• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.31-39
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• 2008

To develop the MEMS cap bonding process without cavity formation, we electroplated Cu/Sn rim structures and measured the bonding characteristics for the Cu/Sn rims of $25{\sim}400{\mu}m$ width. As the effective device-mounting area ratio decreased and the failure strength ratio increased for wider Cu/Sn rim, these two properties were estimated to be optimized for the Cu/Sn rim with 150 ${\mu}m$ width. Complete bonding was accomplished at the whole interfaces of the Cu/Sn packages with the rim widths of 25 ${\mu}m$ and 50 ${\mu}m$. However, voids were observed locally at the interfaces with the rim widths larger than 100 ${\mu}m$. Such voids were formed by local non-contact between the upper and lower rims due to the surface roughness of the electroplated Sn.

• Current Photovoltaic Research
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• v.6 no.1
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• pp.21-26
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• 2018

Beside several advantages, the PV power generation as a clean energy source, is still below the supply level due to high power generation cost. Therefore, the interest in fabricating low-cost thin film solar cells is increasing continuously. $Cu_2O$, a low cost photovoltaic material, has a wide direct band gap of ~2.1 eV has along with the high theoretical energy conversion efficiency of about 20%. On the other hand, it has other benefits such as earth-abundance, low cost, non-toxic, high carrier mobility ($100cm^2/Vs$). In spite of these various advantages, the efficiency of $Cu_2O$ based solar cells is still significantly lower than the theoretical limit as reported in several literatures. One of the reasons behind the low efficiency of $Cu_2O$ solar cells can be the formation of CuO layer due to atmospheric surface oxidation of $Cu_2O$ absorber layer. In this work, atomic layer deposition method was used to remove the CuO layer that formed on $Cu_2O$ surface. First, $Cu_2O$ absorber layer was deposited by electrodeposition. On top of it buffer (ZnO) and TCO (AZO) layers were deposited by atomic layer deposition and rf-magnetron sputtering respectively. We fabricated the cells with a change in the deposition temperature of buffer layer ranging between $80^{\circ}C$ to $140^{\circ}C$. Finally, we compared the performance of fabricated solar cells, and studied the influence of buffer layer deposition temperature on $Cu_2O$ based solar cells by J-V and XPS measurements.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.1
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• pp.71-76
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• 2010

The electrorefining process, one of main processes which are composed of pyroprocess to recover the useful elements from spent fuel, and the domestic development of electrorefiner have been reviewed. The electrorefiner is composed of an anode basket containing reduced spent fuel such as uranium, transuranic and rare earth elements, and a solid cathode, which are in LiCl-KCl eutectic electrolyte. Oxidation (dissolution) reaction occurs on the anode and a pure uranium is electrochemically reduced (deposited) on the solid cathode. By application of graphite cathode, which has a self-scrapping characteristics for the uranium deposits, and a recovery of the fallen deposits by a screw conveyer, a high-throughput continuous electrorefiner with a capacity of 20 kgU/day has been developed.

• Journal of the Korean Electrochemical Society
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• v.8 no.3
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• pp.135-138
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• 2005

We investigated the electrochemical formation of a stoichiometric III-V compound semiconductor of InSb from an aqueous citric solution. Under an? optimized electrochemical condition, not like other research results, the electrodeposited InSb are satisfied exactly with the stoichiometry. Furthermore it retains the inherent characteristics of III-V compound semiconductor, InSb without heat treatment. EPMA, XPS and XRD were employed for confirmation of its composition/stoichiometry, chemical state, and crystallographic orientation, respectively.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.2
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• pp.67-72
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• 2012

In recent days, the wire width of IC is narrowed and the degree of integration of IC is increased to obtain the higher capacity of the devices in electronic industry. And then the surface quality of FCCL(Flexible Copper Clad Laminate) became increasingly important. Surface defects on FCCL are bump, scratch, dent and so on. In particular, bumps cause low reliability of the products. Even though there are bumps on the surface, if leveling characteristic of plating solution is good, it does not develop significant bump. In this study, the leveling characteristics of additives are investigated. The objective of study is to improve the leveling characteristic and reduce the surface step through additives and plating conditions. The additives in the electrodeposition bath are critical to obtain flat surface and free of defects. In order to form flat copper surface, accelerator, suppressor and leveler are added to the stock solution. The reason for the addition of leveler is planarization surface and inhibition of the formation of micro-bump. Levelers (SO(Safranin O), MV(Methylene Violet), AB(Alcian Blue), JGB(Janus Green B), DB(Diazine Black) and PVP(Polyvinyl Pyrrolidone) are used in copper plating solution to enhance the morphology of electroplated copper. In this study, the nucleation and growth behavior of copper with variation of additives are studied. The leveling characteristics are analyzed on artificially fabricated Ni bumps.

