• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 춘계학술대회 논문집
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• pp.58-61
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• 1995

레이저 유기에 대한 GaAs 의 건석에칭에 있어서 기존의 $CCl_4$와CCl$_2$F$_2$ 가스를 에칭하스로 사용하는 대신에 본 연구팀이 새로 개발한 CFCs 대체가스를 사용하여 기존의 가스와의 에칭률과 그 가공된 형태를 비교하였다. 실험은 power 밀도 12.7 MW/$\textrm{cm}^2$에서 27 MW/$\textrm{cm}^2$까지로 가변시키면서 하고 에칭가스의 압력은 260 Torr에서760 Torr 까지 변화를 주면서 하였다. 빔의 주사속도는 8.3$\mu\textrm{m}$/sec에서 80$\mu\textrm{m}$/sec 까지 가변을 시켰다. 그 결과 CHCiF$_2$가스에서의 에칭율(etch rate)은 최대 136$\mu\textrm{m}$/sec이고 aspect ratio 는 2.6 이 됨을 알 수 있었다. 애칭된 형태를 측정하기 위해서 SEM(Scanning Electron Microscopy)을 사용하였으며, 시료 표면의 물질 분석을 위해서 AES(Auger Electron Spectroscopy)를 사용하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제48권8호
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• pp.587-590
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• 1999

In this study, it is the purpose to develope a cheap and compact $CO_2$ laser and to apply 60 Hz AC discharges as a new exciting source. An axial and water cooledtype was adopted as the laser mode. The laser performance characteristics as various parameters, such as gas pressure and discharge current, have been investigated. And the laser output and the efficiency of DC and 60 Hz AC discharge-exciting type have been measured and compared for the different input powers at the static operational pressure. As a result, the case of 60 Hz AC discharge-exciting type, the laser oscillation began at the condition of operational pressure 6 Torr and discharge current 5 mA. A maximum laser output of about 32 W was obtained at an operational pressure of 18 Toorr and a discharge current of 30 mA. In addition, the laser output was saturated from an operational pressure of about 14 Torr and a discharge current of about 20 mA. In this $CO_2$ laser, the laser output of 60 Hz AC discharge-exciting type was slightly higher than that of DC discharge-exciting type. And the laser efficiency was about 10 to 13% for the various operational pressures and the discharge currents.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1307-1310
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• 1995

During measurement of atomic hydrogen in a silane plasma using two-photon excited laser induced fluoresecence, laser-induced dissociation of the gas was observed. This was investigated untill conditions for the input laser fluence were determined where the effect was negligible. A measurement of the atomic hydrogen distribution was then performed within the limits of these conditions. Absolute density determinations showed atomic hydrogen densities of around $3{\times}10^{17}m^{-3}$.

• 한국광학회:학술대회논문집
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• 한국광학회 1990년도 제5회 파동 및 레이저 학술발표회 5th Conference on Waves and lasers 논문집 - 한국광학회
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• pp.59-63
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• 1990

Two-stage TEA(transversely excited atmospheric pressure) CO2 laser amplifier system, Amp I and Amp II are consturcted and their amplification characteristics are investigated theoretically and experimentally. Multiple-wire corona preionization method is used for uniform discharge in laser oscillator and amplifiers. At optimumm gas ratio, CO2 : N2 : He = 1 : 1 : 3, output pulse energy of the oscillator is 0.4J and finally two-stage amplification gives 1.5J output energy which is larger than pumping threshold of para-H2 Raman laser. The rate equations of the amplifiers are solved numerically, and the results are compared with the experimental results. In conclusion, the small signal gain cocfficient of AMP I is 0.025/cm and that of AMP II is 0.02/cm.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 춘계학술대회 논문집 센서 박막재료연구회 및 광주 전남지부
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• pp.22-26
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• 2008

In this paper, we developed a hybrid simulation model of carbon laser ablation under the Ar plasmas consisted of fluid and particle methods. Three kinds of carbon particles, which are carbon atom, ion and electron emitted by laser ablation, are considered in the computation. In the present simulation, we adopt capacitively coupled plasma with asymmetrical electrodes. As a result, in Ar plasmas, carbon ion motions were suppressed by a strong electric field and were captured in Ar plasmas. Therefore, a low number density of carbon ions were deposited upon substrate. In addition, the plume motions in Ar gas atmosphere was also discussed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.127-130
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• 2001

Si thin films on p-type (100) Si substrate have been fabricated by pulsed laser deposition technique using a Nd:YAG laser. The pressure of the environmental gas during deposition was 1 Torr. After deposition, Si thin film has been annealed again at 400-840$^{\circ}C$ in nitrogen ambient. Strong blue photoluminescence (PL) have been observed at room temperature. We report the PL properties of Si thin films depending on the variation of the annealing temperature.

• E2M - 전기 전자와 첨단 소재
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• 제9권3호
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• pp.240-245
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• 1996

Non-ozone layer destructive Chlorofluorocarbon(CFC) altematives(CHCIF$_{2}$ and $C_{2}$H$_{2}$F$_{4}$) have been initially used for laser-induced thenrmochemical etching of GaAs. High etching rate up to 188.mu.m/sec and an aspect ratio of 2.7 have been achieved by a single scan of laser beam, respectively. The etching rate at constant ambient gas pressure was found to saturate for beam power. The chemical compositions of the reaction products deposited on the etched groove were measured by Auger electron microscopy(AES). Etched profile, depth and width were observed by scanning electron microscope(SEM).

• Journal of Welding and Joining
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• 제20권2호
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• pp.71-76
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• 2002

Currently knowledge of strain in welds has mainly been obtained from strain gage method; that is directly attaching the gage to the most of the material. The very flew non-contact methods are still in the early stage. One of the non-contact methods is by the use of the laser that has high-level of the accuracy for the measurement, and this laser also has excellent characteristics on which many studies for its applications are focused throughout the many fields. The paper is on the measurement of the strain caused by the characteristics and the temperature changes of the GTA welded zone employed with 3D ESPI system that is functionally modified through the laser ESPI system. This system may be applied the steel plate such as for the electronics, chemistry, flood instrument and electronic appliances.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.123-124
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• 2006

This study aimed at exploiting low heat input characteristic of laser welding to effectively control grain coarsening in the fusion zone(FZ) and heat affected zone(HAZ) of 1.5mm thick 18wt% Cr ferritic stainless steel weld. The study demonstrated that as compared with gas tungsten arc welding(GTAW), laser welding brought about significant grain refinement in the FZ and HAZ. However, the impact absorbed energy of GTA weld was superior than that of laser weld because the strengthening effect during welding and cooling stage was higher In laser weld than that in GTA weld. The coarser grains in each weld than base metal resulted in an inferior toughness.

• Journal of Welding and Joining
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• 제34권5호
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• pp.6-12
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• 2016

This study was performed bead welding of pure titanium by using fiber laser. Since titanium is very sensitive to oxidation and nitriding during welding, it is important to compose the shielding equipment compared with different material. Thus side and coaxial shield nozzle, rail and chamber type shielding equipment are widely used to protect effectively the weld during welding. Experiments were performed by changing nozzle angle and distance using side and coaxial shield nozzle. The bead colors of gold, brown, blue, purple and yellowish white were obtained by changing variables of shield nozzle, and then its weldability was investigated. As experiment result, sound and not brominated beads were formed when side nozzle angle and distance were respectively $45^{\circ}$ and 10 mm.