• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.911-914
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• 2003

The non-contact laser measurement system what can be used for the vibration analysis of structures is discussed. There are few systems using laser speckle interferometer for vibration analysis. One of these systems is the Electronic Speckle Pattern Interferometer (ESPI). With ESPI system, one can obtain the vibration mode shape qualitatively and the maximum vibration amplitude quantitatively of the structure at each resonance frequency. In this paper, the phase-shifting ESPI system with stroboscopic illumination for measuring vibration mode shapes is constructed and the operating software is programmed. The results are compared with that of commercial ESPI system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.10
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• pp.865-870
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• 2003

The MFIS (Metal-Ferroelectric-Insulator-Semiconductor) capacitors were fabricated using a metalorganic decomposition method. Thin layers of CeO$_2$ were deposited as a buffer layer on Si substrate and BLT thin films were used as a ferroelectric layer. The electrical and structural properties of the MFIS structure were investigated. X -ray diffraction was used to determine the phase of the BLT thin films and the quality of the CeO$_2$ layer. The morphology of films and the interface structures of the BLT and the CeO$_2$ layers were investigated by scanning electron microscopy. The width of the memory window in the C-V curves for the MFIS structure is 2.82 V. The experimental results show that the BLT-based MFIS structure is suitable for non-volatile memory FETs with large memory window.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04b
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• pp.125-128
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• 2004

In this paper, a novel processing technique for fabrication of high-temperature MEMS based on polymer-derived SiCN microstructures is described. PDMS molds are fabricated on SU-8 photoresist using standard UV-photolithographic processes. Liquid precursors are injected into the PDMS mold. And then, the resulting solid polymer structures are crosslinked under isostatic pressure, and pyrolyzed to form a ceramic capable of withstanding over $1500^{\circ}C$. These fabricated SiCN structures would be applied for high-temperature applications, such as heat exchanger and combustion chamber.

• Advances in concrete construction
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• v.9 no.4
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• pp.407-412
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• 2020

Due to the influence of nonlinearity and time-variation, it is difficult to establish an accurate model of concrete frame structures that adopt active controllers. Fuzzy theory is a relatively appropriate method but susceptible to human subjective experience to decrease the performance. To guarantee the stability of multi-time delays complex system with multi-interconnections, a delay-dependent criterion of evolved design is proposed in this paper. Based on this criterion, the sector nonlinearity which converts the nonlinear model to multiple rule base of the linear model and a new sufficient condition to guarantee the asymptotic stability via Lyapunov function is implemented in terms of linear matrix inequalities (LMI). A numerical simulation for a three-layer reinforced concrete frame structure subjected to earthquakes is demonstrated that the proposed criterion is feasible for practical applications.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.105-107
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• 2002

The device characteristics and the interface electronic structures of organic light-emitting devices based on tris-(8-hydroxyquinoline)aluminum were investigated with $Al/CaF_2$, Al/LiF, and Al-only cathodes. Similar to the Al/LiF cathode, the $Al/CaF_2$ cathode greatly improved the performance of the device over Al-only cathode. However, a photoelectron spectroscopy study revealed that despite the performance improvement, the evolution of the new peaks during $Al/CaF_2$ cathode formation closely resembled those of the Al-only cathode rather than the Al/LiF cathode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.226-229
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• 2001

To achieve ZnO layer with a high resistance, a new sputtering method with a Ramp method and cycled power process mode was developed. The specific resistance of the layers was in rang of $3*10^{10}{\Omega}cm$ to $2*10^{11}{\Omega}cm$. The characteristics of. ZnO thin films changed with working pressure and Ramp method were investigated by XRD(x-ray diffractometer), and SEM (scanning electron microscopy) analyses. This paper presents calculated and measured results for structures with thin ZnO layers. Measurements of SAW properties using thin ZnO layered structures will be shown. Also presented are results on the quality of ZnO films and specifics of the deposition process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.362-365
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• 2001

The chalcogenide glasses of thin films have the superior property of photoinduced anisotrophy(PA). In this study, we observed the linear dichroism(D) using the irradiation with polarized He-Ne laser light, in the $Ag/As_{40}Ge_{10}Se_{15}S_{35}$ multi-layer. Mutilayer structures formed by alternating metal(Ag) a chalcogenide$(As_{40}Ge_{10}Se_{15}S_{35})$. Such multilayer structures have a greater sensitivity to illumination am larger dichroism in comparison the conventional double layer structure. Also new phenomena are discovered. These results will be show a capability of new method that suggested more improvement of photoinduced anisotropy property.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.3
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• pp.228-233
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• 2001

This paper presents the optimized design, fabrication and thermal characteristics of micro-heaters for thermal MEMS (micro elelctro mechanical system) applications usign SOI (Si-on-insulator) and trench structures. The micro-heater is based on a thermal measurement principle and contains for thermal isolation regions a 10㎛ thick Si 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 suing MgO as medium layer. The thermal characteristics of the micro-heater wit the SOI membrane is 280$\^{C}$ at input power 0.9W; for the SOI membrane with 10 trenches, it is 580$\^{C}$ 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.1
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• pp.21-27
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• 2000

We used the surface photovoltage spectroscopy(SPVS) for characterization of GaAs/Al\ulcornerGa\ulcornerAs multi-quantum well(MQW) structures grown by molecular beam epitaxy(MBE) method. Energy gap related transitions in GaAs and AlGaAs were observed. The Al composition(x=0.3) was determined by Sek's composition formula. Transition energies in MQW were determined using the differential surface photo-volatage spectroscopy)DSPVS) of the measured resonanced. In order to indentify the transitions, the experimentally observed energies were compared with results of the envelope function approximation for a rectangular quantum well. We have observed and interesting behavior of the temperature dependence(80K~300K) of the 11Hand 11L transition for sample.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.05a
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• pp.17-19
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• 1988

$YBa_2Cu_3O_{7-x}$ oxide superconductors were fabricated by the hot isostatic pressing (HIP). It was shown that their structures were orthorombic and constited of a single (123) phase. While as-sintered compacts had many pores, they were remarkably reduced by Hiping. The on-set and off set temperature of (123) compound sintered at $950^{\circ}C$ in oxygen and hiping at $880^{\circ}C$ were the highest and it showed 0 resistance at $90^{\circ}K$. The critical current density ($J_c$) of the above superconductor was $27A/cm^2$ and it also showed a number of twin structures, which are typical of high $T_c$ superconductor. It seemed that the low current density may be due to the many pores of starting-sintered compacts.