• Korean Journal of Materials Research
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• v.21 no.5
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• pp.273-276
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• 2011

Ultraviolet (UV) light emitting diodes (LEDs) were grown on a patterned n-type GaN substrate (PNS) with 200 nm silicon-di-oxide (SiO2) nano pattern diameter to improve the light output efficiency of the diodes. Wet etched self assembled indium tin oxide (ITO) nano clusters serve as a dry etching mask for converting the SiO2 layer grown on the n-GaN template into SiO2 nano patterns by inductively coupled plasma etching. PNS is obtained by n-GaN regrowth on the SiO2 nano patterns and UV-LEDs were fabricated using PNS as a template. Two UV-LEDs, a reference LED without PNS and a 200 nm PNS UV-LEDs were fabricated. Scanning Electron microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Photoluminescence (PL) and Light output intensity- Input current- Voltage (L-I-V) characteristics were used to evaluate the ITO-$SiO_2$ nanopattern surface morphology, threading dislocation propagation, PNS crystalline property, PNS optical property and UVLED device performance respectively. The light out put intensity was enhanced by 1.6times@100mA for the LED grown on PNS compared to the reference LED with out PNS.

• The Journal of the Petrological Society of Korea
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• v.3 no.2
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• pp.156-170
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• 1994

The talc ore deposits can be divided into chloritic and dolomitic ores according to mineral assemblages. The former is mainly composed of chlorite and talc accompanied with dolomite, muscovite and opaque mineral, and the latter of dolomite and talc with serpentine, calcite and magnesite in places. Talc was originated from chlorite and serpentine. Carbonate minerals were formed either directly from the introduced hydrothermal solution or secondarily as a by-product of steatitization of chlorite and serpentine. The process of talc formation may be governed by the chemical composition of the host rocks and the amount and/or chemical composition of the hydrothermal solution which may be different in places. However, the representative reactions producing talc from chlorite and serpentine are as follows : (1) chlorite+$Mg^{++}+Si^{4+}+H_2O$=talc, (2) chlorite+$Mg^{++}+Si^{4+}+Ca^{++}+CO_2+O_2+H_2O$=talc+ dolomite+ magnesite, and (3) serpentine +$Mg^{++}+Fe^{++}+Si^{4+}+Ca^{++}+CO_2+H_2O$=talc+dolomite. The reactions indicate that the carbonate minerals can be formed when the hydrothermal solution have high $fO_2$ and $fCO_2$. The steatitization might be proceeded by the hydrothermally metasomatic reaction between chlorite schist or chlorite gneiss intercalated in the granitic gneiss and hydrothermal solution accompanied to the wet granitization.

• Journal of the Korean Ceramic Society
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• v.42 no.5 s.276
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• pp.333-337
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• 2005

In order to improve the performance of green emitting phosphors for plasma display panel, the $Zn_2SiO_4:Mn,Al$ phosphors were synthesized using sol-gel technique and studied using SEM and VUV photoluminescence spectrometer. pH values of the starting solutions (pH = 0.5$\~$2.34) were controled by HCl as the catalysis of hydrolysis and wet gels were dried at $80^{\circ}C$ and $120^{\circ}C$, respectively. We investigated the effects of pH and drying temperatures during sol-gel processes. The results indicated that the phosphor prepared at pH = 1 showed the maximum emission intensity in both drying conditions and the effect of pH of the starting solution on morphology were increased with particle size as HCl and phosphor dried at high temperature showed more spherical and smaller particles than at low.

• Journal of the Korean Ceramic Society
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• v.53 no.6
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• pp.604-609
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• 2016

This study reports on wet-foam stability with respect to porous ceramics from a particle-stabilized colloidal suspension that is achieved through the addition of polymethyl methacrylate (PMMA) using a wet process. To stabilize the wet foam, an initial colloidal suspension of $Al_2O_3$ was partially hydrophobized by the surfactant propyl gallate (2 wt.%) and $SiO_2$ was added as a stabilizer. The influence of the PMMA content on the bubble size, pore size, and pore distribution in terms of the contact angle, surface tension, adsorption free energy, and Laplace pressure are described in this paper. The results show a wet-foam stability of more than 83%, which corresponds to a particle free energy of $2.7{\times}10^{-12}J$ and a pressure difference of 61.1 mPa for colloidal particles with 20 wt.% of PMMA beads. It was possible to control the uniform distribution of the open/closed pores by increasing the PMMA content and by adding thick struts, leading to the achievement of a higher-stability wet foam for use in porous ceramics.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.249-254
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• 1998

The etching experiments for n-GaN were done using the wet chemical, photo-enhanced-chemical and electro-chemical etching methods. The experimental results show that n-GaN is etched is diluted NaOH solution at room temperature and the removed thickness of n-GaN is linearly increased with etching times. The etching rate of the photo-enhanced-chemical and electro-chemical etching methods are several times higher than that of the wet chemical method. The maximum etching rate of n-GaN with $n{\fallingdotseq}1{\times}10^{19}cm^{-3}$ was 164 $\AA$/min under the experimental condition of the Photo-enhanced-chemical etching. The etching rates of n-GaN are very much dependant on the electron concentrations of the samples. The pattern is $100{\mu}m{\times}100{\mu}m$ rectangulars covered with $SiO_2$film. It is shown that the etched side-wall charactistics of the pattern is vertical without dependance of the n-GaN orientations, and the smoothness of etched n-GaN surface is fairly flat.

