• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.4
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• pp.67-72
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• 1989

Room Temperature Plasma Nitridation of silicon was investigated as a new LOCOS (local oxidation of silicon) process in order to reduce the bird's beak length. In $N_2$ plasma formed by 100kHz, 400W AC power, a thin silicon nitride film (<100${\AA}$) was uniformly grown on a silicon substrate. SEM studies showed that the nitride layer formed by this method can effectively protect the silicon from oxidation and reduce the bird's beak length to $0.2{mu}m$ when 4000${\AA}$ field oxide is grown. This is a considerable improvement comparing with 0.7${mu}m,$ the bird's beak, for the conventional LOCOS process using a thick LPCVD nitride. No appreciable crystalline defect could be found around the bird's beak with SEM cross-section afrer Secco etch. Leakage current tests were carried out on the $N^+/P^-$ well and $P^+/N^-$ well diodes formed by this new LOCOS process. The electrical tests indicate that this new process has electrical properties similar or superior to those of the conventional LOCOS process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.12
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• pp.1122-1127
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• 1998

Group II-AF_2$films such as $CaF_2$, $SrF_2$, and $BaF_2$ have been commonly used many practical applications such as silicon on insulatro(SOI), three-dimensional integrated circuits, buffer layers, and gate dielectrics in filed effect transistor. This paper presents electrical and structural properties of fluoride films as a gate dielectric layer. Conventional gate dielectric materials of TFTs like oxide group exhibited problems on high interface trap charge density($D_it$), and interface state incorporation with O-H bond created by mobile hydrogen and oxygen atoms. To overcome such problems in conventional gate insulators, we have investigated $CaF_2$ films on Si substrates. Fluoride films were deposited using a high vacuum evaporation method on the Si and glass substrate. $CaF_2$ films were preferentially grown in (200) plane direction at room temperature. We were able to achieve a minimum lattice mismatch of 0.74% between Si and $CaF_2$ films. Average roughness of $CaF_2$ films was decreased from 54.1 ${\AA}$ to 8.40 ${\AA}$ as temperature increased form RT and $300^{\circ}C$. Well fabricated MIM device showed breakdown electric field of 1.27 MV/cm and low leakage current of $10^{-10}$ A/$cm^2$. Interface trap charge density between $CaF_2$ film and Si substrate was as low as $1.8{\times}10^{11}cm^{-2}eV^{-1}$.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.118-120
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• 2001

The $0.96MgTiO_3-0.04SrTiO_3+xLa(0{\sim}1.0wt%)$ ceramics were prepared by conventional mixed oxide method. The structural properties of $0.96MgTiO_3-0.04SrTiO_3+xLa(0{\sim}1.0wt%)$ ceramics with sintering temperature were investigated by the XRD and SEM. From the X-ray diffraction patterns, it was found that the perovskite $SrTiO_3$ and ilmenite $MgTiO_3$ structures were coexisted in the $0.96MgTiO_3-0.04SrTiO_3$ ceramics. The second phase of $Sr_{0.5}LaTi_2O_6$ was shown with addition of the $La_2O_3$. The dielectric constant(${\varepsilon}_r$), $Q{\times}f$ value and the temperature coefficient of the $0.96MgTiO_3-0.04SrTiO_3+0.2La$ ceramics were 21. 41, 39991, $-3.3ppm/^{\circ}C$, respectively.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.78.1-78.1
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• 2010

The metal-supported solid oxide fuel cell (SOFC) was studied. Hydrocarbon fueled operation is necessary to make SOFC system. Different operating characteristics for metal-supported SOFC are used than for conventional ones as hydrocarbon fueled operation. Metal-supported SOFC was successfully fabricated by a high temperature sinter-joining method and the cathode was in-situ sintered. Synthetic gas, which is compounded as the diesel reformate gas composition and low hydrocarbons was completely removed by the diesel reformer. Metal-supported SOFC with synthetic gas was operated and evaluated and its characteristics analyzed. Button cell and $5{\times}5cm^2$ single stack were mainly operated and analyzed. Long-term operation using diesel reformate shows degradation, and degradation analysis was completed in the view of metal oxidation. Solution to increase stability of long-term operation was tried in the way of materials and operating conditions. Finally, $5{\times}5cm^2$ metal-supported single stack using synthetic gas was operated for 1000 hours under the modified condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.417-417
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• 2009

