• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.153-153
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• 2010

p-i-n 형 비정질 실리콘 박막 태양전지에서 p층은 창물질(window material)로서 전기 전도도가 크고, 빛 흡수가 적어야한다. p층의 두께가 얇으면 p층 전체가 depletion layer가 되고 충분한 diffusion potential을 얻을 수 없어 open-circuit voltage ($V_{oc}$)가 작아진다. 반대로 p층 두께가 두꺼워지면 빛 흡수가 증가하고, 표면 재결합이 문제가 되어 변환효율이 감소한다. 밴드갭이 큰 물질로 창층을 제작하게 되면 보다 짧은 파장의 입사광이 직접 i층을 비추므로 Short-circuit current ($I_{sc}$) 와 fill factor를 증가시킬 수 있다. 하여 본 연구에서는 기존의 창층으로 사용되는 Boron을 doping한 p-type a-Si:H 대신에 $N_2O$를 첨가한 p-type a-$SiO_x$:H의 $N_2O$ flow rate에 따른 밴드갭의 변화에 관한 연구를 수행하였다. p-type a-$SiO_x$:H Layer는 $SiH_4$, $H_2$, $N_2O$, $B_2H_6$ 가스를 혼합하여 증착하게 되는데 $SiH_4$, 가스와 $H_2$ 가스의 혼합비는 1:20, $B_2H_6$ 농도는 0.5%로 고정 하였으며 $N_2O$의 flow rate을 가변하며 증착하였다. $N_2O$의 가변조건은 5에서 50sccm으로 가변하여 증착하며 일반적으로 사용되는 RF-PECVD (13.56MHz)를 이용하였고 증착 온도는 175도, 전극간의 거리는 40mm, 파워와 압력은 30W, 700mTorr로 고정하여 진행하였다. 전기적 특성을 알아보기 위해 eagle 2000 Glass를 사용하였고 구조적 특성은 p-type wafer를 사용하여 각각 대략 200nm의 두께로 증착하였다. 증착 두께는 Ellipsometry를 이용하였으며 전기 전도도는 Agilent사의 4156c를 구조적특성은 FT-IR을 사용하여 측정하였다. Conductivity(${\sigma}_d$)는 $N_2O$가 증가함에 따라 $8.73\;{\times}\;10^{-6}$에서 $5.06\;{\times}\;10^{-7}$으로 감소하였고 optical bandgap ($E_{opt}$)은 1.71eV에서 2.0eV로 증가함을 알 수 있었다. 또한 reflective index(n)의 경우는 4.32에서 3.52로 감소함을 나타내었다. 기존의 p-type a-Si:H에 비해 상당한 $E_{opt}$을 가지므로 빛 흡수에 의한 손실을 줄임으로서 $V_oc$를 향상 시킬 수 있으며 동시에 짧은 파장에서의 입사광이 직접 i층을 비추므로 $I_{sc}$와 FF를 향상 시킬 수 있으리라 예상된다. 다소 낮은 전도도만 개선한다면 고효율의 박막 태양전지를 제작 할 수 있을 것으로 기대된다.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.1
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• pp.56-63
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• 2004

Exact solutions are presented for the free vibration and buckling of rectangular plates haying two opposite edges ( x=0 and a) simply supported and the other two ( y=0 and b) clamped, with the simply supported edges subjected to a linearly varying normal stress $\sigma$$_{x}$=- $N_{0}$[1-a(y/b)]/h, where h is the plate thickness. By assuming the transverse displacement ( w) to vary as sin(m$\pi$x/a), the governing partial differential equation of motion is reduced to an ordinary differential equation in y with variable coefficients. for which an exact solution is obtained as a power series (the method of Frobenius). Applying the clamped boundary conditions at y=0 and byields the frequency determinant. Buckling loads arise as the frequencies approach zero. A careful study of the convergence of the power series is made. Buckling loads are determined for loading parameters a= 0, 0.5, 1, 1.5. 2, for which a=2 is a pure in-plane bending moment. Comparisons are made with published buckling loads for a= 0, 1, 2 obtained by the method of integration of the differential equation (a=0) or the method of energy (a=1, 2). Novel results are presented for the free vibration frequencies of rectangular plates with aspect ratios a/b =0.5, 1, 2 when a=2, with load intensities $N_{0}$ / $N_{cr}$ =0, 0.5, 0.8, 0.95, 1. where $N_{cr}$ is the critical buckling load of the plate. Contour plots of buckling and free vibration mode shapes ate also shown.shown.

