• Electrical & Electronic Materials
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• v.8 no.4
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• pp.426-433
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• 1995

Effect of boron in GaAs have been investigated by photo induced current transient spectroscopy(PICTS). The starting material was undoped liquid encapsulated Czochralski(LEC) semi insulating GaAs and boron ion implantation at 150keV energy was conducted with dose of 10$\^$12/ and 10$\^$13/ions/cm$\^$2/. In ion implanted samples, the peaks related arsenic vacancy(V$\_$As/) were decreased but complex lattice defect was increased with annealing temperature. U band was observed at ion implanted(10$\^$13/ ions/cm$\^$2/) and thermally treated(550.deg. C) sample. More negative peak was detected after annealing at temperature between 600 and 700.deg. C. The measurement of dark current showed that the formation of B$\_$GA/-V$\_$As/, complex defect and complex lattice defect by ion implantation were a reasonable explanation for the decrease in dark current.

• Bulletin of the Korean Chemical Society
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• v.34 no.12
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• pp.3659-3664
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• 2013

Eight representative explosives (ammonium perchlorate (AP), ammonium nitrate (AN), trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), cyclonite (RDX), cyclotetramethylenetetranitramine (HMX), pentaerythritol tetranitrate (PETN), and hexanitrostilbene (HNS)) were comprehensively analyzed with an ion trap mass spectrometer in negative ion mode using direct infusion electrospray ionization. MS/MS experiments were performed to generate fragment ions from the major parent ion of each explosive. Explosives in salt forms such as AP or AN provided cluster parent ions with their own anions. Explosives with an aromatic ring were observed as either $[M-H]^-$ for TNT and DNT or $[M]^{{\cdot}-}$ for HNS, while explosives without an aromatic ring such as RDX, HMX, and PETN were detected as an adduct ion with a formate anion, i.e., $[M+HCOO]^-$. These findings provide a guideline for the rapid and accurate detection of explosives once portable MS instruments become more readily available.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.05a
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• pp.30-33
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• 1992

This thesis was investigated on ion-induced characteristics in a-$Se_{75}Ge_{25}$ positive and negative resists for focused-ion-beam microlithogaphy. The exposed a-$Se_{75}Ge_{25}$ inorganic thin film shows an increase in optical absorption after exposure to~$10_{16}$ dose of Ga+. The observed shift in the absorption edge toward longer wavelengths is consistent with that in films exposed to band-gap photons(~$10^{21}$photons/cm2). This result may be related with microstructural rearrangements with in the short range of SeGe network. Due to changes in the short range order, the chemical bonding may be affected, which results in increased chemical dissolution in ion-induced film. Also, this resist exhibits good thermal stability because of its high Tg(~$220^{\circ}C$). When focused ion beams are used for direct exposure of resist over a substrate, unwanted implantation of the substrate may be an issue. A possible way to avoid this is to match the thickness of the resist to the range of ions in the resist. Thin aspect is currently under investigation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.6
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• pp.100-107
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• 2021

As a significant technology in the smartization era promoted by the Fourth Industrial Revolution, the secondary battery industry has recently attracted significant attention. The demand for lithium-ion batteries (LIBs), which exhibit excellent performance, is considerably increasing in different industrial fields. During the manufacturing process of LIBs, it is necessary to join the cathode and anode sheets with thicknesses of several tens of micrometers to lead taps of the cathode and anode with thicknesses of several hundreds of micrometers. Ultrasonic welding exhibits excellent bonding when bonded with very thin plates, such as negative and positive electrodes of LIBs, and dissimilar and highly conductive materials. In addition, ultrasonic welding has a small heat-affected zone. In LIBs, Cu is mainly used as the negative electrode sheet, whereas Cu or Ni is used as the negative electrode tab. In this study, one or two electrode sheets (t0.025 mm Cu) were welded to one lead tab (t0.1 mm Cu). The welding energy and pressure were used as welding parameters to determine the welding strength of the interface between two or three welded materials. Finally, the effects of these welding parameters on the welding strength were investigated.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.05a
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• pp.139-144
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• 2006

일반적인 PDP 에 적용된 ADS 방식에서 Reset 파형은 ON/OFF Cell 을 초기화 시켜주고 Wall charge를 쌓아줌으로써 낮은 Address 전압으로도 구동을 가능하게 해준다. 기존의 Reset 파형은 Positive ramp pulse를 이용하여 구현하고 있으나 본 논문은 Negative ramp pulse가 적용된 새로운 Reset 파형을 제안하고자 한다. 2-Dimensional fluid simulation code를 이용하여 Ramp부분에 초점을 맞춰 Reset파형을 분석했으며 제안된 Negative ramp reset 파형은 기존의 Positive ramp reset 파형보다 70V가 낮은 전압에서 방전이 발생되는 것을 확인했다. Negative ramp pulse를 적용됐을 경우, Positive ion들이 모두 Negative ramp pulse가 인가된 Scan전극으로 모이는 현상 때문에 기존 Reset파형에 의한 방전일 때보다 낮은 전압에서의 초기방전을 발생시키므로 Reset에 소요되는 시간과 전압을 감소시킬 수 있다.

