• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.121-121
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• 2010

ZnO is a promising material for the application of high efficiency light emitting diodes with short wavelength region for its large bandgap energy of 3.37 eV which is similar to GaN (3.39 eV) at room temperature. The large exciton binding energy of 60 meV in ZnO provide provides higher efficiency of emission for optoelectronic device applications. Several ZnO/ZnMgO multiple quantum well (MQW) structures have been grown on various substrates such as sapphire, GaN, Si, and so on. However, the achievement of high quality ZnO/ZnMgO MQW structures has been somehow limited by the use of lattice-mismatched substrates. Therefore, we propose the optical properties of ZnO/ZnMgO multiple quantum well (MQW) structures with different well widths grown on lattice-matched ZnO substrates by molecular beam epitaxy. Photoluminescence (PL) spectra show MQW emissions at 3.387 and 3.369 eV for the ZnO/ZnMgO MQW samples with well widths of 2 and 5 nm, respectively, due to the quantum confinement effect. Time-resolved PL results show an efficient photo-generated carrier transfer from the barrier to the MQWs, which leads to an increased intensity ratio of the well to barrier emissions for the ZnO/ZnMgO MQW sample with the wider width. From the power-dependent PL spectra, we observed no PL peak shift of MQW emission in both samples, indicating a negligible built-in electric field effect in the ZnO/$Zn_{0.9}Mg_{0.1}O$ MQWs grown on lattice-matched ZnO substrates.

• 한국전기전자재료학회논문지
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• 제27권7호
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• pp.468-471
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• 2014

The effects of ZnO coating on the sensing properties of CNT:ZnO based gas sensors were studied for $H_2S$ gas. The nano ZnO sensing materials were grown by hydrothermal reaction method. CNT:ZnO was prepared by ball-mill method. The mole range of nano ZnO coating on CNT surface was from 0 to 10%. The CNT:ZnO gas sensors were fabricated by a screen printing method on alumina substrates. The structural and morphological properties of the CNT:ZnO sensing materials were investigated by XRD, EDS, SEM and TEM. The XRD patterns showed that CNT:ZnO powders with hexagonal structure were grown with (002) dominant peak. The diameter of CNT from TEM was about 28 nm.

• 한국재료학회지
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• 제15권10호
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• pp.678-682
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• 2005

We studied the possibility of $Zn_4O(Ac)_2(OH)$ formation as a precursor for ZnO nano particles in sol-gel method. Four different additives such as tetra methyl ammonium hydroxide, mono ethanol amine (MEA), LiOH, and $H_2O$ were used for zinc acetate dissolved in 2-methoxy ethanol. ZnO particles of 5-6 nm in size were observed. Existence of $Zn_4O(Ac)_6$ was not verified. $Zn_4O(Ac)_2(OH)$ molecules were observed and they were believed to be the precursors of ZnO. A peak at 275nm in UV-Vis analysis was observed In the case of MEA and $H_2O$ but no ZnO particles were detected in transmission electron microscopy.

• Journal of Magnetics
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• 제21권3호
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• pp.308-314
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• 2016

Cobalt-, zinc-, and nickel-zinc-substituted nano-size manganese ferrite powders, $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, $Mn_{0.8}Zn_{0.2}Fe_2O_4$ and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$, were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently studied. The $MnFe_2O_4$ ferrite powder annealed at temperatures above 523 K exhibited a spinel structure, and the particle size increased as the annealing temperature increased. All ferrites annealed at 773 K showed a single spinel structure, and the lattice constants and particle size decreased with the substitution of Co, Zn, and Ni-Zn. The $M{\ddot{o}}ssbauer$ spectrum of the $MnFe_2O_4$ ferrite powder annealed at 523 K only showed a doublet due to its superparamagnetic phase, and the $M{\ddot{o}}ssbauer$ spectra of the $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, and $Mn_{0.8}Zn_{0.2}Fe_2O_4$ ferrite powders annealed at 773 K could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. However, the $M{\ddot{o}}ssbauer$ spectrum of the $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$ ferrite powder annealed at 773 K consisted of two Zeeman sextets and one quadrupole doublet due to its ferrimagnetic and paramagnetic behavior. The area ratio of the $M{\ddot{o}}ssbauer$ spectra could be used to determine the cation distribution equation, and we also explained the variation in the $M{\ddot{o}}ssbauer$ parameters by using this cation distribution equation, the superexchange interaction and the particle size. Relative to pure $MnFe_2O_4$, the saturation magnetizations and coercivities were larger in $Mn_{0.8}Co_{0.2}Fe_2O_4$ and smaller in $Mn_{0.8}Zn_{0.2}Fe_2O_4$, and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$. These variations could be explained using the site distribution equations, particle sizes and magnetic moments of the substituted ions.

