• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.12
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• pp.965-971
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• 2001

$\beta$-Ga$_2$O$_3$ nanobelts and nanoparticles were synthesized from mechanically ground GaN powders with thermal annealing in a nitrogen atmosphere and an oxygen atmosphere, respectively. The study of field emission scanning electron microscopy (FESEM) on the microstructures of nanomaterials revealed that the nanobelts synthesized in the nitrogen atmosphere are with the range of 20~1000nm width and 10 ~100nm thickness, and that nanomaterials are nanoparticles with 20~50nm radius obtained by thermal annealing in an oxygen atmosphere. The crystal structure of the $\beta$-Ga$_2$O$_3$ nanobelts and nanoparticles was in this study investigated by X-ray diffractometer (XRD) and high-resolution transmission electron microscope (HRTEM). The formation processes of the nanobelts and nanoparticles will be discussed in this paper.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.444-445
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• 2007

IZO/Al multilayer anode films for flexible top emitting organic light emitting diodes (TOLEDs) were grown on PEN (polyethylen-enaphthelate) substrate using twin target sputter (TTS) system. To investigate electrical and optical properties of IZO/Al multilayer films, 4-point probe method and UV/Vis spectrometer were used, respectively. From a IZO/Al multilayer films with 100nm-thick Al, sheet resistance of $1.4{\Omega}/{\square}$ and reflectance of above 62% at a range of 500~550nm wavelength could be obtained, In addition, structural and surface properties of IZO/Al multilayer films were analyzed by XRD (X-ray diffraction) and FESEM (field emission scanning electron microscopy) and AES (auger electron spectroscope), respectively. Moreover, flexibility of IZO/Al multilayer anode films were examined by bending test method.

• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.33-36
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• 2010

$MgF_2$ is a current material used for optical applications in the ultraviolet and deep ultraviolet range. Process variables for manufacturing $MgF_2$ thin film were established in order to clarify the optimum conditions for the growth of the thin film, dependant upon the process conditions, and then by changing a number of the vapor deposition conditions, substrate temperatures, and heat treatment conditions, the structural and optical characteristics were measured. Then, optimum process variables were thus derived. Nevertheless, modern applications still require improvement in the optical and structural quality of the deposited layers. In the present work, in order to understand the composition and microstructure of $MgF_2$, single layers grown on a slide glass substrate using an Electron beam Evaporator (KV-660), were analyzed and compared. The surface substrate temperature, having an effect on the quality of the thin film, was changed from $200^{\circ}C$ to $350^{\circ}C$ at intervals of $50^{\circ}C$. The heat treatment temperature, which also has an effect on the thin film, was changed from $200^{\circ}C$ to $400^{\circ}C$ at intervals of $50^{\circ}C$. The physical properties of the thin film were investigated at various fabrication conditions, such as the substrate temperature, the heat treatment temperature, and the heat treatment time, by X-ray diffraction, and field emission-scanning electron microscopy.

• Korean Journal of Metals and Materials
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• v.48 no.7
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• pp.660-666
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• 2010

30 nm thick Ni layers were deposited on a glass substrate by e-beam evaporation. Subsequently, 30 nm or 60 nm ${\alpha}-Si:H$ layers were grown at low temperatures ($<220^{\circ}C$) on the 30 nm Ni/Glass substrate by catalytic CVD (chemical vapor deposition). The sheet resistance, phase, microstructure, depth profile and surface roughness of the $\alpha-Si:H$ layers were examined using a four-point probe, HRXRD (high resolution Xray diffraction), Raman Spectroscopy, FE-SEM (field emission-scanning electron microscopy), TEM (transmission electron microscope) and AES depth profiler. The Ni layers reacted with Si to form NiSi layers with a low sheet resistance of $10{\Omega}/{\Box}$. The crystallinty of the $\alpha-Si:H$ layers on NiSi was up to 60% according to Raman spectroscopy. These results show that both nano-scale NiSi layers and crystalline Si layers can be formed simultaneously on a Ni deposited glass substrate using the proposed low temperature catalytic CVD process.

• Journal of the Korean Vacuum Society
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• v.9 no.2
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• pp.136-143
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• 2000

$SrBi_2Ta_2O_9;(SBT)$ films were deposited on p-type Si(100) at room temperature by rf magnetron sputtering method to confirm the possibility of application of $Pt/SBT/Pt/Ti/SiO_2/Si$ structure (MFM) for destructive read out ferroelectric RAM (random access memory). Their structural characteristics with the various annealing times and Ar/$O_2$ gas flow ratios in sputtering were observed by XRD (X-ray diffractometer) and the surface morphologies were observed by FE-SEM (field emission scanning electron microscopy), and their electrical properties were observed by P-V (polarization-voltage measurement) and I-V (current-voltage measurement). The Ar/$O_2$ gas flow ratios of sputtering gas were changed from 1 : 4 to 4 : 1 and SBT thin films were deposited at room temperature. The films show (105), (110) peaks of SBT by XRD measurement. SBT thin films deposited at room temperature were crystallized by furnace annealing at 80$0^{\circ}C$ in oxygen atmosphere during either one hour or two hours. Among their electrical properties, P-V curves showed shaped hysteresis curves, but the SBT thin films showed the asymmetric ferroelectric properties in P-V curves. When Ar/$O_2$ gas flow ratios are 1 : 1, 2: 1, the leakage current density values of SBT thin films are good, those values of 3 V, 5 V, and 7 V are respectively $3.11\times10^{-8} \textrm{A/cm}^2$, $5\times10^{-8}\textrm{A/cm}^2$, $7\times10^{-8}\textrm{A/cm}^2$.After two hours of annealing time, their electrical properties and crystallization are improved.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.590-592
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• 2010

