• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.237.1-237.1
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• 2015

OLED의 낮은 외부 광자 효율 문제를 해결하기 위해서는 발광층은 물론 전극 재료에 대한 연구가 함께 진행되어야 한다. 최근 플렉서블 디스플레이(Flexible Display) 분야에서 투명전극(Transparent Electrode)은 큰 주목을 받고 있다. 기존 전자소자의 투명전극으로는 인듐산화물(ITO, Indium Tin Oxide)이 널리 사용되어 왔으나, ITO의 주원료인 인듐(Indium)은 희소성으로 인해 앞으로 30년 후에 고갈될 것으로 예상되어 ITO를 대체할만한 투명전극 재료가 필요하게 되었다. 인듐이 포함되지 않은(Indium-free) 투명전극을 개발하려는 많은 연구들이 진행 중인데, 본 연구에서는 PEN(Polyethylene Naphthalate) 유연기판 상에 그래핀(Graphene)을 투명전극으로 구현하여 OLED의 효율을 높이는데 이용하고자 하였다. 화학 기상 증착(CVD, Chemical Vapor Deposition) 방법을 이용하여 Cu 호일 위에 그래핀을 성장시킨 후 PEN 유연기판에 전사하여 그래핀 투명전극을 구현하면서 그래핀 성장층을 단층 또는 다층으로 구분하여 성장시켜 각각의 투명전극을 구현해보았다. 유연기판 상의 그래핀의 상태를 확인하기 위해 라만 분광(Raman Spectroscopy) 분석을 이용하여 그래핀 고유의 라만 꼭지점(Raman peak)인 G 꼭지점(G peak: 1580 cm-1), 2D 꼭지점(2D peak: ~2700 cm-1)을 확인하였는데 그래핀 전사 상태가 양호하여 D 꼭지점(D peak: ~1360 cm-1)은 나타나지 않았다. 원자힘 현미경(AFM, Atomic Force Microscope) 분석을 통해 다층 및 단층 그래핀 표면의 거칠기(Roughness) 및 두께(Thickness)를 각각 확인할 수 있었고 자외선-가시광선 분광법(UV-Visible Spectroscopy) 분석으로 그래핀 투명전극과 유연기판의 투과도(Transmittance)를 분석하였으며, 단층 그래핀 투과도가 90%수준의 높은 값이 나타나 ITO보다 개선됨을 확인하였다. 그래핀 면저항은 TLM(Transmission Line Measurement)법을 통해 측정하였는데, 단층 그래핀의 경우 $800{\Omega}/{\square}$ 내외 수준임을 확인할 수 있었다. 본 연구에서는 근자외선 영역에서 높은 투과도와 우수한 전기적 특성을 가지는 그래핀 투명 전도성 전극 구조를 제안하고, 나아가 가시영역에서 ITO를 대체할 수 있는 투명 전도성 전극 물질을 개발함으로써 발광다이오드의 광효율을 높일 수 있는 투명 전도성 전극을 구현하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3054-3059
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• 2009

Natural black diamonds of single crystal, polycrystalline, and agglomerated roughs become important for their industrial and gem stone application. We performed the conventional gemological tests of thermal diffusion, apparent density, scratch test, and magnification test as well as the advanced tests of Raman spectroscopy, X-ray diffraction test and Lang topography. We conclude that scratch test with SiC paper was the most efficient method in view point of speed and cost. Raman spectroscopy and XRD were useful for identification of diamond while Lang topography offered a good visualization method of the grain structure of polycrystalline black diamond roughs.

• The Korea Journal of Herbology
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• v.35 no.4
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• pp.1-8
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• 2020

