• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.202-202
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• 2000

AC-PDP(Plasma Display Paner)는 기체 방전을 이용한 디스플레이로서 기체에 직접 노출되는 MgO 보호막의 2차전자 방출계수(${\gamma}$는 AC-PDP의 방전특성을 결정짓는 중요한 요소이다. MgO 보호막의 이차전자 방출계수는 AC-PDP에 주입하는 기체의 종류, 결정 방향성과 표면오염상태 등에 영향을 받는다. 본 연구에서는 유리 기판위에 Al 전극을 증착, 에칭후 screen printing으로 유전체를 도포, 소성 한 21inch 규격의 test panel에 MgO 보호막을 E-Beam으로 5000$\AA$ 증착한 후 MgO 보호막을 대기에 노출되는 시간간격을 변수로 하여 대기 열처리 한 MgO보호막의 2차 전자방출계수를 ${\gamma}$-FIB(Focused Ion Beam) 장치를 이용하여 측정하였다. 그리고 대기 노출 간격은 1분, 5분, 20분으로 하여 2차 전자방출계수를 측정하였고, 2차전자방출계수 측정 시 가속전압은 50V에서 200V까지 변화를 주었으며, Ne+을 사용하여 1.2$\times$10-4Torr의 진공도를 유지하며 측정하였다. 또한 각각의 MgO막의 에너지 갭을 광학적 방법을 이용하여 구하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.4
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• pp.145-150
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• 2007

The $SiO_2$ and $TiO_2$ thin films for the multilayer interference filter application were manufactured by electron beam process. In case of electron beam process with ion source, the anode current was controlled by gas volume ratio of $O_2$ and Ar. Substrate temperature of electron beam deposition without ion source was increased from 100 to $250^{\circ}C$ with $50^{\circ}C$ increment. The surface roughness values of $SiO_2$ thin films was most low value at $200^{\circ}C$ substrate temperature and 0.2 A anode current respectively. And the surface roughness values of $TiO_2$ thin films was most low value at room temperature and 0.2 A anode current repectively. The refractive index of $SiO_2$ and $TiO_2$ thin films to be deposited with ion source was usually lower than that of thin films without ion source.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.10
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• pp.1541-1548
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• 2004

A nano-stage simulation tool is developed for an advanced E-beam lithography system. Even if piezo-actuators are believed to be compatible fer the E-beam lithograpy system it is difficult to predict their characteristics due to their nonlinearities such as hysteresis and creep. In this paper, the nonlinear properties are modeled for a piezo-actuator by considering the voltage range and speed variations. The hysteresis is described as the first order differential equation with 24 sets of parameters and the creep is modeled as a time-dependent logarithmic function with 2 sets of a parameter. A two-axis nano stage with piezo-actuators are investigated for realizing nano scale motions. The characteristics of flexure guide mechanisms are analyzed based on the finite element method using the ANSYS software. The simulation tool for the nano stage is constructed by using the RecurDyn software. The dynamic response of the nano stage is obtained in simulations and compared with the experimental data.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.286-286
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• 2011

현재의 NEDO (New Energy and industrial technology Development Organization) style Si 정련은 두 단계로 구분되어 있다. 고출력 집속 전자빔을 이용한 금속 실리콘의 1차 용융과 대기압 근처의 플라즈마 아크 용해를 이용해서 B, P를 약간의 반응성 가스를 첨가 하여 제거하는 방법이다. 그러나 저가형 실리콘을 생산하려는 취지와 달리 두 가지의 고가 장비가 필요하다. E-beam melting 장치에서도 반응성이 높은 라디칼을 생성할 수 있다면 하나의 장비에서 두 가지의 정련 작업을 진행시킬 수 있다. 본 연구에서는 고진공에서(< 10-4 Torr) 동작하는 E-beam의 성능에 전혀 영향을 주지 않으면서 플라즈마를 용이하게 생성 시킬 수 있는 방법을 개발하고 이를 적용하여 실제 금속 순도 실리콘 내에 존재하는 B, P가 제거되는지 확인하는 것을 연구 내용으로 한다. 본 연구는 MG (Metal Grade) - Si 을 플라즈마 보조 전자빔 정련을 이용하여 정련한 Si 의 불순물 함량의 개선 효과를 조사하는 것이다. MG-Si 의 정련 방법 중에서 고출력 집속 전자빔을 이용하여 휘발성 오염물질을 제거 후, 플라즈마 아크 용해를 이용해서 B 를 제거하는 방법을 접목시켰다. MG-Si 에 DC power 와 전자빔을 집속시켜서 정련을 하면 챔버 내의 잔류 수증기가 플라즈마에 의해 분해되어 O를 생성하고, B와 반응을 하여 BO 형태로 제거가 된다. 방전 전압 700 V 와 전자빔 가속 전압이 4.5 kV, 방출 전류는 11 A, 진공 챔버 내의 압력은 $7.2{\times}10^{-4}$ Torr에서 정련을 진행하여 B를 제거했다.

