• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.121-124
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• 1997

Emergence of advanced materials has been realized by the great demands for sophisticated state devices in high technology industry. It is the ear of speedy evolution of science and technology, in particular, materials processing technology, which enables us to synthesize any materials with respect to its purity and its perfection of crystal structure and shape (form) that have, heretofore not been available. The availability of ultra pure, fine raw materials, single crystals and thick/thin film materials has been largely responsible for such startling progresses that have been made in the realization of unforeseen, functional devices for high technology industry. Of the functional devices such as passive as active devices, non-silicon devices are mostly passive. Piezoelectric, electro-optic, magneto-optic devices, etc. are some of the examples. In this paper, magneto-optic materials for Faraday device, which is little known, are reviewed including its processing toward practical applications.

• Journal of Powder Materials
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• v.16 no.6
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• pp.403-409
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• 2009

Plasma spray forming is recently explored as a near-net-shape fabrication route for ultra-high temperature metals and ceramics. In this study, monolithic tungsten has been produced using an atmospheric plasma spray forming and subsequent high temperature sintering. The spray-formed tungsten preform from different processing parameters has been evaluated in terms of metallurgical aspects, such as density, oxygen content and hardness. A well-defined lamellae structure was formed in the as-sprayed deposit by spreading of completely molten droplets, with incorporating small amounts of unmelted/partially-melted particles. Plasma sprayed tungsten deposit had 84-87% theoretical density and 0.2-0.3 wt.% oxygen content. Subsequent sintering at 2500$^{\circ}C$ promoted the formation of equiaxed grain structure and the production of dense preform up to 98% theoretical density.

• Journal of the Korean Ceramic Society
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• v.17 no.4
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• pp.203-207
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• 1980

The optical absorption of high index glasses of the system TiO2-BaO-B2O3 prepared from the raw materials for an optical waveguide glass has been measured in the near ultraviolet region. The amount of Ti3+ in the glass could be reduced to a level less than 5 ppm by melting a batch added with pure nitric acid, using a fused quartz crucible in an oxygen gas atmosphere. The ultra-pure glass of 10mm thick prepared in such a way did not show any appreciable color even for the one containing 30 mol% TiO2 and having refractive index nD of 1.84 and Abbe's number vD of 28.8. The wavelength of ultraviolet absorptin edge was longer for the glass of higher index and higher dispersdion. The melting of a TiO2 containing glass in a platinum crucible resulted in a coloration of the glass due to the dissolved plutinum from the crucible, which was more intense for the one containing larger amount of TiO2.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.06a
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• pp.40-44
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• 2006

Sandwich structures, which are composed of a thick core between two faces, are commonly used in many engineering applications because they combine high stiffness and strength with low weight. Accordingly, the usage of sandwich structure is very widely applied to the aircraft, the automobile and marine industry, etc., because of these advantages. In this paper, we have investigated the buckling protection of an inner structure plate and the useful corrugated configuration for contact, and the fabrication method of the inner structure plate for large area using the continuous molding process. Also, we have guaranteed the accuracy of the molding process through the micro corrugated mold fabrication and secured the accuracy and analyzed aspect properties of the inner structure plate fabricated for a large area using the partial mold process.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.5
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• pp.80-90
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• 1998

The EPS construction method-one kind of the load reducing methods-utilizes the EPS blocks, ultra-light materials whose unit weight is about 1/100 of soils and has been applied to many soft ground sites. It needed 3,000 days to get the 90% degree of the consolidation for the case of 12m high soil embankments on the 30m thick soft clayey foundations. The N value of SPT at this deposit was less than 5. The pack drain was installed to promote the radial consolidations. Although staged embankments were planned, designers failed to get a sufficient stability of the foundation ground. Therefore, the EPS fill method was selected to reduce the load and the construction period. EPS blocks(D-20 model) replaced the upper part of the soil embankments. These complex embankments reduced the ground settlement and the construction period. The possibility of lateral movements of the bridge abutments was checked and the design scheme was reviewed.

• Journal of the Optical Society of Korea
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• v.13 no.1
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• pp.158-165
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• 2009

We present cross-correlation frequency-resolved optical gating (XFROG) measurements of supercontinuum pulses generated by using a photonic crystal fiber (PCF), and ultraviolet (UV) pulses generated by frequency doubling of infrared ultra-short pulses. Since supercontinuum pulses have broad spectra, XFROG measurement typically requires using an extremely thin nonlinear crystal which has a thickness of sub-ten microns. Instead of using such a thin crystal, we employed a relatively thick crystal which was mounted on a galvanometer in order to achieve a phase-matching over the whole spectral bandwidth of the supercontinuum pulses by a crystal-dithering technique. Experimental results of the retrieved phase and intensity were in fair agreement with the independently measured data.

• Electrical & Electronic Materials
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• v.9 no.1
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• pp.59-66
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• 1996

Polyimides containing cyclobutane ring in main chain is known to be thermally stable and able to be developed in organic solvents after photolysis with 254 nm UV light. This type of polyimides can be used as promising positive photoresist in VLSI fabrication process. In the current VLSI process, photoresist films are formed by spin coating. The film thickness is more than several hundred nano meters. It seems that there is room for improvement of film coating process by introducing Langmuir Blodgett technique. Thereby ultra thin film photoresist can be formed, and higher density of integration in VLSI be achieved. In the present work, depositing procedure of LB films of this polyimide was investigated. LB film thickness was measured by ellipsometry to evaluate deposited film status. Chemical imidization procedure was studied to avoid several problems in thermal imidization. The pattern of submicron dimension has successfully formed on LB film of 8nm thick, which found showing good contrast.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.569-572
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• 2000

This paper presents the optimized fabrication and thermal characteristics of micro-heaters for thermal MEMS applications using a SDB SOI substrate. The micro-heater is based on a thermal measurement principle and contains for thermal isolation regions a 10$\mu\textrm{m}$ thick silicon membrane with oxide-filled trenches in the SOI membrane rim. The micro-heater was fabricated with Pt-RTD(Resistance Thermometer Device)on the same substrate by using MgO as medium layer. The thermal characteristics of the micro-heater with the SOI membrane is 280$^{\circ}C$ at input Power 0.9 W; for the SOI membrane with 10 trenches, it is 580$^{\circ}C$ due to reduction of the external thermal loss. Therefore, the micro-heater with trenches in SOI membrane rim provides a powerful and versatile alternative technology for improving the performance of micro thermal sensors and actuators.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.29-30
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• 2005

Experimental results are presented for the degradation of 3 nm-thick gate oxide ($SiO_2$) under both Negative-bias Temperature Instability(NBTI) and Hot-carrier-induced(HCI) stresses using P and NMOSFETs that are annealed with hydrogen or deuterium gas at high-pressure (1~5 atm.). Statistical parameter variations depend on the stress conditions. We suggest that deuterium bonds in $SiO_2$ film is effective in suppressing the generation of traps related to the energetic hot electrons.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.81-84
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• 2005

We suggest flux quantum-based mechanism for force realization in the sub-pico-Newton range. By controlling the number of flux quantum in a superconducting ring, a force can be created as an integer multiple of a constant force step. For a 50 nm-thick Nb ring with the inner and outer radii of $5{\mu}m\;and\;10{\mu}m$, respectively, the force step is estimated to be 165 fN, assuming the magnetic field gradient of 10 T/m. We also estimated a maximum force limit to be $1\sim2$ pN.