• Journal of the Korean Wood Science and Technology
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• v.44 no.5
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• pp.750-759
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• 2016

The $MnO_2$ electrodeposited on the surface of the carbon nanofiber mats ($MnO_2$-LCNFM) were prepared from electrospun lignin-g-PAN copolymer via heat treatments and subsequent $MnO_2$ electrodeposition method. The resulting $MnO_2$-LCNFM was evaluateed for its potential use in a supercapicitor electrode. The increase of $MnO_2$ electric deposition time was revealed to increase diameter of carbon nanofibers as well as $MnO_2$ content on the surface of carbon nanofiber mats as confirmed by scanning electon microscope (SEM) analysis. The electrochemical properties of $MnO_2$-LCNFM electrodes are evaluated through cyclic voltammetry test. It was shown that $MnO_2$-LCNFM electrode exhibited good electrochemical performance with specific capacitance of $168.0mF{\cdot}cm^{-2}$. The $MnO_2$-LCNFM supercapacitor successfully fabricated using the gel electrolyte ($H_3PO_4$/Polyvinyl alcohol) showed to have the capacitance efficiency of ~90%, and stable behavior during 1,000 charging/discharging cycles.

• Journal of Energy Engineering
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• v.5 no.2
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• pp.108-114
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• 1996

It is one of the most important factors to enhance the efficiency of the solar collectors by in-creasing collecting efficiency and decreasing heat loss. The pulse electrodeposition method has been involved in this study to improve characteristics of the solar selective coating on 230cm${\times}$60cm substrates and electrical efficiency of the process. The composition of the electrolyte was 280 g/$\ell$ chromic acid, 15 g/$\ell$ propionic acid, and 10 g/$\ell$ appropriate additive. 230cm${\times}$60cm copper and aluminium sheets were utilized as the substrates. It has been observed that the black chrome coatings exhibited reasonable optical properties for commercialization when the plating parameters were properly controlled; the absorptance was 0.98 and 0.97 and omittance was 0.17 and 0.23 for copper and aluminium substrate, respectively. This study implies that the pulse current electrolysis method could be applied to the large scale substrates, and the various products can be avilable after the consideration of the thermal conductivity, heat transfer efficiency and cost problems of the substrates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.49-49
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• 2009