• Korean Journal of Metals and Materials
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• v.47 no.7
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• pp.423-432
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• 2009

In the galvanizing coating process, the effects of the silicon content on the coatability and wettability of molten zinc were investigated on Dual-Phase High Strength Steels (DP-HSS) with various Si contents using the galvanizing simulator and dynamic reactive wetting systems. DP-HSS showed good coatability and a well-developed inhibition layer in the range of Si content below 0.5 wt%. Good coatability was the results of the mixed oxide $Mn_{2}SiO_{4}$, being formed by the selective oxidation on the surface, with a low contact angle in molten zinc and a large fraction of oxide free surface that provided a sufficient site for the molten zinc to wet and react with the substrate. On the other hand, with more than 0.5 wt%, DP-HSS exhibited poor coatability and an irregularly developed inhibition layer. The poor coatability was due to the poor wettability that resulted from the development of network-type layers of amorphous ${SiO}_{2}$, leading to a high contact angle in molten zinc, on the surface.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.3
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• pp.234-239
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• 2007

This paper describes the TiW ohmic contact characteristics under the surface treatment of the polycrystalline 3C-SiC thin film grown on $SiO_2/Si(100)$ wafers by APCVD. The poly 3C-SiC surface was polished by using CMP(chemical mechanical polishing) process and then oxidized by wet-oxidation process, and finally removed SiC oxide layers. A TiW thin film as a metalization process was deposited on the surface treated poly 3C-SiC layer and was annealed through a RTA(rapid thermal annealing) process. TiW/poly 3C-SiC was investigated to get mechanical, physical, and electrical characteristics using SEM, XRD, XPS, AFM, optical microscope, I-V characteristic, and four-point probe, respectively. Contact resistivity of the surface treated 3C-SiC was measured as the lowest $1.2{\times}10^{-5}{\Omega}cm^2$ at $900^{\circ}C$ for 45 sec. Therefore, the surface treatments of poly 3C-SiC are necessary to get better contact resistance for extreme environment MEMS applications.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.401-401
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• 2011

In this work, we deposited Al2O3doped ZnO (AZO) thin films by direct current (DC) magnetron sputtering method with a $40^{\circ}$ tilted target, for application in the front layer of thin film solar cell. Wet chemical etching behavior of AZO films was also investigated. In order to optimize textured AZO films, oxalic acid ($C_2H_2O_4$)has been used as wet etchant of AZO film. In this experiment we used 0.001% concentration of oxalic acid various etching time, that showed an anisotropy in etching texture of AZO films. Electrical resistivity, Hall mobility and carrier concentration measurements are performed by using the Hall measurement, that are $6{\times}10^{-4}{\Omega}cm$, $20{\sim}25cm^2/V-s$ and $4{\sim}6{\times}10^{20}$, respectively.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.126-126
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• 2003

유기트랜지스터에 관한 연구는 1980년 이후부터 시작되었으나 근래에 들어 전 세계적으로 본격적인 연구가 진행되고 있다. 제작공정이 간단하고 비용이 저렴하며 충격에 의해 깨지지 않고 구부리거나 접을 수 있는 전자 회로 기판이 미래의 산업에 필수적인 요소가 될 것으로 예상되고 있으며 이러한 요구를 충족시킬 수 있는 유기트랜지스터의 개발은 아주 중요한 연구분야로 대두되고 있다. 본 연구에서는 표면처리에 따른 contact angle, I-V 특성곡선, 표면 morphology 등의 결과로부터 dry cleaning 한 것이 wet cleaning한 것보다 왜 좋은지를 논하고자 한다. 먼저 N-type SiO$_2$ 기판을 이용하여 back면의 oxide층을 제거한 후, back gate용으로 사용하기 위하여 sputtering장치로 Au/Cr을 증차하였다. 그리고 기판에 앞면을 photolithography 공정을 이용하여 Au/Cr를 1000$\AA$ 증착 하여 source-, drain-eldctrode를 제조하였다. 그리고 SiO$_2$ 기판의 표면처리를 달리하여 그 위에 유기박막을 증착하여 특성을 비교하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.3
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• pp.185-191
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• 2017

Cadmium compounds with one dimension (1D) nanostructures have attracted attention for their excellent electrical and optical properties. In this study, vertically aligned CdTe-Si nanostructures with high density were synthesized by several simple chemical reactions. First, l D Te nanostructures were synthesized by silver assisted chemical Si wafer etching followed by a galvanic displacement reaction of the etched Si nanowires. Nanowire length was controlled from 1 to $25{\mu}m$ by adjusting etching time. The Si nanowire galvanic displacement reaction in $HTeO_2{^+}$ electrolyte created hybrid 1D Te-branched Si nanostructures. The sequential topochemical reaction resulted in $Ag_2Te-Si$ nanostructures, and the cation exchange reaction with the hybrid 1D Te-branched Si nanostructures resulted in CdTe-Si nanostructures. Wet chemical processes including metal assisted etching, galvanic displacement, topochemical and cation exchange reactions are proposed as simple routes to fabricate large scale, vertically aligned CdTe-Si hybrid nanostructures with high density.