• Korean Journal of Materials Research
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• v.23 no.3
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• pp.155-160
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• 2013

ZnO thin films co-doped with Mg and Ga (MxGyZzO, x + y + z = 1, x = 0.05, y = 0.02 and z = 0.93) were prepared on glass substrates by RF magnetron sputtering with different sputtering powers ranging from 100W to 200W at a substrate temperature of $350^{\circ}C$. The effects of the sputtering power on the structural, morphological, electrical, and optical properties of MGZO thin films were investigated. The X-ray diffraction patterns showed that all the MGZO thin films were grown as a hexagonal wurtzite phase with the preferred orientation on the c-axis without secondary phases such as MgO, $Ga_2O_3$, or $ZnGa_2O_4$. The intensity of the diffraction peak from the (0002) plane of the MGZO thin films was enhanced as the sputtering power increased. The (0002) peak positions of the MGZO thin films was shifted toward, a high diffraction angle as the sputtering power increased. Cross-sectional field emission scanning electron microscopy images of the MGZO thin films showed that all of these films had a columnar structure and their thickness increased with an increase in the sputtering power. MGZO thin film deposited at the sputtering power of 200W showed the best electrical characteristics in terms of the carrier concentration ($4.71{\times}10^{20}cm^{-3}$), charge carrier mobility ($10.2cm^2V^{-1}s^{-1}$) and a minimum resistivity ($1.3{\times}10^{-3}{\Omega}cm$). A UV-visible spectroscopy assessment showed that the MGZO thin films had high transmittance of more than 80 % in the visible region and that the absorption edges of MGZO thin films were very sharp and shifted toward the higher wavelength side, from 270 nm to 340 nm, with an increase in the sputtering power. The band-gap energy of MGZO thin films was widened from 3.74 eV to 3.92 eV with the change in the sputtering power.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.39 no.1 s.119
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• pp.38-47
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• 2007

This study was carried out to develop a new application field and obtain the basic data of citrus peel as waste in Jeju island and traditional Hanji for producing functional Hanji. The results measuring physical and optical properties, water vapor permeance and antibacterial activity are as follows. It was revealed that apparent density go as down but bulk raise up in the structural view of Hanji with increasing of the addition various Korean citrus peel (citrus unshiu, cheonggyun and hanrabong peel, and citrus unshiu peel powder) percentages, and that the density of Hanji added citrus unshiu peel was higher, but bulk was lower in compared with Hanji added other kinds of peel. Those Hanji added citrus unshiu peel, cheonggyun peel, hanrabong peel and citrus unshiu powder were very great not only in the strength (breaking length, burst index, tear index and folding endurance) but also in water vapor permeant rate in comparison with Hanji. The pHs of Hanji were neutrality (7 to 8). The brightness of the Hanji added various citrus peel percentages was low in compared to Hanji, and the 40% addition of hanrabong peel was the lowest. When 40% hanrabong peel was added to Hanji, it was very yellow in the color degree. When cheonggyun peel was added to Hanji manufacture, water vapor permeant rate was highly effective. It is known that vacant space of intrafiber was reduced by image analysis of Hanji and the additions of peel of citrus unshiu, cheonggyun and hanrabong were distributed equally in the interior of Hanji. The antibacterial activity of Hanji added citrus unshiu peel is more than 98%. After all, it would be able to increase utilization of Hanji, extensively. Namely, production of high quality Hanji added functional materials is expected for new valuable industry of citrus peel and Hanji.

• Journal of the Korean Wood Science and Technology
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• v.46 no.3
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• pp.231-240
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• 2018

Bamboo is one of the major biomass resources that have many advantages such as fast growing, easy cultivation, short rotation, and a relatively lower price. In this study, the anatomical characteristics of Moso bamboo (Phyllostachys pubescens) by age from one-year-old to five-year-old were examined by optical and scanning electron microscopy. Also, the crystalline properties such as relative crystallinity and crystallite width were investigated by an X-ray diffraction method. In one-year-old bamboo xylem, a few vascular bundles showed missing bundle sheath in near the intercellular space. Moreover, one-year-old bamboo had the shortest fiber length and the smallest values in vessel diameter, width of vascular bundle, and thickness of inner layer. One-year-old bamboo also showed the smallest values in the crystallinity and crystallite width. Near epidermis samples had longer fiber length and greater vascular bundle spacing than near pith samples. Relative crystallinity and crystallite width near the epidermis were also higher than near the pith. This study revealed significant differences in qualitative and quantitative anatomical characteristics between one-year-old and two-year- or more old Moso bamboos. It is concluded that the structural differences by bamboo age can be used to differentiate the characteristics of juvenile and mature bamboo.