최근 범세계적인 그린에너지 정책에 관련해 화석연료를 대체할 수 있는 수소, 풍력, 태양광 등의 대체 에너지에 대한 관심이 고조되고 있다. 이러한 여러 대체에너지 중에서도 태양광을 전기에너지로 변환하는 태양전지에 관한 연구가 집중되고 있다. 태양전지는 구조적으로 단순하고 제조 공정도 비교적 간단하지만, 보다 널리 보급되기 위해서는 경제성 향상이라는 문제점을 해결해야 한다. 이를 위해서는 기존의 실리콘 태양전지를 대체할 수 있는 신물질에 대한 연구가 필요하며, 그 중에서도 반도체 기술을 이용한 박막형 태양전지는 기존의 실리콘 태양 전지가 가지고 있는 고비용이라는 문제점을 극복할 수 있을 것으로 기대를 모으고 있다. 박막형 태양전지의 박막 재료로는 CIGS, CdTe 등이 연구되어지고 있지만, 아직까지는 기존의 실리콘 태양전지에 비해 에너지변환효율이 낮은 이유로 인해 실용화가 많이 이루어지지 못하고 있는 것이 사실이다. 이러한 박막형 태양전지의 재료들 중에서도 CdTe는 이종접합 박막형 태양전지에 흡광층으로 사용되는 것으로 상온에서 1.45eV 정도의 밴드갭(band gap) 에너지를 갖는 II-VI족 화합물반도체로써 태양광 스펙트럼과 잘 맞는 이상적인 밴드랩 에너지와 높은 광흡수도 때문에 박막형 태양전지로 가장 주목을 받고 있다. CdTe 박막의 제조 방법으로는 진공증착법(vacuum evaporation), 전착법(electrodeposition), 스퍼터링법(sputtering) 등이 있지만 본 연구에서는 스퍼터링법을 이용하여 박막을 증착하였다. 이상과 같이 증착된 CdTe 박막을 화학적기계적연마(CMP, chemical mechanical polishing) 공정을 적용시킴으로써, 태양전지의 에너지변환효율에 직접적인 영향을 끼칠 수 있는 CdTe 박막의 물리적, 전기적 특성들의 변화를 연구하기 위한 선행 연구를 진행하였다. 특히 본 연구에서는 CdTe 박막의 화학적 기계적 연마 특성을 분석하여 정규화를 통한 모델링을 수행하였다. 또한 화학적기계적연마 공정 전과 후의 표면 특성을 관찰하기 위해 SEM(scanning electron microscopy)과 AFM(atomic forced microscope)를 이용하였으며, 구조적 특성 관찰을 XRD(X-ray diffraction)를 사용하여 실험을 수행하였다.

• Korean Journal of Materials Research
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• v.20 no.12
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• pp.661-668
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• 2010

Cu(In,Ga)$Se_2$(CIGS) photovoltaic thin films were electrodeposited on Mo/glass substrates with an aqueous solution containing 2 mM $CuCl_2$, 8 mM $InCl_3$, 20 mM $GaCl_3$ and 8mM $H_2SeO_3$ at the electrodeposition potential of -0.6 to -1.0 V(SCE) and pH of 1.8. The best chemical composition of $Cu_{1.05}In_{0.8}Ga_{0.13}Se_2$ was found to be achieved at -0.7 V(SCE). The precursor Cu-In-Ga-Se films were annealed for crystallization to chalcopyrite structure at temperatures of 100-$500^{\circ}C$ under Ar gas atmosphere. The chemical compositions, microstructures, surface morphologies, and crystallographic structures of the annealed films were analyzed by EPMA, FE-SEM, AFM, and XRD, respectively. The precursor Cu-In-Ga-Se grains were grown sparsely on the Mo-back contact and also had very rough surfaces. However, after annealing treatment beginning at $200^{\circ}C$, the empty spaces between grains were removed and the grains showed well developed columnar shapes with smooth surfaces. The precursor Cu-In-Ga-Se films were also annealed at the temperature of $500^{\circ}C$ for 60 min under Se gas atmosphere to suppress the Se volatilization. The Se amount on the CIGS film after selenization annealing increased above the Se amount of the electrodeposited state and the $MoSe_2$ phase occurred, resulting from the diffusion of Se through the CIGS film and interaction with Mo back electrode. However, the selenization-annealed films showed higher crystallinity values than did the films annealed under Ar atmosphere with a chemical composition closer to that of the electrodeposited state.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.67-74
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• 2018

Thermoelectric thin film modules were fabricated by electroplating p-type $Sb_2Te_3$and n-type $Bi_2Te_3$ thin film legs with the same thickness of $20{\mu}m$ and different diameters of $100{\mu}m$, $300{\mu}m$, and $500{\mu}m$, respectively. The output voltage and output power of thin film modules were measured and compared as a function of the leg diameter. The modules processed with thin film legs of $100{\mu}m$, $300{\mu}m$, and $500{\mu}m$-diameter exhibited open circuit voltages of 365 mV at ${\Delta}T=36.7K$, 142 mV at ${\Delta}T=37.5K$, and 53 mV at ${\Delta}T=36.1K$, respectively. Maximum output powers of $845{\mu}W$ at ${\Delta}T=36.7K$, $631{\mu}W$ at ${\Delta}T=37.5K$, and $276{\mu}W$ at ${\Delta}T=36.1K$ were obtained for the modules fabricated with the thin film legs of $100{\mu}m$, $300{\mu}m$, and $500{\mu}m$-diameter, respectively.