• Proceedings of the KIEE Conference
• /
• 1995.07a
• /
• pp.18-20
• /
• 1995

This paper describes a 7.5T magnetic flux density superconducting wiggler that minimize net angular deflection and displacement of an electron rotating along the orbit at storage ring in Pohang Light Source. It consist of dipole superconducting magnet,high uniformity flux distribution due to current source supply,cryostat,vacuum chamber,measurement system. In this paper magnet design procedure, manufacturing, experimental results are contained.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.1288-1293
• /
• 2007

The present study covers the design and analysis of a thermionic scanning electron microscope (SEM) column. The SEM column contains an electron optical system in which electrons are emitted and moved to form a focused beam, and this generates secondary electrons from the specimen surfaces, eventually making an image. The electron optical system mainly consists of a thermionic electron gun as the beam source, the lens system, the electron control unit, and the vacuum unit. In the design process, the dimension and capacity of the SEM components need to be optimally determined with the aid of finite element analyses. Considering the geometry of the filament, a three-dimensional (3D) finite element analysis is utilized. Through the analysis, the beam emission characteristics and relevant trajectories are predicted from which a systematic design of the electron optical system is enabled. The validity of the proposed 3D analysis is also discussed by comparing the directional beam spot radius. As a result, a prototype of a thermionic SEM is successfully developed with a relatively short time and low investment costs, which proves the adoptability of the proposed 3D analysis.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.50 no.6
• /
• pp.281-287
• /
• 2001

In order to obtain guidelines for design and operation of a new plasma source by a magnetic neutral loop discharge(NLD), the electron behavior was studied experimentally and numerically. Experimentally, the magnetic field gradient was changed over a wide range, and it was found that there existed an optimum value for efficient plasma production. Analyses of the electron behavior were performed using a model that included effects of a three dimensional electromagnetic field configuration considering the spatial decay of the electric field, and the limitation to the motion of electron caused by the existence of walls and thus electron loss at wall surfaces. These three dimensional factors were found to explain the existence of the optimum magnetic field gradient. It was shown that the L dependence of the plasma production efficiency was firstly decided by the finite decay length of the electric field strength, which was further modified by electron elastic collisions with neutral atoms which drove the electron to walls. The latter effect tends to reduce the optimum value of L.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2004.04a
• /
• pp.494-499
• /
• 2004

A ion source using inductively coupled plasma has been tested in order to test its feasibility as a high brightness ion source for focused ion beam. When operating the ion source with filter magentas in front of plasma electrode for a negative ion source, lower remittances are expected. Extracted beam remittances are measured with an Allison-type scanning device for various plasma parameters and extraction conditions. The normalized omittance has been measured to be around 0.2$\pi$mmmrad with beam currents of up to 0.55 ㎃. In particular, noting that multicusp magnets have a role in decreasing the remittance as well as increasing plasma discharge efficiency, transverse magnetic field has been confirmed to be a useful tool fur decreasing remittance via electron energy control.

• Proceedings of the KIEE Conference
• /
• 2001.07c
• /
• pp.1357-1359
• /
• 2001

0.2${\mu}m$ 이하의 최소 선폭을 가지는 소자를 구현할 때 drain induced barrier lowering (DIBL)이나 hot electron effect와 같은 short channel effect (SCE)가 나타나며 이로 인하여 소자의 신뢰성이 악화되기도 한다. 이를 개선하기 위한 방법 중 하나가 silicon selective epitaxial growth (SEG)를 이용한 elevated source/drain (ESD) 구조이다. 본 연 구에서는 silicon selective epitaxial growth를 이용하여 elevated source/drain 구조를 갖는 MOSFET 소자와 일반적인 MOSFET 구조를 갖는 소자와의 차이를 elevated source/drain의 높이 변화에 따른 전류 전압 특성을 이용하여 비교, 분석하였으며 그 결과 elevated source/drain 구조가 short channel effect를 감소시킴을 확인할 수 있었다.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.48 no.9
• /
• pp.605-610
• /
• 1999

An SOI(Silicon-On-Insulator) LD(Lateral Double-diffused)MOS with a recessed source structure is proposed to improve the on-resistance and the breakdown voltage. The recessed source structure can decrease the on-resistance by reducing the path of electron current, also increase the breakdown voltage by extending the effective length of gate field plate. Simulation results by TSUPREM4 and MEDICI have shown that the on-resistance of the LDMOS with a recessed source was 26% lower than conventional LDMOS. The breakdown voltage of proposed device was found to be 45V while that of conventional device was 36.5 V. At the same breakdown voltage of 36.5V, the on-resistance of the LDMOS with a recessed source was 41% lower than that of conventional structure.

