• Tribology and Lubricants
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• v.21 no.5
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• pp.209-215
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• 2005

Nano/micro friction with the contact area was studied on Si-wafer (100) and diamond-like carbon (DLC) film. Borosilicate balls of radii $0.32{\mu}m,\;0.5{\mu}m,\;1.25{\mu}m\;and\;2.5{\mu}m$ mounted on the top of AFM tip (NPS) were used for nano-scale contact and Soda Lime glass balls of radii 0.25mm, 0.5mm, 1mm were used for micro-scale contact. At nano-scale, the friction between ball and surface was measured with the applied normal load using an atomic force microscope (AFM), and at micro scale it was measured using ball-on flat type micro-tribotester. All the experiments were conducted at controlled conditions of temperature $(24\pm1^{\circ}C)$ and humidity $(45\pm5\%)$. Friction was measured as a function of applied normal load in the range of 0-160nN at nano scale and in the range of $1000{\mu}N,\; 1500{\mu}N,\;3000{\mu}N\;and\;4800{\mu}N$ at micro scale. Results showed that the friction at nano scale increased with the applied normal load and ball size for both kinds of samples. Similar behavior of friction with the applied normal load and ball size was observed for Si-wafer at micro scale. However, for DLC friction decreased with the ball size. This difference of in behavior of friction in DLC nano- and microscale was attribute to the difference in the operating mechanisms. The evidence of the operating mechanisms at micro-scale were observed using scanning electron microscope (SEM). At micro-scale, solid-solid adhesion was dominant in Silicon-wafer, while plowing in DLC. Contrary to the nano scale that shows almost a wear-less situation, wear was prominent at micro-scale. At nano- and micro-scale, effect of contact area on the friction was discussed with the different applied normal load and ball size.

• Journal of the Korean Ceramic Society
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• v.51 no.5
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• pp.435-441
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• 2014

Silicon carbide-based ceramics and their composites have been studied for application to fusion and advanced fission energy systems. For fission reactors, $SiC_f$/SiC composites can be applied to core structural materials. Multilayered SiC composite fuel cladding, owing to its superior high temperature strength and low hydrogen generation under severe accident conditions, is a candidate for the replacement of zirconium alloy cladding. The SiC composite cladding has to retain its mechanical properties and original structure under the inner pressure caused by fission products; as such it can be applied as a cladding in fission reactor. A hoop strength test using an expandable polyurethane plug was designed in order to evaluate the mechanical properties of the fuel cladding. In this paper, a hoop strength test of the multilayered SiC composite tube for nuclear fuel cladding was simulated using FEA. The stress caused by the plug was distributed nonuniformly because of the friction coefficient difference between the inner surface of the tube and the plug. Hoop stress and shear stress at the tube was evaluated and the relationship between the concentrated stress at the inner layer of the tube and the fracture behavior of the tube was investigated.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.73.1-73.1
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• 2010

태양광 시장은 세계적인 금융 위기 속에서도 점점 그 규모가 확대되고 있다. 시장의 규모가 확대되고 있음에도 불구하고 금융 위기를 겪으면서 생산자 중심의 시장에서 수요자 중심의 시장으로 바뀌게 되었다. 이에 따라 더 적은 비용으로 높은 출력의 제품만이 경쟁력을 가지게 됨으로써 효율이 더욱 이슈화되었다. 여러 태양전지 중 가장 점유율이 높은 결정질 태양전지는 일반적인 양산 공정만으로 효율을 높이는데 한계가 있으므로 selective emitter, back contact, light induced plating 등의 새로운 공정을 도입하여 효율을 높이려는 경향이 나타나고 있다. 본 연구에서는, ALD 장치를 사용하여 결정질 태양전지의 후면을 passivation 함으로써 효율을 높이는 방법을 모색하였다. 부동화 층으로는 $Al_2O_3$를 사용하였으며 셀을 제조하여 평가하였다. 실험방법은 p-type의 웨이퍼를 이용하여 습식으로 texturing 후 $POCl_3$ 용액으로 p-n junction을 형성하였고 anti-reflection 막인 SiNx는 PECVD를 사용하여 R.I 2.05, 80nm 두께로 증착하였다. 그런 다음 후면의 n+ layer를 제거하기 위하여 SiNx에 영향을 미치지 않는 용액을 사용하여 후면을 식각하였다. BSF 층은 screen printer로 Al paste를 printing하여 형성하였고 Al etching용액으로 여분의 Al제거한 후 ALD 장치를 이용하여 $Al_2O_3$를 증착하였다. 마지막으로 전극을 형성한 후 laser로 isolation하여 효율을 평가하였다.