• Progress in Medical Physics
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• v.10 no.1
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• pp.17-22
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• 1999

INJ-I, INJ-E, PFN, BMI, and PRF were selected among the various factors which constitute a digital linear accelerator to find effects on the dose distribution by changing current and voltage within the permitted scale which Mevatron automatically maintained. We measured the absorbed dose using an ion chamber, analyzed the waveform of beam output using an oscilloscope, and measured symmetry and flatness using a dosimetry system. An RFA plus (Scanditronix, Sweden) device was used as a dosimetry system. Then an 0.6cc ion chamber (PR06C, USA), an electrometer (Capintec192, USA), and an oscilloscope (Tektronix, USA) were employed to measure the changes on the dose distribution characteristics by changing the beam-tuning parameters. When the currents and the voltages of INJ-I, INJ-E, PFN, BMI, and PRF were modified, we were able to see the notable change on the dose rate by examining the change of the output pulse using the oscilloscope and by measuring them using the ion chamber. However, the results of energy and flatness graph from RF A plus were almost identical. The factors had fine differences: INJ-I, INJ-E, PFN, BMI, and PRF had 0.01∼0.02% differences in D10/D20, 0.1∼0.2 % differences in symmetry, and 0.1∼0.4% differences in flatness. Since Mevatron controlled itself automatically to keep the reference value of the factor, it was not able to see large differences in the dose distribution. There were fine differences on the dose rate distribution when the voltage and the currents of the digitized factors were modified Nonetheless, a basic operational management information was achieved.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.128-138
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• 2022

In this study, in order to apply ultra-high-strength concrete beams of 100 MPa or more manufactured by centrifugal molding as the superstructure of the avalanche tunnel, the purpose is to verify the structural safety of the corner rigid joint in which the centrifugal molded beam is integrated with the substructure, which is the negative moment area. A full-size specimen was manufactured, and loading tests and analysis studies were performed. In order to expect the same effect that the maximum moment occurs in the corner joint part of the upper slab end when the standard model of the avalanche tunnel is designed with a load combination according to the specification, a modified cantilever type structural model specimen was manufactured and the corner rigid joint was fixedly connected. A study was performed to determine the performance of the method and the optimal connection construction method. The test results demonstrated that the proposed connection system outperforms others. Despite having differences in joint connection construction type, stable flexural behavior was shown in all the tested specimens. The proposed method also outperformed the behavior of centrifugally formed beams and upper slabs. The behavior of the corner rigid joint analysis model according to the F.E. analysis showed slightly greater stiffness compared to the results of the experiment, but the overall behavior was almost similar. Therefore, there is no structural problem in the construction of the corner rigid joint between the centrifugally formed beam and the wall developed in this study.

• Progress in Medical Physics
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• v.18 no.2
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• pp.87-92
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• 2007

A thermal neutron beam facility utilizing a typical tangential beam port for Neutron Capture Therapy was installed at the HANARO, 30 MW multi-purpose research reactor. Mixed beams with different physical characteristics and relative biological effectiveness would be emitted from the BNCT irradiation facility, so a quantitative analysis of each component of the mixed beams should be performed to determine the accurate delivered dose. Thus, various techniques were applied including the use of activation foils, TLDs and ionization chambers. All the dose measurements were perform ed with the water phantom filled with distilled water. The results of the measurement were compared with MCNP4B calculation. The thermal neutron fluxes were $1.02E9n/cm^2{\cdot}s\;and\;6.07E8n/cm^2{\cdot}s$ at 10 and 20 mm depth respectively, and the fast neutron dose rate was insignificant as 0.11 Gy/hr at 10 mm depth in water The gamma-ray dose rate was 5.10 Gy/hr at 20 mm depth in water Good agreement within 5%, has been obtained between the measured dose and the calculated dose using MCNP for neutron and gamma component and discrepancy with 14% for fast neutron flux Considering the difficulty of neutron detection, the current study support the reliability of these results and confirmed the suitability of the thermal neutron beam as a dosimetric data for BNCT clinical trials.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.446-451
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• 2001

