• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.54-55
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• 2002

최근 자성박막과 이를 이용해 전자의 스핀을 제어할 수 있게 되면서, 이를 이용한 자기미세소자에 대해 많은 연구가 이루어지고 있다. 그 중 자성 다층박막과 자성 터널 접합에 대한 연구가 많이 행해지고 있는데, Co/cu 다층박막으로 제조한 소자는 상온에서도 65%를 넘는 큰 자기저항비를 보여주고 있다[1]. 또 다른 자기전자소자로 스핀 밸브 트랜지스터(SVT)가 있다[2]. 스핀 밸브 트랜지스터는 두 반도체 기판 사이에 금속 박막을 다층으로 삽입된 구조로 구성되어있다. (중략)

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.45-46
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• 2015

Se 원소가 포함된 $CuIn_xGa_{1-x}Se_2$(CIGS) 단일 스퍼터링 타겟을 이용하여 후처리 공정없이 단일 스퍼터링 공정만으로 CIGS 흡수층 박막을 증착하여 소자 특성을 확인하였다. 단일 CIGS 흡수층 공정이 적용된 CIGS 박막태양전지 소자(유리기판/Mo/단일 CIGS 흡수층 박막/CdS/i-ZnO/Al-doped ZnO/Ni-Al grid)에서 10.0%의 태양광 변환 효을을 달성하였으며, 이는 기존의 복잡한 공정구조를 해결하여 대면적 양산화 CIGS 제조 공정에도 적용할 수 있음을 확인하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.393-393
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• 2016

Cu(In,Ga)Se2 (CIGS) 박막 태양전지는 높은 효율과 낮은 제조비용, 높은 신뢰성으로 인해 박막 태양전지 중 가장 각광받고 있다. 특히 유리기판 대신 가볍고 유연한 철강소재나 플라스틱 소재를 이용하여 발전분야 외에 건물일체형, 수송용, 휴대용등 다양한 분야에 적용이 가능하다. 이러한 유연 기판을 이용한 CIGS 태양전지의 개발을 위해서는 기판의 특성에 따른 다양한 공정개발이 선행되어야 한다. Stainless steel과 같은 철강기판의 경우 Fe, Ni, Cr등의 불순물이 확산되어 흡수층의 특성을 저하시켜 효율을 감소시킨다. 따라서 이러한 철강 기판의 경우 불순물의 확산을 방지하는 확산방지막이 필수적이다. 이러한 유연기판의 특성을 고려하여 본 연구에서는 기존의 두껍고 추가 장비가 요구되는 SiOx나 Al2O3 대신 200nm 이하의 ZnO 박막을 이용하여 확산방지막을 제조하였다. 유연기판으로 STS 430 stainless steel을 이용하였다. 먼저 stainless steel 기판을 이용하여 기판에 의한 흡수층의 특성을 분석하였으며 ZnO 확산 방지막의 유무 및 두께에 따른 흡수층 및 소자의 특성을 분석하였다. 이때 확산 방지막은 기존 TCO 공정에서 사용되는 i-ZnO를 사용하였으며 RF sputter를 이용하여 50~200nm로 두께를 달리하며 특성 비교를 실시하였다. 효율은 확산방지막을 적용하지 않았을 때 약 5.9%에서 확산 방지막 적용시 약 10.7%로 증가하였다. 그 후 기판으로부터 확산되는 불순물의 유입에 의한 결함을 분석하기 위해 DLTS를 이용하여 소자 특성을 분석하였다. 온도는 80~300K으로 가변하며 측정을 실시하였으며 그 후 계산을 통해 activation energy와 capture cross section 값을 구하였다. DLTS 분석 결과 Ni이 CIGS 흡수층으로 확산되어 NiCu anti-site를 형성하여 태양전지의 효율을 감소시키는 것을 확인하였다. 모든 흡수층은 Co-Evaporation 방법을 이용하여 제조하였으며 제조된 흡수층은 SEM, XRF, XRD, GD-OES, PL, Raman등을 이용하여 분석하였으며 그 외 일반적인 방법을 이용하여 Mo, CdS, TCO, Al grid를 제조하였다. AR 코팅은 제외 하였으며 제조된 소자는 솔라 시뮬레이터를 이용하여 효율 특성 분석을 실시하였으며 Q.E. 분석을 실시하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.10
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• pp.625-630
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• 2017