• Bulletin of the Korean Chemical Society
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• v.26 no.11
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• pp.1653-1668
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• 2005

Assembly of hybrid mesophases through the combination of amphiphilic block copolymers, acting as structuredirecting agents, and silicon sources using low acid catalyst concentration regimes is a versatile strategy to produce large quantities of high-quality ordered large-pore mesoporous silicas in a very reproducible manner. Controlling structural and textural properties is proven to be straightforward at low HCl concentrations with the adjustment of synthesis gel composition and the option of adding co-structure-directing molecules. In this account, we illustrate how various types of large-pore mesoporous silica can easily be prepared in high phase purity with tailored pore dimensions and tailored level of framework interconnectivity. Silica mesophases with two-dimensional hexagonal (p6mm) and three-dimensional cubi (Fm$\overline{3}$m, Im$\overline{3}$m and Ia$\overline{3}$d) symmetries are generated in aqueous solution by employing HCl concentrations in the range of 0.1−0.5 M and polyalkylene oxide-based triblock copolymers such as Pluronic P123 $(EO_{20}-PO_{70}-EO_{20})$ and Pluronic F127 $(EO_{106}-PO_{70}-EO_{106})$. Characterizations by powder X-ray diffraction, nitrogen physisorption, and transmission electron microscopy show that the mesoporous materials all possess high specific surface areas, high pore volumes and readily tunable pore diameters in narrow distribution of sizes ranging from 4 to 12 nm. Furthermore, we discuss our recent advances achieved in order to extend widely the phase domains in which single mesostructures are formed. Emphasis is put on the first synthetic product phase diagrams obtained in $SiO_2$-triblock copolymer-BuOH-$H_2O$ systems, with tuning amounts of butanol and silica source correspondingly. It is expected that the extended phase domains will allow designed synthesis of mesoporous silicas with targeted characteristics, offering vast prospects for future applications.

• Clean Technology
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• v.7 no.3
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• pp.203-214
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• 2001

A silicon oxide cleaning characteristic and its mechanism were studied in RF plasma cleaning system with various gases such as $CHF_3$, $CF_4$, Argon, oxygen and mixing gas. The experimental parameters - working pressure (100 mTorr), RF power (300 W, 500 W), electrode distance (5cm, 8cm, 11.5cm), cleaning time (90, 180 seconds), gas flow (50 sccm) were fixed to compare cleaning efficiency by gas types. The results were as follows. First, the argon plasma is retaining only physical sputtering effect and etch rate was low. Second, the oxygen plasma showed good cleaning efficiency in electrode distace of 5cm, 300W, 180secs, but surface roughness increased. Third, $CF_4$ Plasma could get the best cleaning efficiency. Fourth, $CHF_3$ plasma could know that addition gas that can lower the CFx/F ratio need. We could not get good cleaning efficiency in case of added argon to $CHF_3$. But, we could get good cleaning efficiency in case added oxygen.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.603-606
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• 2005

In this paper, the formation and thermal stability of Ni-silicide using Ni-Pd alloys is studied for ultra shallow S/D junction of nano-scale CMOSFETs. There are no different effects when Ni-Pd is used in single structure and TiN capping structure. But, in case of Cobalt interlayer structure, it was found that Pure Ni had lower sheet resistance than Ni-Pd, because of a thick silicide. Also, Ni-Pd has merits that surface of silicide and interface between silicide and silicon have a good morphology characteristics. As a result, Ni-Pd is an optimal candidate for shallow S/D junction when cobalt is used for thermal stability.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.11
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• pp.1-7
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• 2008