• Environmental Engineering Research
• /
• v.16 no.4
• /
• pp.213-218
• /
• 2011

The two-stage intermittent aeration activated sludge process (IAP) and dynamic-flow intermittent aeration activated sludge process (DFP) were investigated for the nutrient removal of domestic wastewater. Three sets of IAP and one set of DFP were operated. The fermented settled sludge taken from the primary settling tank was added to two IAP and one DFP as an external electron donor, with one IAP, in which an external carbon source was not added, as a control. All the systems were operated at a sludge retention time of 20 days and a hydraulic retention time of 12 hr. A Higher denitrification rate was observed with the fermented settled sludge for the denitrification compared to the process without the addition of the organic source. The result indicates that the fermented acid from the primary domestic sludge has been proved to be an excellent electron donor for denitrification and biological phosphorus removal with IAP and DFP in treating relatively low C/N ratio(Carbon / Nitrogen ratio) wastewater. Phosphate accumulating organisms have a capability of competing with denitrifiers in the presence of volatile organic acids under anoxic conditions.

• Applied Science and Convergence Technology
• /
• v.27 no.5
• /
• pp.90-94
• /
• 2018

The electron band structure of manganese-adsorbed graphene on an SiC(0001) substrate has been studied using angle-resolved photoemission spectroscopy. Upon introducing manganese atoms, the conduction band of graphene, that is observed in pristine graphene indicating intrinsic electron-doping by the substrate, completely disappears and the valence band maximum is observed at 0.4 eV below Fermi energy. At the same time, the slope of the valence band decreases by the presence of manganese atoms, approaching the electron band structure calculated using the local density approximation method. The former provides experimental evidence of the formation of nearly free-standing graphene on an SiC substrate, concomitant with a metal-to-insulator transition. The latter suggests that its electronic correlations are efficiently screened, suggesting that the dielectric property of the substrate is modified by manganese atoms and indicating that electronic correlations in grpahene can also be tuned by foreign atoms. These results pave the way for promising device application using graphene that is semiconducting and charge neutral.

• Korean Journal of Materials Research
• /
• v.23 no.9
• /
• pp.517-524
• /
• 2013

The electrical and optical properties of fluorine-doped tin oxide films grown on polyethylene terephthalate film with a hardness of 3 using electron cyclotron resonance plasma with linear microwave of 2.45 GHz of high ionization energy were investigated. Fluorine-doped tin oxide films with a magnetic field of 875 Gauss and the highest resistance uniformity were obtained. In particular, the magnetic field could be controlled by varying the distribution in electron cyclotron deposition positions. The films were deposited at various gas flow rates of hydrogen and carrier gas of an organometallic source. The surface morphology, electrical resistivity, transmittance, and color in the visible range of the deposited film were examined using SEM, a four-point probe instrument, and a spectrophotometer. The electromagnetic field for electron cyclotron resonance condition was uniformly formed in at a position 16 cm from the center along the Z-axis. The plasma spatial distribution of magnetic current on the roll substrate surface in the film was considerably affected by the electron cyclotron systems. The relative resistance uniformity of electrical properties was obtained in film prepared with a magnetic field in the current range of 180~200A. SEM images showing the surface morphologies of a film deposited on PET with a width of 50 cm revealed that the grains were uniformly distributed with sizes in the range of 2~7 nm. In our experimental range, the electrical resistivity of film was able to observe from $1.0{\times}10^{-2}$ to $1.0{\times}10^{-1}{\Omega}cm$ where optical transmittance at 550 nm was 87~89 %. These properties were depended on the flow rate of the gas, hydrogen and carrier gas of the organometallic source, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.12 no.3
• /
• pp.1319-1326
• /
• 2011

We have investigated the characteristics of the electron beam (e-beam) in the miniaturized free electron laser module by using the commercial 3D simulation tool OPERA. The e-beam was made parallel before entering the slit-type wiggler by the negative bias applied to the central electrode of the electron lens. With respect to the different structures of the wiggler, we obtained the inner distributions of the electrical potential and the electric field, which was, in turn, used to calculate the trajectory of the e-beam in the wiggler.