• Korean Journal of Materials Research
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• v.9 no.10
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• pp.1006-1011
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• 1999

B-doped hydrogenated amorphous silicon carbide (a-SiC:H) thin films were prepared by plasma-enhanced chemical-vapor deposition in a gas mixture of $SiH_4$, $CH_4$ and $B_2H_6$. Microstructures and chemical properties of a-SiC:H films grown with varing the volume ratio of $CH_4$ to $SiH_4$ were characterized with various analysis methods including scanning electron microscopy(SEM), X-ray diffractometry(XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy. X-ray photoelectron spectroscopy(XPS), UV absorption spectroscopy and photoconductivity measurements. While Si:H films grown without $CH_4$ showed amorphous state, the addition of $CH_4$ during deposition enhanced the development of a microcrystalline phase. By introducing C atoms into the film, Si-Si and Si--$\textrm{H}_{n}$ bonds of a -Si:H films were gradually replaced by Si-C, C-C, and Si--$\textrm{C}_{n}\textrm{H}_{m}$ bonds. Consequently, the electrical resistivity and optical bandgap of a-SiC:H films were increased with the C concentration in the film.

• International Journal of Oral Biology
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• v.41 no.3
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• pp.141-147
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• 2016

Reactive oxygen species (ROS) and nitrogen species (RNS) are both important signaling molecules involved in pain transmission in the dorsal horn of the spinal cord. Xanthine oxidase (XO) is a well-known enzyme for the generation of superoxide anions ($O_2^{\bullet-}$), while S-nitroso-N-acetyl-DL-penicillamine (SNAP) is a representative nitric oxide (NO) donor. In this study, we used patch clamp recording in spinal slices of rats to investigate the effects of $O_2^{\bullet-}$ and NO on the excitability of substantia gelatinosa (SG) neurons. We also used confocal scanning laser microscopy to measure XO- and SNAP-induced ROS and RNS production in live slices. We observed that the ROS level increased during the perfusion of xanthine and xanthine oxidase (X/XO) compound and SNAP after the loading of 2',7'-dichlorofluorescin diacetate ($H_2DCF-DA$), which is an indicator of intracellular ROS and RNS. Application of ROS donors such as X/XO, ${\beta}-nicotinamide$ adenine dinucleotide phosphate (NADPH), and 3-morpholinosydnomimine (SIN-1) induced a membrane depolarization and inward currents. SNAP, an RNS donor, also induced membrane depolarization and inward currents. X/XO-induced inward currents were significantly decreased by pretreatment with phenyl N-tert-butylnitrone (PBN; nonspecific ROS and RNS scavenger) and manganese(III) tetrakis(4-benzoic acid) porphyrin (MnTBAP; superoxide dismutase mimetics). Nitro-L-arginine methyl ester (NAME; NO scavenger) also slightly decreased X/XO-induced inward currents, suggesting that X/XO-induced responses can be involved in the generation of peroxynitrite ($ONOO^-$). Our data suggest that elevated ROS, especially $O_2^{\bullet-}$, NO and $ONOO^-$, in the spinal cord can increase the excitability of the SG neurons related to pain transmission.

• Carbon letters
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• v.11 no.4
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• pp.336-342
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• 2010

Different oxidation treatments on CNTs using diluted 4.0 M $H_2SO_4$ solution at room temperature and or at $90^{\circ}C$ reflux conditions were investigated to elucidate the physical and chemical changes occurring on the treated CNTs, which might have significant effects on their performance as catalyst supports in PEM fuel cells. Raman spectroscopy, X-ray diffraction and transmission electron microscope analyses were made for the acid treated CNTs to determine the particle size and distribution of the CNT-supported Pt-Ru nanoparticles. These CNT-supported Pt-based nanoparticles were then employed as anode catalysts in PEMFC to investigate their catalytic activity and single-cell performance towards $H_2$ oxidation. Based on PEMFC performance results, refluxed Pt-Ru/CNT catalysts prepared using CNTs treated at $90^{\circ}C$ for 0.5 h as anode have shown better catalytic activity and PEMFC polarization performance than those of the commercially available Pt-Ru/C catalyst from ETEK and other Pt-Ru/CNT catalysts developed using raw CNT, thus demonstrating the importance of acid treatment in improving and optimizing the surface properties of catalyst support.