We made a laser induced grating spectrometer(LIGS) and measured the thermal grating signal generated in a $C_3$ $H_{8}$ flame. The thermal grating was formed in the C7Ha flame with two second-harmonic Nd:YAG pulse laser beams, and an LIGS signal was generated by Bragg scattering of a probe laser beam A $r^+.laser(488 nm). We found the modulation period of the signal depends linearly on the spacing of the grating set in the flame. We determined flame temperature by fitting the modulated signal and soot concentration with signal strength. Using this technique, we also obtained temperature profile and soot-particle distribution in a $C_3$ $H_{8}$ flame .e .

• Korean Journal of Materials Research
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• v.7 no.3
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• pp.213-217
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• 1997

AOhf(Hcousto-r)l)tic niodulator) with :!OOlIiz freclucncl- and Sfi(;(Seconrl harmonic generation) green lasel-Lvith 53% nm wavelength were used for Il\'IIII~Dii.it,ii v~ilco disk recorder) FOI rhe appli~aptin of high densit]. optical recording, a high po\ver I ~ c r is r c ~ ~ l i ~ i l - u l ic I !tic. s\-sti,m a n d optic.,~I io;iting l,t)c>rs of each optical device must have a high laser damage threshoid hie rn;itie ant] retlwtive coatings on a $TeO_{2}$ singlc crystal. which is used as an acoustooptic material, by E-beam evaporation method. Laser damage threshold \vas nicdsureci hy Ar laser with the input power oi 0.55LV 1,aser damage threiholti 01 $ZrO_{2}$ and $SiO_{2}$. filn-is were higher than $AI_{2}O_{3}$ f i l m U'e also investigated a long--tern1 stability of the output po\ver of St{(; green laser

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.451-451
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• 2013

현재 세계적으로 에너지 공급원의 다변화가 시급한 실정이며 그 후보로 태양에너지, 풍력 및 수력에너지와 같은 신재생 에너지에 대한 연구분야가 부각되고 있다. 전체 에너지 중 신재생 에너지의 비중은 빠르게 증가되고 있으며, 그 중에서도 태양광에너지의 분야가 가장 활발히 연구되고 있다. 특히, III-V족 화합물 반도체 태양전지는 직접 천이형 밴드갭을 가지고 있어 기존 실리콘 태양전지에 비해 광 흡수율이 높은 장점을 가지고 있다. 따라서 본 연구에서는 Molecular Beam Epitaxy (MBE)장치를 이용하여 성장온도에 따른 p-n접합 GaAs 태양전지 구조를 제작하여, 광전변환 효율과 결함구조 관련성을 조사하였다. 먼저 Si이 $1{\times}10^{18}cm^{-3}$으로 도핑된 n형 GaAs기판위에 성장온도 $480^{\circ}C$와 $590^{\circ}C$에서 Be을 $5{\times}10^{18}cm^{-3}$ 도핑한 p 형 GaAs를 200 nm 두께로 각각 성장하여, 2개의 p-n 접합 GaAs 태양전지 구조를 제작하였다. 시료의 전기적 특성과 결함상태는 Capacitance-Voltage (C-V) 와 Deep Level Transient Spectroscopy (DLTS)를 사용하여 조사하였다. DLTS 측정을 위해 p-형의 GaAs박막 위에 Au(300 nm)/Pt(30 nm)/Ti(30 nm)를 e-beam evaporator로 증착한 후, 직경 $300{\mu}m$의 메사 에칭으로 p-n접합 다이오드 구조를 제작하였다. 본 연구를 통해 GaAs p-n접합구조 성장온도에 따른 광전변환 효율과 결함상태와의 물리적인 연관성을 논의할 것이다.