• Journal of Industrial Technology
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• v.14
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• pp.63-75
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• 1994

The objective of this research is to analyze the phenomena of negative ion behavior in silane plasma chemical vapor deposition. Based on the plasma chemistry, the model equations for the formation and transport of negative ions were proposed and solved. The evolutions of gaseous species along the reactor were presented for several conditions of process variables such as reactor pressure, total gas flow rate, and electric field. Based on the model results, it is found that : (1) The concentration profiles of positive ions show the sharp peaks at the center of plasma reactor. (2) Most of negative ions are located in bulk plasma region, because the negative ions are excluded from the sheath region by electrostatic repulsion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.414-414
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• 2007

In this study, Liquid Crystal (LC) alignment and tilt angle generation in Nematic Liquid Crystal (NLC) with negative dielectric anisotropy on the homeotropic PI surface with new ion beam exposure are reported. Also. high density of ion beam energy (DuoPIGatron type Ar ion gun) is used in this study. The tilt angle of NLC on the homeotropic Polyimide (PI) surface for all incident angles is measured about 38 degree and this has a stabilization trend. And the good LC alignment of NLC on the PI surface with ion beam exposure of $45^{\circ}$ incident angle was observed. Also the tilt angle of NLC on the homeotropic PI surface with ion beam exposure of $45^{\circ}$ had a tendency to decrease as ion beam energy density increase. The tilt angle could be controlled from verticality to horizontality. Also, the LC aligning capabilities of NLC on the homeotropic PI surface according to ion beam energy has the goodness in case of more than 1500 eV. Finally. the superior LC alignment thermal stability on the homeotropic PI surface with ion beam exposure can be achieved. For OCB(Optically Compensated Bend) mode driving, we can need pretilt angles control for fast response time. In this study, We success pretilt angles control. Consequently, this result can be applied for OCB mode.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.310-311
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• 2011

Dual-frequency (DF) capacitively coupled plasmas (CCP) are used to separately control the mean ion energy and flux at the electrodes [1]. This separate control in capacitively coupled radio frequency discharges is one of the most important issues for various applications of plasma processing. For instance, in the Plasma Enhanced Chemical Vapor Deposition processes such as used for solar cell manufacturing, this separate control is most relevant. It principally allows to increase the ion flux for high deposition rates, while the mean ion energy is kept constant at low values to prevent highly energetic ion bombardment of the substrate to avoid unwanted damage of the surface structure. DF CCP can be analyzed in a fashion similar to single-frequency (SF) driven with effective parameters [2]. It means that DF CCP can be converted into SF CCP with effective parameters such as effective frequency and effective current density. In this study, comparison of DF CCP and its converted effective SF CCP is carried out through particle-in-cell/Monte Carlo (PIC-MCC) simulations. The PIC-MCC simulation shows that DF CCP and its converted effective SF CCP have almost the same plasma characteristics. In DF CCP, the negative resistance arises from the competition of the effective current and the effective frequency [2]. As the high-frequency current increases, the square of the effective frequency increases more than the effective current does. As a result, the effective voltage decreases with the effective current and it leads to an increase of the ion flux and a decrease of the mean ion energy. Because of that, the negative resistance regime can be called the preferable regime for solar cell manufacturing. In this preferable regime, comparison of DF (13.56+100 or 200 MHz) CCP and SF (60 MHz) CCP with the same effective current density is carried out. At the lower effective current density (or at the lower plasma density), the mean ion energy of SF CCP is lower than that of DF CCP. At the higher effective current density (or at the higher plasma density), however, the mean ion energy is lower than that of SF CCP. In this case, using DF CCP is better than SF CCP for solar cell manufacturing processes.

• Nuclear Engineering and Technology
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• v.5 no.2
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• pp.132-136
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• 1973

Uniformly irradiated parallel-plate ionization chamber filled with a gas free of negative ion-forming contaminants was studied. Computer solutions for the electric field and the positive and negative charge densities at various degrees of saturation were obtained and discussed.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.3
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• pp.160-171
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• 1993

Surface charge characteristics of Ultisol(Luisiana soil from Philippines), Alfisol(Maahas soil from Philippines), and Inceptisol(Yongii soil from Korea) were studied by way of potentiometric titration, backtitration technique, and ion adsorption method(or CEC - AEC method). The PZNC(point of zero net charge) values determined by ion adsorption method were much lower than the natural pHs in all soils, indicating that all soil samples bore net negative surface charge. The PZSE (point of zero salt effect) values determined by potentiometric titration and backtitration technique were identical in Luisiana and Yongii soils but not in Maaghas soil. All soils showed higher PZSE values than PZNC values probably due to the influence of permanent negative charge. The permanent charge calculated by the theory of Uehara and Gillman (1980) occupied quite low portion of the CEC measured at pH 7 in all soils. Backtitration technique corrected errors of potentiometric titration at extreme pH. However, it still overestimate the surface charge compared with ion adsorption method. Therefore, the ion adsorption method was recommanded for the surface charge measurement of the usual soils which have high negative charge components.