ZnS was chemically deposited as a buffer layer alternative to CdS, for use as a Cd-free buffer layer in $Cu(In_{1-x}Ga_x)Se_2$ (CIGS) solar cells. The deposition of a thin film of ZnS was carried out by chemical bath deposition, following which the structural and optical properties of the ZnS layer were studied. For the experiments, zinc sulfate hepta-hydrate ($ZnSO_4{\cdot}7H_2O$), thiourea ($SC(NH_2)_2$), and ammonia ($NH_4OH$) were used as the reacting agents. The mole concentrations of $ZnSO_4$ and $SC(NH_2)_2$ were fixed at 0.03 M and 0.8 M, respectively, while that of ammonia, which acts as a complexing agent, was varied from 0.3 M to 3.5 M. By varying the mole concentration of ammonia, optimal values for parameters like optical transmission, deposition rate, and surface morphology were determined. For the fixed mole concentrations of $0.03M\;ZnSO_4{\cdot}7H_2O$ and $0.8M\;SC(NH_2)_2$, it was established that 3.0 M of ammonia could provide optimal values of the deposition rate (5.5 nm/min), average optical transmittance (81%), and energy band gap (3.81 eV), rendering the chemically deposited ZnS suitable for use as a Cd-free buffer layer in CIGS solar cells.

• Toxicological Research
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• v.29 no.3
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• pp.211-215
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• 2013

The trace toxic metal copper was assayed using mercury immobilized on a carbon nanotube electrode (MCW), with a graphite counter and a reference electrode. In this study, a macro-scale convection motor was interfaced with a MCW three-electrode system, in which a handmade MCW was optimized using cyclic- and square-wave stripping voltammetry. An analytical electrolyte for tap water was used instead of an expensive acid or base ionic solution. Under these conditions, optimum parameters were 0.09 V amplitude, 40 Hz frequency, 0.01 V incremental potential, and a 60-s accumulation time. A diagnostic working curve was obtained from 50.0 to 350 ${\mu}g/L$. At a constant Cu(II) concentration of 10.0 ${\mu}g/L$, the statistical relative standard deviation was 1.78% (RSD, n = 15), the analytical accumulation time was only 60 s, and the analytical detection limit approached 4.6 ${\mu}g/L$ (signal/noise = 3). The results were applied to non-treated drinking water. The content of the analyzed copper using 9.0 and 4.0 ${\mu}g/L$ standards were 8.68 ${\mu}g/L$ and 3.96 ${\mu}g/L$; statistical values $R^2$ = 0.9987 and $R^2$ = 0.9534, respectively. This method is applicable to biological diagnostics or food surveys.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.877-881
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• 2006

We obtained sputtering yields for the MgO, $MgAl_2O_4$ and $MgAl_2O_4/MgO$ films using the FIB system. $MgAl_2O_4/MgO$ protective layers have been found to have less $24^{\sim}^30%$ sputtering yield values from 0.24 atoms/ion up to 0.36 atoms/ion than MgO layers with the values from 0.36 atoms/ion up to 0.45 atoms/ion for irradiated $Ga^+$ ion beam whose energies ranged from 10 keV to 14 keV. And $MgAl_2O_4$ layers have been found to have lowest sputtering yield values from 0.88 up to 0.11. It is also found that $MgAl_2O_4/MgO$ and MgO have secondary electron emission $coefficient({\gamma})$ values from 0.09 up to 0.12 for $Ne^+$ ion whose energies ranged from 50 eV to 200 eV.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.106.1-106.1
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• 2011

The Cu(In,Ga)Se2 (CIGS) thin film solar cells have been achieved until almost 20% efficiency by NREL. These solar cells include chemically deposited CdS as buffer layer between CIGS absorber layer and ZnO window layer. Although CIGS solar cells with CdS buffer layer show excellent performance, the short wavelength response of CIGS solar cell is limited by narrow CdS band gap of about 2.42 eV. Taking into consideration the environmental aspect, the toxic Cd element should be replaced by a different material. Among Cd-free candidate materials, the CIGS thin film solar cells with ZnS buffer layer seem to be promising with 17.2%(module by showa shell K.K.), 18.6%(small area by NREL). However, ZnS/CIGS solar cells still show lower performance than CdS/CIGS solar cells. There are several reported reasons to reduce the efficiency of ZnS/CIGS solar cells. Nakada reported ZnS thin film had many defects such as stacking faults, pin-holes, so that crytallinity of ZnS thin film is poor, compared to CdS thin film. Additionally, it was known that the hetero-interface between ZnS and CIGS layer made unfavorable band alignment. The unfavorable band alignment hinders electron transport at the heteo-interface. In this study, we focused on growing defect-free ZnS thin film and for favorable band alignment of ZnS/CIGS, bandgap of ZnS and CIGS, valece band structure of ZnS/CIGS were modified. Finally, we verified the photovoltaic properties of ZnS/CIGS solar cells.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.70-70
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• 2011