• 한국정밀공학회지
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• 제28권12호
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• pp.1419-1424
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• 2011

Nanoimprint lithography is a next generation lithography technology, which enables to fabricate nano to micron-scale patterns through simple and low cost process. Nanoimprint lithography has been applied in various industry fields such as light emitting diodes, solar cells and display. Functional patterns, including anti-reflection moth-eye pattern, photonic crystal pattern, fabricated by nanoimprint lithography are used to improve overall efficiency of devices in that fields. For these reasons, in this study, sub-micron-scaled functional patterns were directly fabricated on Si and glass substrates by thermal imprinting process using ZnO nano-particles dispersion resin. Through the thermal imprinting process, arrays of sub-micron-scaled pillar and hole patterns were successfully fabricated on the Si and glass substrates. And then, the topography, components and optical property of the imprinted ZnO nano-particles/resin patterns are characterized by Scanning Electron Microscope, Energy-dispersive X-ray spectroscopy and UV-vis spectrometer, respectively.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.5.2-5.2
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• 2009

From 10 years ago, the development of nano-devices endeavored to achieve reconstruction of information technology (IT) and nano technology (NT) industry. Among the many materials for the IT and NT industry, zinc oxide (ZnO) is a very promising candidate material for the research of nano-device development. Nano-structures of ZnO-based materials were grown easily via various methods and it attracts huge attention because of their superior electrical and optical properties for optoelectronic devices. Recently, among the various growth methods, MOCVD has attracted considerable attention because it is suitable process with benefits such as large area growth, vertical alignment, and accurate doping for nano-device fabrication. However, ZnO based nanowires grown by MOCVD process were had the principal problems of 1st interfacial layers between substrate and nanowire, 2nd a broad diameter (about 100 nm), and 3rd high density, and 4th critical evaporation temperature of Zinc precursors. In particular, the growth of high performance nanowire for high efficiency nano-devices must be formed at high temperature growth, but zinc precursors were evaporated at high temperature.These problems should be repaired for materialization of ultra high performance quantum devices with quantum effect. For this reason, we firstly proposed the growth method of vertical aligned slim MgZnO nanowires (< 10 nm) without interfacial layers using self-phase separation by introduced Mg at critical evaporation temperature of Zinc precursors ($500^{\circ}C$). Here, the self-phase separation was reported that MgO-rich and the ZnO-rich phases were spontaneously formed by additionally introduced Mg precursors. In the growth of nanowires, the nanowires were only grown on the wurzite single crystal seeds as ZnO-rich phases with relatively low Mg composition (~36 at %). In this study, we investigated the microstructural behaviors of self-phase separation with increasing the Mg fluxes in the growth of MZO NWs, in order to secure drastic control engineering of density,diameter, and shape of nanowires.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.204.1-204.1
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• 2013

Fluorine, the radius of which is close to that of oxygen, could be an appropriate anion doping candidate. A lower lattice distortion could be expected for F doping, compared with Al, Ga, and In doping. F-doped ZnO (FZO) and undoped ZnO nanorods were grown onto glass substrate by the hydrothemal method. The doping level in the solution, designated by F/Zn atomic ratio of was varied from 0.0 to 10.0 in 2.0 steps. To investigate the effects of the structure and optical properties of FZO nanorods were investigated using X-ray diffraction, UV-visible spectroscopy and photoluminescence (PL). For the PL spectra, the maximum peak position of NBE moves to higher energy, from 0 to 4 at.%. As the doping concentration increases, the maximum peak position of NBE gradually moves to lover energy, from 4 to 10 at.%.

• 한국세라믹학회지
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• 제56권4호
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• pp.354-359
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• 2019

Information security films that can ensure personal privacy by reducing the viewing angle of display screens were fabricated by microlouver patterning and a ZnO nano-ink filling process. Optical simulation results demonstrated that all the microlouver films showed good security performances. Security performances were evaluated as calculated relative luminance ratios compared between the side and front. Based on the simulation results, microlouver films were fabricated by UV imprint lithography and nano-ink bar coating. However, distortion of the microlouver pattern occurred with the use of high-viscosity nano-inks such as ZrO₂ and TiO₂, and the CuO-filled microlouver film suffered from very low optical transmittance. Accordingly, the effects of ZnO filling height on security performance were intensively investigated through simulation and experimental measurements. The fabricated microlouver film with a 75-㎛-high ZnO filling exhibited a good relative luminance ratio of 0.75 at a 60° side angle and a transmittance of 44% at a wavelength of 550 nm.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2008년도 춘계학술발표대회 및 제14회 신소재 심포지엄
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• pp.25.2-25.2
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• 2008

• 한국전기전자재료학회논문지
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• 제25권9호
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• pp.717-722
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• 2012

In this work, we study on the effects of the oxygen pressure on the structural and crystalline of MgZnO thin films. MgZnO thin films were deposited on p-Si (111) substrates by using pulsed laser deposition. The X-ray diffraction analysis and energy-dispersive X-ray results revealed that as the oxygen pressure increased and Mg content in the MgZnO films decreased. Also Crystal structure was changed from cubic rock salt to hexagonal wurtzite. Alpha step and atomic force microscopy results showed that the thickness of the films are about 100 nm, and it has been found that the MgZnO (002) preferred orientation were deposited with increasing the oxygen pressure. Therefore, the effect of the preferred orientation, the crystallization grew in the form of the columnar; Grain size and RMS of the films were increased with increasing oxygen pressure.