journal- Korean Physical Society 09/2010; 57(3). DOI:10.3938/jkps.57.489 · 0.43 Impact Factor