The prospects of current and coming solar-photovoltaic (PV) technologies are envisioned, arguing this solar-electricity source is beyond a tipping point in the complex worldwide energy outlook. Truly, a revolution in both the technological advancements of solar PV and the deployment of this energy technology is underway; PV is no longer an outlier. The birth of modern photovoltaics (PV) traces only to the mid-1950s, with the Bell Telephone Laboratories' development of an efficient, single-crystal Si solar cell. Since then, Si has dominated the technology and the markets, from space through terrestrial applications. Recently, some significant shift toward technology diversity have taken place. Some focus of this presentation will be directed toward PV R&D and technology advances, with indications of the limitations and relative strengths of crystalline (Si and GaAs) and thin-film (a-Si:H, Si, Cu(In,Ga)(Se,S)2, CdTe). Recent advances, contributions, industry growth, and technological pathways for transformational now and near-term technologies (Si and primarily thin films) and status and forecasts for next-generation PV (nanotechnologies and non-conventional and "new-physics" approaches) are evaluated. The need for R&D accelerating the now and imminent (evolutionary) technologies balanced with work in mid-term (disruptive) approaches is highlighted. Moreover, technology progress and ownership for next generation solar PV mandates a balanced investment in research on longer-term (the revolution needs revolutionary approaches to sustain itself) technologies (quantum dots, multi-multijunctions, intermediate-band concepts, nanotubes, bio-inspired, thermophotonics, ${\ldots}$ and solar hydrogen) having high-risk, but extremely high performance and cost returns for our next generations of energy consumers. This presentation provides insights to the reasons for PV technology emergence, how these technologies have to be developed (an appreciation of the history of solar PV)-and where we can expect to be by this mid-21st century.

• Journal of the Korean Vacuum Society
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• v.15 no.4
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• pp.395-403
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• 2006

It is known that $MgAl_2O_4$ has higher resistance to moisture than MgO, in humid ambient MgO is chemically unstable. It reacts very easily with moisture in the air. In this study, the characteristic of $MgAl_2O_4$ and $MgAl_2O_4/MgO$ layers as dielectric protection layers for AC- PDP (Plasma Display Panel) have been investigated and analysed in comparison for conventional MgO layers. MgO and $MgAl_2O_4$ films both with a thickness of $1000\AA$ and $MgAl_2O_4/MgO$ film with a thickness of $200/800\AA$ were grown on the Cu substrates using the electron beam evaporation. $1000\AA$ thick aluminium layers were deposited on the protective layers in order to avoid the charging effect of $Ga^+$ ion beam while the focused ion beam(FIB) is being used. We obtained sputtering yieds for the MgO, $MgAl_2O_4$ and $MgAl_2O_4/MgO$ films using the FIB system. $MgAl_2O_4/MgO$ protective layers have been found th show $24{\sim}30%$ lower sputtering yield values from 0.244 up to 0.357 than MgO layers with the values from 0.364 up to 0.449 for irradiated $Ga^+$ ion beam with energies ranged from 10 kV to 14 kV. And $MgAl_2O_4$ layers have been found to show lowest sputtering yield values from 0.88 up to 0.109. Secondary electron emission coefficient(g) using the ${\gamma}$- FIB. $MgAl_2O_4/MgO$ and MgO have been found to have similar g values from 0.09 up to 0.12 for indicated $Ne^+$ ion with energies ranged from 50 V to 200 V. Observed images for the surfaces of MgO and $MgAl_2O_4/MgO$ protective layers, after discharge degradation process for 72 hours by SEM and AFM. It is found that $MgAl_2O_4/MgO$ protective layer has superior hardness and degradation resistance properties to MgO protective layer.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.52-57
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• 2004

In this research, characteristics of air core rectangular spiral type inductors of ㎓ band are numerical analyzed. The basic structure of inductors is a rectangular spiral having 390${\mu}{\textrm}{m}$${\times}$390${\mu}{\textrm}{m}$ size, 5.5 turns, line width of 10 ${\mu}{\textrm}{m}$ and line space of 10 ${\mu}{\textrm}{m}$. Frequency characteristics were simulated up to 10 ㎓. The substrate was modeled as Si, Sapphire, glass and GaAs and the conductor as Cu. The thickness of the conductor was fixed at 2. The number of turns was n.5 to make the input and output terminals to be on the opposite sides. The initial inductance of the basic inductor structure was 13.0 nH, maximum inductance 60.0 nH and resonance frequency 4.25 ㎓. As the dielectric constant of the substrate was increased, the initial inductance varied only slightly, but the resonance frequency decreased considerably. As the number of turns was varied from 1.5 to 9.5, the initial inductance was increased linearly from 2.9 nH to 15.9 nH and, then, saturated at 16.9 nH. The Q factor increased only slightly. The line width and line space of inductors were varied from 5 ${\mu}{\textrm}{m}$ to 20 ${\mu}{\textrm}{m}$, which resulted in the decrease of the initial and maximum inductances. But the resonance frequency was increased. Q factor displayed an increase and a decrease, respectively, when the line width and line space were increased.