• Journal of the Korean Chemical Society
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• v.10 no.4
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• pp.166-174
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• 1966

The multistep mechanism of photosensitized curing reaction cinnamoylated photosensitive polymer is proposed from the energy level diagram of cinnamic acid and sensitizer, and from the fact that excess of sensitizer brings the sensitivity to a limiting value etc. Various factors which have effects on the ability of sensitizer are also discussed. The mechanism involves following steps: activation to the first excited singlet states of cinnamoyl group(C) and sensitizer(S) by their absorption of photon, their intersystem crossing to the lowest triplet state, bimolecular internal quenching by formation of excimer of sensitizer, triplet excitation energy transfer and intermolecular addition between cinnamoyl group in ground state and that in triplet state. The rate equation derived from this mechanism is $-\frac{d[C]}{dt} = \frac{K_1[C]}{K_2 + [C]}[\frac{I^c_{abs}}{K_3 + [S]} + \frac{K_4[C]}{(K_5 + [C])(K_6 + [S])}(I^s_{abs} + \frac{K_7I^c_{abs}[S]}{K_8 + [S]})]$ where $I^c_{abs}\;and\;I^s_{abs}$: the rates of absorption of photon by cinnamoyl group and sensitizer $K_n$: Constants. It is proved with the cinnamate of poly(glyceryl phthalate)(PGC) in the absence of sensitizer using the infrared analytical method and successfully applied for the experimental data reported on the effects of the degree of cinnamoyl esterification and the concentration of sensitizer upon the sensitivity.

• Journal of the Korean Chemical Society
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• v.37 no.3
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• pp.271-278
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• 1993

The hyperfine splitting constants of phenanthrenequinone anion radical have been determined for the solution of triethylamine with 2-propanol, 2-pentanol or benzene by cwESR and time-resolved ESR methods. The radical anion was produced by photolysis using a pulsed excimer laser. The resulting hyperfine splitting constant A$_{H1}$ and A$_{H2}$ are 1.662, 0.378 in 2-propanol, 1.602, 0.361 in 2-pentanol and 1.518 in benzene respectively. The hyperfine coupling constants decrease with the decreasing of polarity of the mixed solvent. The tendency of the variation depends on the polarity of the solvents, thus, making it in impossible to observe the magnetic equivalent proton in a mixed solvent of nonpolar benzene. Particularly, time-resolved ESR spectrum of triethylamine radical (TEA${\cdot}$) has been observed in 0.15∼0.30 ${\mu}s$ from the solvent of 3 : 1 with 2-pentanol and triethylamine. Thus from the results of solvent effect, we can suggest that the identification of the unstable short-lived spin polarized phenanthrenequinone anion radical(*PQ${\cdot}^-$) proceed through photochemistry.

• Korean Journal of Optics and Photonics
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• v.4 no.1
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• pp.15-21
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• 1993

This paper describes the design and development of a KrF excimer laser stepper and discusses the detailed system parameters and characterization data obtained from the performance test. We have developed a deep UV step-and-repeat system, operating at 248 nm, by retrofitting a commercial modules such as KrF excimer laser, precision wafer stage and fused silica illumination and 5X projection optics of numerical aperture 0.42. What we have developed, to the basic structure, are wafer alignment optics, reticle alignment system, autofocusing/leveling mechanisms and environment chamber. Finally, all these subsystem were integrated under the control of microprocessor-based controllers and computer. The wafer alignment system comprises the OFF-AXIS and the TTL alignment. The OFF-AXIS alignment system was realized with two kinds of optics. One is the magnification system with the image processing technique and the other is He-Ne laser diffraction type system using the alignment grating on the wafer. 'The TTL alignment system employs a dual beam inteferometric method, which takes advantages of higher diffraction efficiency compared with other TTL type alignment systems. As the results, alignment accuracy for OFF-AXIS and TTL alignment system were obtained within 0.1 $\mu\textrm{m}$/ 3 $\sigma$ for the various substrate on the wafers. The wafer focusing and leveling system is modified version of the conventional systems using position sensitive detectors (PSD). This type of detection method showed focusing and leveling accuracies of about $\pm$ 0.1 $\mu\textrm{m}$ and $\pm$ 0.5 arcsec, respectively. From the CD measurement, we obtained 0.4 $\mu\textrm{m}$ resolution features over the full field with routine use, and 0.3 $\mu\textrm{m}$ resolution was attainable under more strict conditions.

• Journal of the Korean Magnetics Society
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• v.5 no.2
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• pp.128-133
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• 1995

Yttrium Iron Garnet($Y_{3}Fe_{5)O_{12}$) films have been succsssfully grown on(111)GGG wafer by KrF excimer laser ablation of stoichiometric garnet target at the oxygen partial pressure, $P(O_{2}$, ranging 20 to 500 mTorr. During the deposition of the films the substrate temperature was maintained at $700^{\circ}C$ and the laser beam energy density at $7.75\;J/cm_{2}$. Microstructure, composition and magnetic properties of the films obtained were investigated as a function of oxygen pressure and thickness of the films. Epitaxial films with a dense and a smooth surface were reproducible at a low oxygen pressure. The films of $2.75\;{\mu}$ min thickness deposited at 20 mTorr of $P(O_{2})$ showed $4{\pi}M_{s}$ of 1500 Gauss and $H_{c}$ of 3 Oe after annealing at $800\;^{\circ}C$ for 20 minutes. As-deposited films of $0.8\;\mu\textrm{m}$ in thickness exhibited the $4{\pi}M_{s}$ of 1730 Gauss and $H_{c}$ of 7 Oe. The magnetic properties of the films obtained were almost identical to those of a single crystal YIG.