Although a transparent conductive film (TCF) belongs to essential supporting materials for many device applications such as touch screens, flat panel displays, and sensors, a conventional transparent conductive material, indium-tin oxide (ITO), suffers from considerable drawback because the price of indium has soared since 2001. Despite a recent falloff, a demand of ITO is expected to increase sharply in the future due to the trend of flat panel display technologies toward flexible, paper-like features. There have been recently extensive studies to replace ITO with new materials, in particular, carbon nanotubes (CNTs) since CNTs possess excellent properties such as flexibility, electrical conductivity, optical transparency, mechanical strength, etc., which are prerequisite to TCFs. This study fabricated TCFs with single-walled carbon nanotubes (SWCNTs) produced by arc discharge. The SWCNTs were dispersed in water with a surfactant of sodium dodecyl benzene sulfonate (NaDDBS) under sonication. Carbon black and fullerene nanoparticles were added to the SWCNT-dispersed solution to enhance contact resistance between CNTs. TCFs were manufactured by a filtration and transfer method. TCFs added with carbon black and fullerene nanoparticles were characterized by scanning electron microscopy (SEM), UV-vis spectroscopy (optical transmittance), and four-point probe measurement (sheet resistance).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.188-189
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• 2009

In this study, in order to develop excellent lead-free composition ceramics for piezoelectric transformer, $(K_4CuNb_8O_{23})$ added $(K_{0.5}Na_{0.5})(Nb_{0.96}Sb_{0.04})O_3$ ceramics were fabricated using conventional mixed oxide method and their piezoelectric and dielectric properties were investigated as a function of the amount of KCN addition. With increasing the amount of KCN addition, density and mechanical quality factor(Qm), electromechanical coupling factor (Kp) were increased up to 1.2mol% and then decreased. At the 1.2mol% KCN added specimen, mechanical quality factor (Qm), electromechanical coupling factor (Kp), density and dielectric constant (${\varepsilon}r$) showed the optimal values of 781, 0.445, $4.42g/cm^3$ and 443, respectively, for piezoelectric transformer application.

• Journal of Korea Society of Digital Industry and Information Management
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• v.5 no.2
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• pp.77-85
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• 2009

In this paper, we propose data format for smell, taste, touch with speech and vision which can be transmitted and implement a floral scent detection and recognition system. We provide representation method of data of smell, taste, and touch. Also, proposed floral scent recognition system consists of three module such as floral scent acquisition module using Metal Oxide Semiconductor (MOS) sensor array, entropy-based floral scent detection module, and floral scent recognition module using correlation coefficients. The proposed system calculates correlation coefficients of the individual sensor between feature vector(16 sensors) from floral scent input point until the stable region and 12 types of reference models. Then, this system selects the floral scent with the maximum similarity to the calculated average of individual correlation coefficients. To evaluate the floral scent recognition system using correlation coefficients, we implemented an individual floral scent recognition system using K-NN with PCA and LDA that are generally used in conventional electronic noses. In the experimental results, the proposed system performs approximately 95.7% average recognition rate.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.5
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• pp.108-115
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• 2014

In this study, experimental approaching method was applied under and single-cylinder engine to research the performance of direct needle-driven piezo injector (DPI) for CR direct-injection. As key-point factor of this DPI that relies on direct-acting operating of injector needle, unlike conventional hydraulic-servo, its nozzle needle can be directly driven by piezo actuator. Thus, effect of direct-acting injection of DPI on diesel combustion and emission characteristics was investigated under common-rail single-cylinder direct-injection engine, equipped with three different driving mechanism, including indirect-acting solenoid, piezo and DPI system. As main results, it found that a direct-acting piezo injector has higher of IMEP. And it has higher heat release rate during premixed combustion and mixing controlled combustion phase due to its higher heat release, even though nitrogen oxide (NOx) formations were increased slightly.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1465-1466
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• 2011

We have studied structural and electrical properties of $(Na_{0.5}K_{0.5})NbO_3$ ceramics addition with $BiTiO_3$. The $(Na_{0.5}K_{0.5})NbO_3-BiTiO_3$ ceramics were fabricated by the conventional mixed oxide method, their dielectric and piezoelectric properties were investigated with the variations of additvie amount $BiTiO_3$. At the sintering temperature of $1130^{\circ}C$, the density, dielectric constant, grain size of 0.05mol% $BiTiO_3$ specimen showed the values of 4.69 g/$cm^3$, 898 and $24.8{\mu}m$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.1
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• pp.144-151
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• 2010

The shadowing effects lead to the serious power losses of the PV module. The shadowing effects are caused by several factors such as leafs, dust, antenna and clouds. The dye-sensitized solar cells are more economical than the conventional silicon solar cell that's why the dye-sensitized solar cells are recently focused on. We carried out research on the efficiency of the dye-sensitized solar cell depending on the level of shadow changing the formula of the circuit. The research on the efficiency of the large dye-sensitized solar cell depending on the level of shadow focused on commercialization was carried out. As the results, it is known that the series and parallel connection method is the best choice for the least losses of PV module assemblies. It is especially known that one more series connection is the best choice for the least losses about shadowing effects and current losses in the series and parallel connection.