• Journal of Ceramic Processing Research
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• v.13 no.spc2
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• pp.270-273
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• 2012

x mol% (x = 0 ~ 20) Na2CO3 excess Bi2.5Na3.5Nb5O18 (BNN) particles were synthesized using molten salt as a flux. The secondary phases were observed at stoichiometric ratio of BNN precursors and their intensity decreased with increasing Na contents. The results of SEM images showed that all particles existed in a platelet shape and the particle increased in size with higher increasing Na contents. Plate-like NaNbO3 particles were developed using BNN precursor obtained by a topochemical microcrystal conversion. XRD analysis of NaNbO3 particles showed that a single perovskite phase and the intensity of (h00) peaks increased with increasing Na contents in BNN precursor. SEM images showed that the size of plate-like NaNbO3 was significantly changed by controlling Na contents in BNN precursors.

• Structural Engineering and Mechanics
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• v.16 no.1
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• pp.35-46
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• 2003

The histories and distributions of dynamic stresses in an orthotropic hollow cylinder under sinusoidal impact load are obtained by making use of eigenfunction expansion method in this paper. Dynamic equations for axially symmetric orthotropic problem are founded and results are carried out for a practical example in which an orthotropic hollow cylinder is in initially at rest and subjected to a dynamic interior pressure $p(t)=-{\sigma}_0(sin{\alpha}t+1)$. The features of the solution appear the propagation of the cylindrical waves. The other hand, a dynamic finite element solution for the same problem is also got by making use of structural software (ABAQUS) program. Comparing theoretical solution with finite element solution, it can be found that two kinds of results obtained by two different solving methods are suitably approached. Thus, it is further concluded that the method and computing process of the theoretical solution are effective and accurate.

• Transactions of the Korean hydrogen and new energy society
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• v.6 no.1
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• pp.17-22
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• 1995

Thermally evaporated Pd films on substrate were hydrogenated upto 1 bar of hydrogen gas at room temperature. Temperature dependence hange of electrical resistivity on Pd films is examined in the thickness range between $60{\AA}$ and $990{\AA}$. Resistivity of Pd is fitted well with Bloch-$Gr{\ddot{u}}neisen$ formula. Debye temperatures of Pd films are about 254 K, which are 20 K lower than that of bulk Pd. Debye temperature is not sensitive to film thickness change. Temperature of substrate during evaporation changes temperature dependence of resistivity of films much. Optical phonon contribution increases with decreasing temperature of PdHx.

• 한국생물공학회:학술대회논문집
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• 2002.04a
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• pp.30-33
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• 2002

We have shown that it is possible to form a fibrilar network of fibronectin on a polyelectrolyte polymer film whose dimensions are similar to those reported on the extra cellular matrix. The fibronectin network was observed to form only when the charge density of the polymer was in excess of the natural charge density of the cell wall. Furthermore, the self-organized fibronectin layer was much thicker than the polymer film, indicating that long ranged interaction may playa key role in the assembly process. It is therefore important to understand the structure of the polymer layer/protein interface. Here we report on a neutron reflectivity study where we explore the structure of the polyelectrolyte layer, in this case sulfonated polystyrene (PSSx,), with varying degree of sulfonation (x<30%), as a function of sulfur content and counter ion concentration. These results are then correlated with systemic study of the adsorption and the multilayer formation of fibronectin as a function of incubation time for various sulfonation levels of $PSSx.^1$

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.317.1-317.1
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• 2013

유기 태양전지는 다른 무기계 태양전지에 비해 물질 자체의 쉬운 가공성과 유연한 특성으로 차세대 플렉시블 태양전지로 각광받고 있지만 상대적으로 짧은 수명으로 상용화에 걸림돌이 되고 있다. 현재까지 알려진 유기 태양전지의 짧은 수명의 원인으로는 수분과 산소에 의한 광활성층의 화학적 열화 및 표면의 변화, 전극의 열화, 전자-전공 수송층의 흡습현상 등이 있다 [1]. 본 연구에서는 이러한 이론적인 열화 메커니즘에 기초하여 일정한 수분과 산소 분위기에서 각 단위층들이 열화되는 현상을 광학적, 화학적 분석을 통해 짧은 수명의 원인을 밝혀내고자 한다. 유기 태양전지의 가혹시험은 $85^{\circ}C$의 온도와 85%의 습도 조건에서 이뤄졌으며, 가혹시간에 따른 열화현상 비교를 위해 0, 50, 100, 250, 500 h 동안 시험을 진행하였다. C-O, C=O 결합 형성에 의한 광활성층의 ${\pi}$공액의 변형은 FT-IR(fourier transform infrared spectroscopy)과 XRD (X-ray diffraction) 측정을 통해 분석하였고 변화된 표면 형상은 FE-SEM (field emission scanning electron microscopy) 측정을 통해 관찰하였다.