• Korean Journal of Materials Research
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• v.27 no.11
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• pp.631-635
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• 2017

We report facile solution processing of mesoporous hematite (${\alpha}-Fe_2O_3$) thin films for high efficiency solar-driven water splitting. $Fe_2O_3$ thin films were prepared on fluorine doped tin oxide(FTO) conducting substrates by spin coating of a precursor solution followed by annealing at $550^{\circ}C$ for 30 min. in air ambient. Specifically, the precursor solution was prepared by dissolving non-toxic $FeCl_3$ as an Fe source in highly versatile dimethyl sulfoxide(DMSO) as a solvent. The as-deposited and annealed thin films were characterized for their morphological, structural and optical properties using field-emission scanning electron microscopy(FE-SEM), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and UV-Vis absorption spectroscopy. The photoelectrochemical performance of the precursor (${\alpha}-FeOOH$) and annealed (${\alpha}-Fe_2O_3$) films were characterized and it was found that the ${\alpha}-Fe_2O_3$ film exhibited an increased photocurrent density of ${\sim}0.78mA/cm^2$ at 1.23 V vs. RHE, which is about 3.4 times higher than that of the ${\alpha}-FeOOH$ films ($0.23mA/cm^2$ at 1.23 V vs. RHE). The improved performance can be attributed to the improved crystallinity and porosity of ${\alpha}-Fe_2O_3$ thin films after annealing treatment at higher temperatures. Detailed electrical characterization was further carried out to elucidate the enhanced PEC performance of ${\alpha}-Fe_2O_3$ thin films.

• Journal of the Korean Applied Science and Technology
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• v.34 no.2
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• pp.260-270
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• 2017

Zirconia has white color and physical, chemical stability, also using in high temperature materials and various industrial structural ceramics such as heat insulating materials and refractories due to their low thermal conductivity, excellent strength, toughness, and corrosion resistance. If hydrophobically modified zirconia is introduced into a hydrophobic acrylate coating solution, the hardness, chemical, electrical, and optical properties will be improved due to the better dispersibility of inorganic particle in organic coating media. Thus, we introduced $-CH_3$ group through silylation reaction using either trimethylchlorosilane(TMCS) or hexamethyldisilazane(HMDZ) on zirconia surface. The $Si-CH_3$ peaks derived from TMCS and HMDZ on hydrophobically modified zirconia surface was confirmed by FT-IR ATR spectroscopy, and introduction of silicon was confirmed by FE-SEM/EDS and ICP-AES. In addition, the sedimentation rate result in acrylate monomer of the modified zirconia showed the improved dispersibility. Comparison of the sizes of a pristine and the modified zirconia particles, which were clearly measured not by the normal microscope but by particle size analysis, provided a pulverizing was occurred by physical force during the silylation process. From the BET analysis data, the specific surface area of zirconia was approximately $18m^2/g$ and did not significantly change during modification process.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.4
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• pp.140-144
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• 2014

Co-(0.7 wt%) and Pr-(2.0, 3.5 or 5.0 wt%) doped cubic zirconia ($ZrO_2:Y_2O_3=50:50wt%$) single crystals grown by a skull melting method were heat-treated in $N_2$ at $1150^{\circ}C$ for 5 hrs. The brown colored as-grown single crystals were changed into either dark brownish green, greenish blue and light green color after the heat treatment. Before and after the heat treatment, the YSZ (yttria-stabilized zirconia) single crystals were cut for wafer form (${\phi}7.5mm{\times}t3mm$). The optical and structural properties were examined by UV-VIS spectrophotometer and X-ray diffraction. Absorption by $Co^{2+}$(${\fallingdotseq}589nm$: ${\Gamma}_8[^4A_2(^4F)]{\rightarrow}{\Gamma}_8+{\Gamma}_7[^4T_1(^4F)]$, ${\fallingdotseq}610nm$: ${\Gamma}_8[^4A_2(^4F)]{\rightarrow}{\Gamma}_8[^4T_1(^4F)]$], ${\fallingdotseq}661nm$: ${\Gamma}_8[^4A_2(^4F)]{\rightarrow}{\Gamma}_6[^4T_1(^4F)]$]) and $Pr^{3+}$(${\fallingdotseq}450nm$: ${^3}H{_4}-{^3}P{_2}$, ${\fallingdotseq}473nm$: ${^3}H{_4}{\rightarrow}{^3}P{_1}$, ${\fallingdotseq}484nm$: ${^3}H{_4}{\rightarrow}{^3}P{_0}$), change of ionization energy and lattice parameter were confirmed.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.1
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• pp.1-10
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• 1999

InGaP epilayers were grown on the flat, $2^{\circ}$off, $6^{\circ}$ off, and $10^{\circ}$off GaAs substrates by organo-metallic vapor phase epitaxy, and influences of crystallographic misorientation of the substrate on the structural and optical properties such as lattice mismatch, elastic strain, lattice curvature, misfit stress, and PL intensity /line-width were investigated in this study. Material characterizations were carried out by TXRD( tripple-axis x-ray diffractometer) and low temperature (11K) PL (photoluminescence). With increase of the substrate misorientation angle (S.M.A.), the relative incorporation of Ga atoms on the substrate surface was found to be enhanced. Also, with increase of the S. M. A., the x-ray line-width of the InGaP epilayer was reduced, indicating that the crystal quality of the epilayer could be improved tilth a misoriented substrate. It was also found that the elastic accommodation of the strain-free lattice misfit was more remarkable in a misoriented sample. PL intensity increased, and PL line-width and emission wavelength decreased with the increase of S. M. A. The results conclude that the elastic characteristics and the crystal quality of the InGaP epilayer could be remarkably enhanced when the misoriented substrates were employed.

