• Journal of the Korean Society for Precision Engineering
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• v.20 no.12
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• pp.42-47
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• 2003

The laser direct writing method has some advantages of being maskless, allowing rapid and inexpensive prototyping in comparison to conventional mask-based photolithography. In general, there are two kinds of laser direct writing methods such as the laser ablation method and the laser polymerization method. The laser polymerization method was studied fur manufacturing waveguide in this paper. It is important to reduce line width for image mode waveguides, so some investigations will be carried out in various conditions of process parameters such as laser power, writing speed, focusing height and optical properties of polymer. Experimentally, the optical waveguide was manufactured trapezoid shape. Through SEM the waveguide was 20 ${\mu}{\textrm}{m}$ width and 7.4 ${\mu}{\textrm}{m}$ height.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.139-142
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• 1998

PLZT thin films were fabricated with different Zr/Ti ratios by pulsed laser deposition. PLZT films deposited on Pt/Ti/SiO$_2$/Si substrate. This PLZT thin films of 5000${\AA}$. thickness were crystallized at 600$^{\circ}C$, 200 mTorr O$_2$ press. 2/55/45 PLZT thin film showed a maximum dielectric constant value of $\varepsilon$$\_$r/=1500, and dielectric loss was 0.O$_3$. At 2/70/30 PLZT thin film, Coercive field and remnant polarization was respectively 19[kV/cm], 8[${\mu}$C/$\textrm{cm}^2$].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.122-125
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• 1999

(Ba$_{0.6}$Sr$_{0.4}$)TiO$_3$(BST) thin films were fabricated with different deposition temperature and oxygen pressure by Pulsed Laser Deposition(PLD). Energy Dispersive Spectroscopy(EDS) proved that BST thin films prepared by PLD have almost the same stoichiometric composition as the BST target materials. This BST thin films were fully crystallized at $650^{\circ}C$, 300mTorr oxygen pressure and showed a maximum dielectric constant value of $\varepsilon$$_{t}$=684 and dielectric loss was 0.01 at 75$0^{\circ}C$, 300mTorr oxygen pressure.ssure.

• Proceedings of the KIEE Conference
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• 1998.11b
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• pp.698-701
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• 1998

PLT(28) ($Pb_{0.72}La_{0.28}Ti_{0.93}O_3$) dielectric thin films have been deposited on Pt/Ti/$SiO_2$/Si substrates in situ by a laser ablation. We have systematically changed the laser fluence from $0.5\;J/cm^2$ to $3\;J/cm^2$, and deposition temperature from $450^{\circ}C$ to $700^{\circ}C$. The surface morphology was changed from planar grain structure to columnar structure as the nucleation energy was increased. The PLT thin film with columnar structure showed good dielectric properties. It is shown that the deposition temperature strongly affect the film nucleation compared with the laser fluence.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.165-168
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• 2000

로켓엔진에서 노즐은 추력을 발생하고, 단위 면적당 열 전달이 최대가 되는 곳으로 구조적으로 가장 취약한 부분이다. 이런 가혹한 조건에서 사용되어질 수 있는 4D 탄소/탄소 복합재를 제조하였으며. 초밀도화시, 탄화압력은 100bar 와 900bar 에서 각각 시행되었다. 만들어진 시편의 밀도는 1.5~l.9g/$cm^3$ 이었다. 실제 로켓을 모사할 수 있는 지상연소시험을 통해 밀도에 따른 삭마율을 계산한 결과, 밀도가 높을수록 삭마율은 감소하였다. 또한 3-point bending test를 통해 굽힘강도(flexural strength)를 측정하였으며, 굽힘강도를 개선시켜주었다.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1256-1258
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• 1993

Optical data storage offer high density storage and archival storage capability. In this study, we selected the ablation mechanism-one of an irreversible recording system-using the antireflection trilayer(ART) structure. Optical recording medium is a $(Te_{86}Se_{14})_{50}Bi_{50}$ thin films. Actually, ART structure is fabricated and compared to monolayer structure. ART structure leads to the reduction of recording power as well as an increase in the effciency compared to the monolayer structure.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.378-381
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• 1998

PLT(28) ($Pb_{0.72}La_{0.28}Ti_{0.93}O_3$) dielectric thin films have been deposited on Pt/Ti/$SiO_2$/Si substrates in situ by a laser ablation. We have systematically changed the laser fluence from $0.5\;J/cm^2$ to $3\;J/cm^2$, and deposition temperature from $450^{\circ}C$ to $700^{\circ}C$. The surface morphology was changed from planar grain structure to columnar structure as the nucleation energy was increased. The PLT thin film with columnar structure showed good dielectric properties. It is shown that the deposition temperature strongly affect the film nucleation compared with the laser fluence.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.720-725
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• 1995

Bi-substituted gadolinium iron garnet films were deposited on GGG(111) and NGG (111) substrates by irradiating KrF excimer laser onto targets having compositions of $Bi_{x}Gd_{3-x}Fe_{5}O_{12}$ ($2.0{\leq}x{\leq}3.0$) under substrate temperature of $580~620^{\circ}C$. Analysis on structure, composition and angle of Faraday rotation, ${\theta}_{F}$, were carried out. The composition, the structure and the magneto-optical properties of the obtained films were found to be strongly dependent both on the compositions of the targets and on the pressure of oxygen. Before annealing in air, all films showed ${\theta}_{F}{\geq}0$ at ${\lambda}=6328{\AA}$, while several films showed ${\theta}_{F}{\leq}0$ after the annealing. The highest value of Bi-substitution up to x = 1.76 with uniform composition was obtained.

• Korean Journal of Materials Research
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• v.28 no.3
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• pp.135-141
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• 2018

Stainless steel is being used in various industries such as automobile and aerospace for its cheap manufacturing cost and excellent mechanical properties. However, stainless steel failed to stably protect a specimen with a $Cr_2O_3$ protective layer at temperatures above $1000^{\circ}C$. Thus, improving the high temperature flame resistance of the specimen through additional surface coating was needed. In this study, multilayer coatings of YSZ and $Al_2O_3$ were performed on SUS 304 specimens using pack cementation coatings and thermal plasma spray. The multilayer coated specimen showed enhanced thermal properties due to the coated layers. The microstructures and phase stability are discussed together with flame conditions at $1350^{\circ}C$.

• Progress in Superconductivity
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• v.2 no.1
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• pp.51-55
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• 2000

A $Y_1Ba_2Cu_3O_{7-\delta}$ square spiral microstrip antenna (YBCO antenna) was epitaxially grown on a $LaAlO_3$ substrate by laser ablation. Also fabricated was a gold square spiral microstrip antenna (gold antenna) having the same structure as that of the YBCO antenna in order to compare the properties of both antennas. Both the YBCO antenna and the gold antenna were operated in Ku (12-18 GHz) band, and their properties such as the return loss, SWR, power gain, and radiation patterns were investigated at 77 K. The return loss below -10 dB was obtained in two frequency ranges, i.e., 14.05-14.90 GHz, and 16-18 GHz for the YBCO antenna at 77 K (YBCO superconducting antenna), and in the frequency range of 15.05-17.60 GHz for the gold antenna at 77 K. The SWR bandwidths are 0.85 GHz and 2 GHz for the YBCO superconducting antenna, and 2.55 GHz for the gold antenna at 77 K. The gain improvement of the superconducting YBCO antenna over the gold antenna at 77 K was about 10 dB in the frequency range of 16 GHz to 18 GHz. The radiation patterns show the YBCO superconducting antenna has the omni-directional property of a spiral antenna.