Li-Mn spinel ($LiMn_2O_4$) is prepared by a hydrothermal process with K-Birnessite ($KMnO_4{\cdot}yH_2O$) as a precursor. The K-Birnessite obtained via a hydrothermal process with potassium permanganate [$KMnO_4$] and urea [$CO(NH_2)_2$] as starting materials are converted to Li-Mn spinel nanoparticles reacting with LiOH. The molar ratio of LiOH/K-Birnessite is adjusted in order to find the effect of the ratio on the structural, morphological and electrochemical performances of the Li-Mn spinel. X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), and thermogravimetry (TG) are used to investigate the crystal structure and morphology of the samples. Galvanostatic charge and discharge are carried out to measure the capacity and rate capability of the Li-Mn spinel. The capacity shows a maximum value of $117\;mAhg^{-1}$ when the molar ratio of LiOH/K-Birnessite is 0.8 and decreases with the increase of the ratio. However the rate capability is improved with the increase of the ratio due to the reduction of the particle size.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.471-475
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• 2006

$VO_x$ thin films with the thickness of 450 nm were prepared on a $Pt/Ti/SiO_{2}/Si$ substrate at room temperature by a reactive radio frequency (rf) magnetron sputtering method. The deposition rates of $VO_x$ thin films were investigated as a function of $O_{2}$ concentration and rf power. As the $O_{2}$ concentration in a $O_{2}/Ar$ mixture increased, the deposition rate decreased. However, the deposition rate increased with increasing rf power. The deposited $VO_x$ thin films were annealed at $450^{\circ}C$ for 2, 4, and 6 h in $O_{2}$ and $N_{2}$ ambient. After annealing, the phase changes of $VO_x$ thin films were investigated using X-ray diffraction analysis. The plane and cross-sectional views of $VO_x$ thin films before and after annealing were observed by field emission scanning electron microscopy. The metal-insulator transition (MIT) properties of $VO_x$ thin films were measured using current-voltage measurement. The excellent MIT properties were observed in $VO_x$ thin films annealed in $O_{2}$ ambient.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.3
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• pp.110-114
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• 2017

$NiO/NiCo_2O_4$ nanocubes were successfully synthesized via the calcination process of $Ni_3[Co(CN)_6]_2$ PBAs. The prepared monodispersed $Ni_3[Co(CN)_6]_2$ PBAs were aggregated by 'self-assembly' of the nuclei generated during the synthesis reaction. The self-assembly rate of the particles is affected by the temperature and the amount of surfactant SDBS (sodium dodecylbenzenesulfonate). FESEM analysis shows that monodispersed 200 nm PBA nanocubes are obtained at 0.25 g SDBS and $60^{\circ}C$ temperature. Thermal behavior was confirmed by thermogravimetric-differential thermal analysis (TG-DTA) to determine optimal calcination conditions. Then, field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) analyzes were performed to investigate the morphology and crystallinity of the particles precursors and $NiO/NiCo_2O_4$ nanocubes.

• Journal of the Korean Chemical Society
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• v.60 no.1
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• pp.34-38
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• 2016

In this paper, zinc oxide nanoparticles (ZnO NPs) were synthesized using the sonochemical method, where equimolar amounts of zinc acetate dehydrate and sodium hydroxide were separately dissolved in deionized water, and then mixed for 30 min under magnetic stirring. The resultant white gel was sonicated for 60, 120, 180, 240, and 360 min with magnetic stirring. The obtained precipitates were centrifuged, repeatedly washed with ethanol to remove ionic impurities, and dried at 50 ℃ for 24 h. The formation of pure NPs was confirmed by X-ray diffraction, and their crystallinity and crystal phases were analyzed as well. Structural investigation was carried out by field-emission scanning electron microscopy (FE-SEM). The photocatalysis behavior of the ZnO NPs was investigated in a dark room under UV irradiation, using Rhodamine B. Spherical, rod, and flower-like ZnO NPs could be obtained by adjusting the sonication time, as observed by FE-SEM. The flower-like ZnO NPs exhibited excellent photocatalytic activity.

• Journal of the Korean Vacuum Society
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• v.19 no.3
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• pp.236-241
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• 2010

ZnO nanorods were grown on ZnO seed layer by hydrothermal method. The ZnO seed layer was coated by sol-gel method, and then the ZnO nanorods on ZnO seed layer were grown with different precursor concentrations ranging from 0.01 M to 0.3 M. FE-SEM (field-emission scanning electron microscopy), XRD (X-ray diffraction), and PL (photoluminescence) were employed to investigate the structural and optical properties of the ZnO nanorods. The diameter and length of ZnO nanorods are increased and also the optical properties are enhanced as the precursor concentrations are increased.