• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.3
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• pp.248-252
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• 2005

The effects of electric field strength and mechanical compressive stress on the displacement of multilayered ceramic actuator, stacked alternatively 0.2 (PbM $n_{1}$3/N $b_{2}$3/ $O_3$)-0.8(PbZ $r_{0.475}$ $Ti_{0.525}$ $O_3$) ceramic thin films and 70Ag-30Pd electrodes were investigated. Because the actuators were designed to stack ceramic layer and electrode layer alternatively, the ceramic-electrode interfaces may act as a resistance to motion of domain wall. so the polarization and strain were affected by the amount of 180$^{\circ}$domain, electric field strength and mechanical compressive stress. Consequently, the change of polarization, displacement with respect to field strength, and mechanical compressive stress were likely to be caused by readiness of the domain wall movement around the ceramic-electrode interfaces.ces.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.251-254
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• 2001

This paper describes an efficiency improvement of buried contact solar cell (BSCS) with a structure of MgF$_2$/CeO$_2$/Ag/Cu/Ni grid/n$^{+}$ emitter/p-type Si base/p$^{+}$/Al. Theoretical and experimental investigations were performed on a double layer antireflection (DLAR) coating of MgF$_2$/CeO$_2$. We investigated CeO$_2$ films as an AR layer because they have a proper refractive index of 2.46 and demonstrate the same lattice constant as Si substrate. An optimized DLAR coating shewed a reflectance as low as 2.04 % in the wavelengths ranged from 0.4 ${\mu}{\textrm}{m}$ to 1.1 ${\mu}{\textrm}{m}$. BCSC cell efficiency was improved from 16.2 % without any AR coating to 19.9 % by employing DLAR coatings. Further details on MgF$_2$/CeO$_2$ DLAR coatings on the BCSC cells are presented in this paper.per.

• Progress in Superconductivity
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• v.10 no.2
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• pp.149-154
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• 2009

We measured and analyzed the quench development in coated conductor(CC) tapes. The CC was grown on hastelloy substrates and has an Ag protection layer. The tapes were subjected to simulated AC fault currents for quench development measurement. They were immersed in liquid nitrogen during the experiment. The quench resistance increased rapidly first, and the increase slowed down afterwards. It increased linearly with applied voltage at lower voltages, and depended less strongly on applied voltage at higher voltages. The resistance was compared with that of Au/YBCO films grown on sapphire substrates, and found to increase more monotonously than the latter. Data were analyzed quantitatively with the concept of heat transfer within the tape and the surrounding liquid nitrogen. A heat balance equation was derived and solved, taking into consideration temperature dependence of thermal parameters of the tapes. Solutions, together with values of thermal parameters taken from the literature, explained the data well. Cooling by liquid nitrogen affected the quench development considerably at lower applied voltages. Dependence on applied voltages could be also understood quantitatively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.153-153
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• 2008

최근 투명전극물질이 LCD, 박막태양전지, smart window, 유기발광소자 등에 폭넓게 이용됨에 따라 그 수요가 급격이 늘어나고 있다. 이러한 투명전극 물질로는 Al : ZnO, Ga : ZnO, $MgIn_2O_4$, $AgSbO_3$, $InGaZnO_4$, ITO, Zn:ITO 등이 있으며 이중 ITO 계 산화물은 우수한 전기적 특성을 바탕으로 이미 상용화 되어있는 상태이다. 그러나 ITO 계 산화물은 indium 의 희소성과 높은 가격 때문에 폭 넓은 분야의 상용화가 어려운 실정이며, 수소 플라즈마 분위기에 화학적으로 불안정한 특성은 Si 박막태양전지 응용에 큰 문제가 되고 있다. 이에 본 연구는 박막태양전지용 ITO 계 투명전극의 indium양을 줄이면서 화학적으로 안정하고, 전기적 특성이 향상된 박막을 제조하기 위해 combinatorial sputter를 이용하여 Zn의 도핑량을 연속적으로 변화시킨 ITO 박막을 제조하였다. 또한 광학적 전기적 특성의 향상을 위해 vacuum, $H_2$, $O_2$ 분위기에서 열처리 후 각 박막의 특성 변화를 관찰하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.115-118
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• 2017

Highly photosensitive and wide bandgap amorphous silicon oxide (a-$SiO_x$:H) films were developed at low temperature ranges ($100{\sim}150^{\circ}C$) with employing plasma-enhanced chemical vapor deposition by optimizing $H_2/SiH_4$ gas ratio and $CO_2$ flow. Photosensitivity more than $10^5$ and wide bandgap (1.81~1.85 eV) properties were used for making the a-$SiO_x$:H thin film solar cells, which exhibited a high open circuit voltage of 0.987 V at the substrate temperature of $100^{\circ}C$. In addition, a power conversion efficiency of 6.87% for the cell could be improved up to 7.77% by employing a new n-type nc-$SiO_x$:H/ZnO:Al/Ag triple back-reflector that offers better short circuit currents in the thin film photovoltaic devices.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.166.1-166.1
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• 2014

We have controlled the graphene surface in two ways to improve the device performance of optoelectronics based on graphene transparent conductive films. We controlled multilayer graphene (MLG) work function and localized surface plasmon resonance wavelength using a silver nanoparticles formed on graphene surface. Graphene substrates were prepared using a chemical vapor deposition and transfer process. Various size of silver nanoparticles were prepared using a thermal evaporator and post annealing process on graphene surface. Silver nanoparticles were confirmed by using scanning electron microscopy (SEM). Work functions of graphene surface with various sizes of Ag nanoparticles were measured using ultraviolet photoelectron spectroscopy (UPS). The result shows that the work functions of MLG could be controlled from 4.39 eV to 4.55 eV by coating different amounts of silver nanoparticles while minimal changes in the sheet resistance and transmittance. Also the Localized surface plasmon resonance (LSPR) wavelength was investigated according to various sizes of silver nanoparticles. LSPR wavelength was measured using the absorbance spectrum, and we confirmed that the resonance wavelength could be controlled from 396nm to 425nm according to the size of silver nanoparticles on graphene surface. To confirm improvement of the device performance, we fabricated the organic solar cell based on MLG electrode. The results show that the work function and plasmon resonance wavelength could be controlled to improve the performance of optoelectronics device.

