• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1334-1336
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• 2001

In this study, laser ablation atomic fluorescence (LAAF) spectroscopy has been applied for a nanometer-scale surface analysis of Na-doped polymethyl methacrylate (PMMA). LAAF spectroscopy is a new sensitive element detection technique which involves atomizing of a sample by the laser ablation and detection of ablated plume by laser-induced fluorescence (LIF) spectroscopy. Using this technique in the detection of Na atoms with Na-doped PMMA, a detection limit is obtained as 36 fg for single laser shot. Further, the depth distribution in the sample is measured with a very high spatial resolution using a two-layer PMMA sample by observing the shot-by-shot LIF intensity from the Na atoms.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.12a
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• pp.96-100
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• 2006

A pulsed laser ablation deposition (PLAD) technique is an excellent method for the fabrication of amorphous carbon (a-C) films. This paper was focused on the understanding and analysis of the motion of carbon atom (C) and carbon ion ($C^+$) particles in laser ablation assisted by Ar plasmas. The simulation has carried out under the pressure P=10~100 mTorr of Ar plasmas. Two-dimensional hybrid model consisting of fluid and Monte-Carlo models was developed and three kinds of the ablated particles which are C, $C^+$ and electron were considered in the calculation of particle method. The motions of energetic $C^+$ and C deposited upon the substrate were investigated and compared.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.736-742
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• 2000

Mass removed from crystalline silicon samples during high power single-pulse laser ablation was studied by measuring the resulting crater morphology with a white light interferometric microscope. The volume and depth of the craters show a strong nonlinear change as the laser irradiance increases across a threshold value, that is, approximately $2.2{\times}10^{10}\;W/cm^2$. Time-resolved shadowgraph images of the ablation plume show the ejection of large particulates from the sample for laser irradiance above the threshold, with a time delay of about 300-400 nsec. The thickness of superheated liquid layer near the critical temperature was numerically estimated, considering the transformation of liquid metal into liquid dielectric near the critical state (i.e., induced transparency). The estimated thickness of the superheated layer at a delay time of 200 nsec agreed with the measured crater depths, suggesting that induced transparency promotes the formation of a deep superheated liquid layer which leads to an explosive boiling responsible for the sudden increase of crater volume and depth.

• Bulletin of the Korean Chemical Society
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• v.35 no.7
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• pp.2093-2096
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• 2014

2H-azirine, a less known acetonitrile isomer, is observed in matrix IR spectra from the precursor exposed to radiation from laser ablation of transition-metals. Its vibrational characteristics confirm the previous results, and those for the deuterated and $^{13}C$ substituted isotopomers are also newly reported. The weak absorptions are traced to the low production yield due to its high energy and low extinction constants. IRC computations reveal smooth inter-conversion between 2H-azirine and $CH_2NCH$, providing a rationale for the observed variation of their relative contents during photolysis.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.798-802
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• 2010

From time-resolved optical emission spectra, we have investigated the effects of a transverse magnetic field on the expansion of a plasma plume produced by laser ablation of a ZnO:$P_2O_5$ ceramic target in oxygen active atmosphere. The emission spectra of $Zn^{+*}$, $P^{+*}$, and $Zn^*$ neutrals in the presence of magnetic field turn out to be considerably different from those without magnetic field. The characteristics of the deposited films grown on amorphous fused silica substrates by pulsed laser deposition (PLD) are examined by analyzing their photoluminescence (PL), X-ray diffraction (XRD), and UV-visible spectra.

• Journal of Photoscience
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• v.6 no.3
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• pp.141-144
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• 1999

A Spectroscopic study on a pulme produced by a reactive laser pulse irradiates the graphite target in a nitrogen atmosphere, two emission bands of C2(d3IIg longrightarrowa3 IIu, Swan band) and CN(B2$\Sigma$+ longrightarrowX$^2$$\Sigma$+, Violet band ) were observed. By simulation of the optical emissionspectra, spectroscopic temperature of $C_2$ and CN molecules were obtained. The depended of vibrational and rotational temperatures on the laser fluence and distance from the target as well as the pressure dependence of the emission intensities of $C_2$ and CN was examined to elucidate the expansion dynamics of the plume and formation mechanisms of $C_2$and CN molecules.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.05a
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• pp.15-19
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• 2006

A pulsed laser ablation deposition (PLAD) technique is an excellent method for the fabrication of amorphous carbon (a-C) films, because it can generate highly energetic carbon clusters on a substrate. This paper was focused on the understanding and analysis of the motion of C particles in laser ablation assisted by Ar plasmas. The simulation has carried out under the pressure P=50 mTorr of Ar plasmas. Two-dimensional hybrid model consisting of fluid and Monte-Carlo models was developed and three kinds of the ablated particles which are carbon atom (C), ion ($C^+$) and electron were considered in the calculation of particle method. The motions of energetic $C^+$ and C deposited upon the substrate were investigated and compared. The interactions between the ablated particles and Ar gas plasmas were discussed.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1408-1409
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• 2007

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 modeling, we adopt capacitively coupled plasma with ring electrode inserted in the space between the substrate and the target, graphite. This system may take an advantage of ${\mu}m$-sized droplets from the sheath electric field near the substrate. 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.

• Bulletin of the Korean Chemical Society
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• v.34 no.5
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• pp.1361-1365
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• 2013

The smallest ketenimine and hydrogen cyanide N-methylide ($CH_2CNH$ and $CH_2NCH$) are provided from the argon/acetonitrile matrix samples exposed to radiation from laser ablation of transition-metals. New infrared bands are observed in addition to better determination of the vibrational characteristics for the previously reported bands, and the $^{13}C$ substituted isotopomers ($^{13}{CH_2}^{13}CNH$ and $^{13}CH_2N^{13}CH$) are also generated. Density functional frequency calculations and the D and $^{13}C$ isotopic shifts substantiate the vibrational assignments. $CH_2CNH$ is probably produced through single-step conversion of $CH_3CN$, whereas $CH_2NCH$ through two-step conversion via 2H-azirine. Inter-conversions between these two products evidently do not occur during photolysis and annealing.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.365-368
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• 2009

A new concept of a small thruster for altitude control of a micro/nano class satellite is developed, which utilizes the pulsed laser energy. As the laser-based thruster does not require burning of any fuel, it gives promise of small satellite design criteria, namely light weight and cost effectiveness. In this paper, we develop gel-type material for generating strong plasma plume for enhancing thrust for propulsion. Moreover, we quantify the level of thrust via the momentum coupling coefficient measured by the pendulum system. We discover that the driving force is significantly improved via the gel-typed propellant for laser ablation.