Objectives : Angelicae gigas, A. sinensis and A. acutiloba are three types of plants used as Angelicae Radix (Dang-Gui). Many doctors of Korean medicine want to know the difference in clinical use of these three species. This study aimed to compare the hemoglobin-related activity of the extracts of Angelicae gigas, A. sinensis and A. acutiloba roots by measuring the intensity of binding oxygen to hemoglobin using Raman spectroscopy. Methods : Hemoglobin activity was measured by chemical analysis and Raman spectroscopy to compare the pharmaceutical efficacy of three Angelica root extracts. The oxygenated hemoglobin intensity, blood decursinol and acetylcholinestrase(AChE) concentration in mice were measured. In addition, the effects of three Angelica root extracts on oxygenated hemoglobin intensity, decursinol and AChE concentration in red blood cells (RBC) from human were also investigated. Results : The contents of decursin, decursinol and decursinol angelate, which affected physiological activity and RBC properties, were higher in the extract of A. gigas root than in those of A. sinensis and A. acutiloba roots. Moreover, oxygenated hemoglobin intensity in the A. gigas extract was higher than that of other two species in the blood of mice and human RBCs. Also, the blood decursinol and AChE concentrations of A. gigas root extract were higher than that of A. sinensis and A. acutiloba roots. Conclusions : These results suggest that A. gigas is more effective in treating disease related oxygen deficiency in RBC deformation under oxidative stress.

• Bulletin of the Korean Chemical Society
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• v.19 no.1
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• pp.5-21
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• 1998

The purpose of this paper is to show that X-ray absorption spectroscopy (XANES and EXAFS) is a powerful technique for characterizing both crystalline and amorphous solids from structural (local order) and electronic point of view. The principle of this technique is briefly described by showing the main factors which must be considered for recording and fitting the experimental results. Some non-trivial examples have been selected for demonstrating that XAS spectroscopy is the only technique for bringing a definitive answer as for example: the determination of the local distortion of the $NiO_6$ octahedra in the $Li_{1-z}Ni_{1+z}O_2$ layered oxides and the evidence of the presence of copper pairs in the NASICON-type phosphate $CuZr_2 (PO_4)_3$. Are also reported some significant examples for which XAS spectroscopy is decisive with other characterization methods as (i) Raman spectroscopy for glasses (ii) Mossbauer spectroscopy for $LiNi_{1+z-t}Fe_To_2$ oxides (iii) magnetic measurements for Ce-based intermetallic compounds.

• Journal of the Korean Vacuum Society
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• v.17 no.2
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• pp.170-174
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• 2008

We have studied, using Raman and photoluminescence (PL) spectroscopy, material property changes of single-walled carbon nanotubes (SWCNTs) dispersed in sodium dodecyl sulfate(SDS) aqueous solution by ultrasonication. Radial breathing mode Raman intensities of the dispersed SWCNTs shows different behavior depending on their chiralities as the sonication time increases. As the amount of SWCNTs dispersed in 1wt% SDS solution increases, both a downshift of the G-band Raman frequency and an enhancement in the PL intensity were observed.

• Bulletin of the Korean Chemical Society
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• v.28 no.2
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• pp.193-199
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• 2007

Raman and fluorescence spectroscopies were employed to study the coil effects on the intermolecular structure of a rod-coil liquid crystalline (LC) oligomer, the esterification products of ethyl 4-[4'-oxy-4-biphenylcarbonyloxy]- 4'-biphenylcarboxylate with poly(propylene)oxides (PPO) (DP=12) and poly(ethylene oxide)s (PEO) (DP=12). Three different vibrational modes (carbonyl, aromatic C-H, and aromatic C=C) obtained from the Raman experiment at variable temperature indicate that PPO and PEO coils induce the hydrogen bonding in a different manner. Further information about the micro-environment around the mesogenic unit obtained by fluorescence excitation spectra of P12-4 (LC with PPO coil) and 12-4 (LC with PEO coil) suggests that the mesogenic unit of P12-4 is quite different from that of 12-4 in intermolecular structure. This study supports the results obtained only from Raman spectroscopy, providing more accurate information about the intermolecular structural changes of liquid crystalline polymers at a molecular level during the phase transitions.