• Applied Chemistry for Engineering
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• v.17 no.6
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• pp.644-647
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• 2006

The indium zinc oxide (IZO) thin films were deposited using a radio frequency reactive magnetron sputtering method. Among the various processing variables, $O_{2}$ concentration and annealing temperature after deposition were selected and the optical, electrical, and structural properties of IZO thin films were investigated. As the $O_{2}$ concentration increased, the deposition rate of IZO thin films decreased, the resistivity increased and the transmittance slightly increased. According to atomic force microscopy analysis, the IZO films deposited at pure Ar showed rough surface and those deposited with $O_{2}$ addition exhibited relatively smooth surface. The IZO thin films deposited at pure Ar were annealed at 250, 350, and $450^{\circ}C$, respectively. The IZO thin film deposited at pure Ar showed the lowest transmittance and resistivity and resistivity greatly increased at the annealing temperature exceeding $250^{\circ}C$. The higher annealing temperature IZO films were annealed at, the smoother surface the films showed. The x-ray diffraction revealed that IZO films annealed at higher temperature had better crystalline structures.

• Journal of Conservation Science
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• v.34 no.2
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• pp.107-118
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• 2018

This report does studied for making the method of conserving bracket murals in Daeungjeon of Jikjisa Temple, through the scientific way. Results of evaluated the conservation status at the braket mural paintings, most serious damage is structural damage like cracks, breakage, and delamination. After optical investigation, a characteristic point wasn't found such as underdrawing or traces of a coat of paint. The ultrasonic examination speed by each wall painting was measured from about 195.8 m/s to 392.7 m/s, according to the location of the surface, and it was able to compare the surface properties according to the location. In Infrared-thermal image measurement shows that wall layer separation and paint layer delamination are closely detected, therefore it was able to judge of damage on the objective way. Material analysis revealed that the walls were made by sand and weathering soil. The wall layer combined sand with less than fine sand size by nearly 5:5, and the finishing layer was found to have mixed medium sand and fine sand at approximately 6:4 rates. However, In case of finishing layer, mixing ratios of sizes less than very fine sand were found to be significantly lower than wall. Therefore, it is estimated that the plysical damage such as the separation between the layers of the walls created in the braket mural paintings, is continuously caused by changes in the internal stresses and volume ratio caused by the density differences between the wall and the finishing layers.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.177-177
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• 2007

ZnO는 3.36eV의 넓은 밴드캡을 가지는 II-IV족 반도체로써 태양전지, LED와 같은 광학적 소자로 이용이 기대가 되는 물질이다. 더욱이, 상온에서의 60meV에 해당하는 큰 엑시톤 에너지와 밴드캡 에지니어링이 가능하다는 장점 때문에 광학적 소자로 널리 이용되고 있는 GaN을 대체할 수 있는 물질로 주목을 받고 있다. 하지만, p-type ZnO는 형성이 어렵고 낮은 이동도와 케리어 농도의 특성을 보이고, 대기 중에 장시간 노출할 경우 n-type ZnO의 특성으로 돌아가는 불안정성을 보이고 있다. 최근에 몇몇의 연구자들에 의해 V족의 원소인 P(phosphorous), N(nitrogen), As(arsenic))를 도핑하여 p-type ZnO의 형성에 대한 논문이 발표되고 있다. 또한, V족 원소 중에 P는 p-type ZnO 형성에 효과적인 도핑 물질로 보고되 고 있다. 본 연구는 마그네트론 스퍼터링을 이용하여 다양한 온도에서 성장된 P도핑 ZnO 박막의 특성에 대해 연구하였다. P도핑된 ZnO 박막은 사파이어 기판에 buffer층을 사용한 Insulator 특성의 ZnO박막위에 400, 500, 600, $700^{\circ}C$에서 성장되 었다. 박막의 특성 분석에는 325nm의 파장을 가지는 He-Cd의 레이져 광원을 사용하여 10K의 저온 PL과 0.5T의 자기장을 사용한 van der Pauw configuration에 의한 Hall effect측정, 그리고 결정성 분석에는 XRD와 TEM을 이용하였다. 상온 Hall-effect 측정 결과, $400{\sim}600^{\circ}C$ 에서 성장된 박막은 n-type의 특성을 보였고, $700^{\circ}C$에서 성장된 Phosphorous 도핑 ZnO박막은 $1.19{\times}10^{17}$의 캐리어 농도를 가지는 p-type의 특성을 보였다. 그리고 XRD분석과 TEM분석을 통하여 박막의 성장온도가 증가 할수록 P도핑된 ZnO박막의 결정성이 향상되는 것을 알 수 있었다. 또한 10K의 저온 PL분석을 통해 p도핑에 의한 액셉터에 관련된 피크들을 관찰할 수 있었다.