In this work, a two dimensional, self-consistent Poisson-$Schr{\ddot{o}}dinger$ solver has been implemented to study C-V characteristics in nanometer scale MuGFETs with considering quantum effects. The quantum-mechanical effects on gate-channel capacitance for different device dimension and gate configurations of nanometer scale MuGFETs have been analyzed. It has been found that 4he gate-channel capacitance per unit gate area is increased as the device dimension decreases. For different gate configurations, the gate-channel capacitance is decreased with increase of effective gate number. Those resu1ts have been explained by the distribution profile of electron concentration in the silicon surface and inversion capacitance. The length of inversion-layer centroid has been calculated from inversion capacitance with device dimension and gate configurations.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.2
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• pp.65-69
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• 2011

The $Tio_2$ films were prepared on glass, silicon and quartz substrate at different temperature by radio frequency reactive magnetron sputtering under different flow ratios of Ar and O2 gases. The films were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), atomic force microscope (AFM) and UV-VIS spectrophotometer. Only the anatase phase was observed in films and their diffaction peaks increased with temprature of substrate. The size of crystallites decreased with higher concentration of oxygen. Refractive index and optical absorption of thin films decreased with higher concentration of oxygen. The thin films which have good transmittance spectra and smooth surface, deposited in the sputtering ambient with 10 % of $O_2$ at the temperature from $400{\circ}C$ to $300{\circ}C$.

• Korean Journal of Materials Research
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• v.19 no.2
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• pp.73-78
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• 2009

This study investigated the dependence of the various sputtering conditions (Ar pressure: $2{\sim}10\;mTorr$, Power: $50{\sim}150\;W$) and thickness ($50{\sim}1200\;nm$) of Si thin film on the electrochemical properties, microstructural properties and the capacity fading of a Si thin film anode. A Si layer and a Ti buffer layer were deposited on Copper foil by RF-magnetron sputtering. At 10 mTorr, the 50 W sample showed the best capacity of 3323 mAh/g, while the 100 W sample showed the best capacity retention of 91.7%, also at 10 mTorr. The initial capacities and capacity retention in the samples apart from the 50W sample at 10 mTorr were enhanced as the Ar pressure and power increased. This was considered to be related to the change of the microstructure and the surface morphology by various sputtering conditions. In addition, thinner Si film anodes showed better cycling performance. This phenomenon is caused by the structural stress and peeling off of the Si layer by the high volume change of Si during the charge/discharge process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.235-235
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• 2009

This paper describes the influence of a polycrystalline (poly) 3C-SiC buffer layer on the surface acoustic wave (SAW) properties of poly aluminum nitride (AlN) thin films by comparing the center frequency, insertion loss, the electromechanical coupling coefficient ($k^2$), andthetemperaturecoefficientoffrequency(TCF) of an IDT/AlN/3C-SiC structure with those of an IDT/AlN/Si structure, The poly-AlN thin films with an (0002)-preferred orientation were deposited on a silicon (Si) substrate using a pulsed reactive magnetron sputtering system. Results show that the insertion loss (21.92 dB) and TCF (-18 ppm/$^{\circ}C$) of the IDT/AlN/3C-SiC structure were improved by a closely matched coefficient of thermal expansion (CTE) and small lattice mismatch (1 %) between the AlN and 3C-SiC. However, a drawback is that the $k^2(0.79%)$ and SAW velocity(5020m/s) of the AlN/3C-SiC SAW device were reduced by appearing in some non-(0002)AlN planes such as the (10 $\bar{1}$ 2) and (10 $\bar{1}$ 3) AlN planes in the AlN/SiC film. Although disadvantages were shown to exist, the use of the AlN/3C-SiC structure for SAW applications at high temperatures is possible. The characteristics of the AlN thin films were also evaluated using FT-IR spectra, XRD, and AFM images.