• Korean Journal of Materials Research
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• v.13 no.10
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• pp.663-667
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• 2003

The effects of paste materials on field emission properties in a carbon nanotube(CNT) cathode were investigated for high-efficient field emission displays. The major components in CNT paste for screen printing were a metallic Ag-paste, a dielectric glass-frit and CNT ink. The emission current from the cathode by an electron tunneling effect increased with an increase in the dielectric material fraction in the CNT paste, which is related to an increase of field enhancement factor in Fowler-Nordheim equation. The surface treatment used, after soft baking of the screen-printed CNT films, greatly affected the decrease in the turn-on field in CNT cathode and the uniformity of emission sites over the entire CNT film area.

• Journal of the Korean institute of surface engineering
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• v.40 no.1
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• pp.6-10
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• 2007

For low-emissivity application on window glass, coalescence of thin film silver islands is crucial for high transmittance in the visible and high reflectance in the infrared. It is well known that the underlayer affects the growth mode. In this work, the effect of the underlayer on the growth of silver films deposited by filtered cathodic vacuum arc is discussed. While a nominal 0.1 nm niobium underlayer has promoted the coalescence of silver islands, a 0.2 nm layer did not show these features. From a thermodynamic approach, Nb seeding less one monolayer is considered to reduce the surface energy between the silver atoms and $Nb/TiO_2$ surface, resulting the change of its growth from 3D islands to 2D-layer modes. If the seed layer exceeds one monolayer, however, a rougher surface is formed because the surface energy of Nb itself is superior to that of $Nb-TiO_2$. The onset of silver layer on the roughened Nb surface is required more silver.

• Carbon letters
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• v.4 no.4
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• pp.168-174
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• 2003

Silver nitrate ($AgNO_3$) powder was mixed into a reformed pitch precursor. Then, the silver-containing pitch was melt spun to form round and "C" shape fibers. A wire mesh was inserted prior to the nozzle to improve the spinnability of the silvercontaining precursor pitch. Silver particles in the carbon fibers (CFs) were detected by XRD and TEM. These tests showed that silver particles were uniformly distributed and the total amount of silver remained constant during stabilization and carbonization. Next, the silver-containing CFs were activated by steam diluted in nitrogen gas. Silver particles accelerated the activation rate, but the specific surface areas of the silver-containing ACFs were similar to those of non-silver containing ACFs at the same burn-off levels. The specific surface area of the C-shaped activated carbon fibers was larger than that of the round activated carbon fibers. The likely reason is that the surface area of a C-shaped CF is about two times larger than that of a round CF when equivalent cross-sectional areas are compared. A small amount of silver particles in the periphery of the CFs was removed during the activation, but the remainder of silver was stayed within the ACFs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.346-346
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• 2008

최근 디지털 컨버젼스에 의해서 정보 단말기 network가 디지털 기술을 기반으로 유기적으로 융 복합화 되고 있으며 BT, NT, ET, IT의 융합 기술의 필요성이 점차적으로 증대되고 있다. 이러한 환경 하에서 다양한 정보 및 서비스의 송신 및 수신이 가능한 휴대 단말기의 필요성에 부응하여 기존의 전화 기능, 카메라, DMB 이외에도 홈 네트워크, mobile internet 등 더욱 다양한 기능들이 요구되고 있다. 종래에는 수동 부품과 능동 부품의 실장을 별개로 추진했으나 최근에는 수동 및 능동 부품을 하나의 패키지 내에 실장 가능하도록 하는 3-D Integration을 추진하고 있다. 지금까지 여러 부품들을 실장 시키기 위한 공정들의 대부분은 높은 온도에서 공정이 이루어졌으나 여러 부품들을 손상 없이 집적화하고 실장하기 위해서는 저온화 공정이 필요하다. 최근 많은 저온 공정 중에서 Aerosol Deposition Method는 상온에서 세라믹 후막을 성막할 수 있어 가장 주목받고 있는 공정중의 하나이다. 본 연구에서는 3-D Integration을 실현하기 위해 이종 접합에 유리하고 상온에서 성막 공정이 이루어지는 Aerosol Deposition Method를 이용하여 금속 기판 위에 금속, 폴리머, 세라믹 후막을 성막시켰다. 기판 재료로는 Cu 기판을 사용하였으며 출발 파우더로는 Polyimide 파우더와 $Al_2O_3$ 파우더, Ag 파우더를 사용하였으며 이종 접합간의 메커니즘의 양상을 보기 위해 같은 조건에서 이종 접합간의 성막률을 비교하였으며 FE-SEM으로 미세 구조를 관찰하였다. 또한 기판의 표면 거칠기에 따른 메커니즘의 양상을 연구하였다.