• Korean Journal of Heritage: History & Science
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• v.56 no.4
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• pp.216-228
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• 2023

The purpose of this study is to apply the handheld Raman spectrometer to identify the coloring materials used in a large Buddhist painting (of Maitreya Buddha) at Janggoksa Temple through cross-validation with HH-XRF. An in situ investigation was performed together with use of a digital microscope and HH-XRF analysis to verify the properties of pigments used in the gwaebul ("large Buddhist painting") via a non-destructive method. However, the identification of coloring materials composed of light elements and mixed or overlaid pigments is difficult using only non-destructive analysis data. Unlike in situ investigation, laboratory analysis often required samples yet the sampling is restricted to a small quantity due to the cultural heritage characteristic. Thus, it is necessary to develop a non-destructive in situ method to supplement the HH-XRF data. The large Buddhist painting at Janggoksa Temple was painted mainly using white, red, yellow, green, and blue colors. The Raman spectroscopy provides molecular information, while XRF spectroscopy provides information about elemental composition of the pigments. Analysis results identified various coloring materials: inorganic pigment, such as lead white, minium, cinnabar, and orpiment, as well as organic pigment such as gamboge and indigo. Therefore, it is possible to obtain more information for the identification of pigments; organic pigment and mixed or overlaid pigments, while at the same time minimizing the collection sample and simplifying the analysis procedure compared to previously used methods. The results of this study will be used as basic data for the analysis of painting cultural heritage through a non-destructive in situ method in the future.

• Journal of Sensor Science and Technology
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• v.29 no.4
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• pp.255-260
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• 2020

In this study, we developed a method of improving the surface-enhanced Raman spectroscopy (SERS) response characteristics by depositing a nanoporous Ag metal thin film through cluster source sputtering after forming a pyramidal texture structure on the Si substrate surface. A reactive ion etching (RIE) system with a metal mesh inside the system was used to form a pyramidal texture structure on the Si surface without following a complicated photolithography process, unlike in case of the conventional RIE system. The size of the texture structure increased with the RIE process time. However, after a process time of 60 min, the size of the structure did not increase but tended to saturate. When the RF power increased from 200 to 250 W, the size of the pyramidal texture structure increased from 0.45 to 0.8 ㎛. The SERS response characteristics were measured by depositing approximately 1.5 ㎛ of nanoporous Ag metal thin film through cluster sputtering on the formed texture structure by varying the RIE process conditions. The Raman signal strength of the nanoporous Ag metal thin film deposited on the Si substrate with the texture structure was higher than that deposited on the general silicon substrate by up to 19%. The Raman response characteristics were influenced by the pyramid size and the number of pyramids per unit area but appeared to be influenced more by the number of pyramids per unit area. Therefore, further studies are required in this regard.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.203-203
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• 2014

Due to the electrical properties such as narrow bandgap and high carrier mobility, indium antimonide (InSb) has attracted a lot of attention recently. For the fabrication of electronic or photonic devices, an etching process is required. However, during etching process, enegetic ions can induce structural damages on the bombarded surface. Especially, InSb has a very weak binding energy between In atom and Sb stom, it can be easily damaged by impingement of ions. In the previous work, to evaluate the surface properties after Ar ion beam etching, the plasma-induced structural damage on the etched InSb(100) surface had been examined by resonant Raman spectroscopy. As a result, we demonstrated the relation between the enhanced transverse optical(TO) peak in the Raman spectrum and the ion-induced structral damage near the InSb surface. In this work, the annealing effect on the etched InSb(100) surface has investigated. Annealing process was performed at $450^{\circ}C$ for 10 minute under antimony ambient. As-etched InSb(100) surface had shown a strongly enhanced TO scattering intensity in the Raman spectrum. However, the annealing process with antimony flowing caused the intensity to recover due to the structural reordering and the reduction of antimony vacancies. It proves that the origin of enhanced TO scattering is Sb vacancies. Furthermore, it shows that etching-induced damage can be cured effectively by the following annealing process under Sb ambient.

• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.9-12
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• 2019

We performed Raman spectroscopy on two different over-doped Bi₂Sr₂CaCu₂O_8+x (BSCCO), of which superconducting transition temperatures are 89 K and 77 K. Line-shape analysis of the Raman-spectrum was done, focused on B_1g bond buckling mode which have drawn a lot of attention, since photoemission studies showed an evidence for strong coupling between the mode and electron. The line-shapes show asymmetry and are well fitted by the Fano line-shape formula. Remarkably, we found that the peak line-widths from B_1g bond buckling mode in BSCCO show much broader than those in YBa₂Cu₃O_7-x. The broad line width can be attributed to the superstructure modulation of BSCCO. Our results imply that B_1g bond buckling mode may have close relation to the origin of superconductivity or to boosting the superconducting transition temperature in BSCCO.