• Applied Chemistry for Engineering
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• v.17 no.2
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• pp.158-162
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• 2006

Poly[4-hydroxystyrene-co-2-(4-methoxybutyl)-2-adamantyl methacrylate] was synthesized and evaluated as a matrix resin for extreme UV (EUV) chemically amplified resist. The resist system formulated with this polymer resolved 120 nm line and space (pitch 240 nm) positive patterns using a KrF excimer laser scanner (0.60 NA). The well defined 50 nm line positive patterns (pitch 180 nm) were obtained using an EUV lithography tool. The dry etching resistance of this resist for a $CF_{4}$-based plasma was 1.1 times better than that of poly(4-hydroxystyrene).

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.27 no.3
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• pp.205-212
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• 2014

Purpose: This study aims to prove effects of an oriental medical complex therapy on vitiligo patients who have experienced the Eximer laser therapy. Method: The study conducted its investigation targeting these four patients who have not been observed with any satisfactory reaction to the Eximer laser therapy. The study analyzed the findings through the comparison on the pictures before and after the therapy. Result: After comparing the pictures, the study confirmed positive changes in the conditions of the patients. The oriental medical complex therapy turned out to be effective enough to treat the patients who have gone through the Eximer laser therapy before. Conclusion: Such result leads the study to a conclusion that the oriental medical complex therapy can be an effective way to treat these patients who do not have a satisfactory reaction to the Eximer laser therapy. In addition, the author of the study suggests that more clinical trials should be conducted.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.348-353
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• 2001

Experimental schemes that enable characterization of phase-change phenomena in the micro scale regime is essential for understanding the phase-change kinetics. Particularly, monitoring rapid vaporization on a submicron length scale is an important yet challenging task in a variety of laser-processing applications, including steam laser cleaning and liquid-assisted material ablation. This paper introduces a novel technique based on Michelson interferometry for probing the liquid-vaporization process on a solid surface heated by a KrF excimer laser pulse (${\lambda}=248nm,\;FWHM=24\;ns$) in water. The effective thickness of a microbubble layer has been measured with nanosecond time resolution. The maximum bubble size and growth rate are estimated to be of the order of $0.1{\mu}m\;and\;1\;m/s$, respectively. The results show that the acoustic enhancement in the laser induced vaporization process is caused by bubble expansion in the initial growth stage, not by bubble collapse. This work demonstrates that the interference method is effective for detecting bubble nucleation and microscale vaporization kinetics.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.957-961
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• 2004

In order to realize high performance thin film transistor (TFT) on plastic substrate, Si film was deposited on plastic substrate at 170$^{\circ}C$ by using inductivity coupled plasma chemical vapor deposition (ICPCVD). Hydrogen concentration in as-deposited Si film was 3.8% which is much lower than that in film prepared by using conventional plasma enhanced chemical vapor deposition (PECVD). Si film was deposited as micro crystalline phase rather than amorphous phase even at 170$^{\circ}C$ because of high density plasma. By step-by-step Excimer laser annealing, dehydrogenation and recrystallization of Si film were carried out simultaneously. With step-by-step annealing and optimization of underlayer structure, it has succeeded to achieve large grain size of 300nm by using ICPCVD. Base on these results, poly-Si TFT was fabricated on plastic substrate successfully, and it is sufficient to drive pixels of OLEDs, as well as LCDs.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.860-865
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• 2004

Field emission display(FED) using carbon nanotubes (CNT) as field emitters is expected to large-area panels with high luminance and low power consumption. In order to perform the uniform luminance with low driving voltage, we introduced a new electrode to apply higher electric potential over the CNT cathode in 2003.[1] In the study, we described the luminance uniformity of the panel and the improvement of emission uniformity by increasing the emission-site density. The luminance uniformity of the several ideal dots which were selected over the display area in the panel was 2.8%. [2] The CNT cathode was irradiated by excimer-laser, which was effective to improve emission uniformity and lower driving voltage. A prototype of CNT-FED character display was performed for middle size message displays. The prototype panel had 48 x 480-dots and the resolution was 1-mm. The panel realized high luminance at low power consumption. It will be important characteristics for legible and ubiquitous displays. [3]

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.95-97
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• 2004

We studied a low temperature ion doping process for poly-Si Thin Film Transistor (TFT) on plastic substrates. The ion doping process was performed using an ion shower system, and subsequently, excimer laser annealing (ELA) was done for the activation. We have studied the crystallinity of Si surface at each step using UV-reflectance spectroscopy and the sheet resistance using 4-point probe. We found that the temperature has increased during ion shower doping for a-Si film and the activation has not been fulfilled stably because of the thermal damage against the plastic substrate. By trying newly a pulsed ion shower doping, the ion was efficiently incorporated into the a-Si film on plastic substrate. The sheet resistance decreased with the increase of the pulsed doping time, which was corresponded to the incorporated dose. Also we confirmed a relationship between the crystallinity and the sheet resistance. A sheet resistance of 300 ${\Omega}$/sq for the Si film of 50nm thickness was obtained with a good reproducibility. The ion shower technique is a promising doping technique for ultra low temperature poly-Si TFTs on plastic substrates as well as those on glass substrates.