• KIEE International Transactions on Electrophysics and Applications
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• v.5C no.2
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• pp.54-57
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• 2005

Photoreflectance (PR) has been measured to investigate the characterization of the Si$_{3}$N$_{4}$Al$_{0.21}$ Ga$_{0.79}$As/GaAs and Al$_{0.21}$Ga$_{0.79}$As/GaAs heterostructures. In the PR spectrum, the caplayer thickness was 170 nm and Si$_{3}$N$_{4}$ was utilized as the capping material. The C peak is confirmed as the carbon defect with residual impurity originating from the growth process. After annealing, in the presence of the Si$_{2}$N$_{4}$ cap layer, band gap energy was low shifted. This result indicates that the Si$_{3}$N$_{4}$ cap layer controlled evaporation of the As atom.

• Geotechnical Engineering
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• v.3 no.3
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• pp.63-74
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• 1987

A practical constitutive equation with sufficient generality is proposed for porous materials to deal with plastic pore compaction and pore related strain-hardening. With an application of this proposed model, finite element calculations are executed for the compaction of a porous material. Results show powerful potential of finite element method in a quantitative investigation of the process of the compaction. Special attention is given to the process of unloading during which the development of tensile principal stress may lead to phenomena such as lamination and end-capping.

• The Journal of the Korean dental association
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• v.57 no.8
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• pp.464-473
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• 2019

For dental pulp treatment of immature permanent teeth, direct pulp capping or partial/cervical pulpotomy (apexogenesis) procedures can be used if the dental pulp is vital. MTA (Mineral Trioxide Aggregate) is regarded as the first choice dressing material for these procedures because its higher success rate. It can be also used successfully for devitalized dental pulp which has been treated by calcium hydroxide. This apexification procedure with MTA has a few advantage such as short treatment period and increase of resistance against root fracture. Recently, regenerative endodontic treatment was introduced for devitalized immature pulp. It can maintain pulp vitality and lead to continuing root development although the dental pulp was devitalized.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.124-124
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• 2010

Currently, extreme ultraviolet lithography (EUVL) is being investigated for next generation lithography. EUVL is one of competitive lithographic technologies for sub-22nm fabrication of nano-scale Si devices that can possibly replace the conventional photolithography used to make today's microcircuits. Among the core EUVL technologies, mask fabrication is of considerable importance due to the use of new reflective optics having a completely different configuration compared to those of conventional photolithography. Therefore, new materials and new mask fabrication process are required for high performance EUVL mask fabrication. This study investigated the etching properties of SnO2 (Tin Oxide) as a new absorber material for EUVL binary mask. The EUVL mask structure used for etching is SnO2 (absorber layer) / Ru (capping / etch stop layer) / Mo-Si multilayer (reflective layer) / Si (substrate). Since the Ru etch stop layer should not be etched, infinitely high selectivity of SnO2 layer to Ru ESL is required. To obtain infinitely high etch selectivity and very low LER (line edge roughness) values, etch parameters of gas flow ratio, top electrode power, dc self - bias voltage (Vdc), and etch time were varied in inductively coupled Cl2/Ar plasmas. For certain process window, infinitely high etch selectivity of SnO2 to Ru ESL could be obtained by optimizing the process parameters. Etch characteristics were measured by on scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses. Detailed mechanisms for ultra-high etch selectivity will be discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.3-4
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• 2005

Germanium nanocrystals(NCs) were formed in the silicon dioxide($SiO_2$) on Si layers by Ge implantation and rapid thermal annealing process. The density and mean size of Ge-NCs heated at $800^{\circ}C$ during 10 min were confirmed by High Resolution Transmission Electron Microscopy. Capacitance versus voltage(C-V) measurements of MOS capacitors with single $Al_2O_3$ capping layers were performed in order to study electrical properties. The C-V results exhibit large threshold voltage shift originated by charging effect in Ge-NCs, revealing the possibility that the structure is applicable to Nano Floating Gate Memory(NFGM) devices.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05a
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• pp.206-209
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• 2002

본 논문에서는 폴리실리콘의 재결정화 공정에서 발생하기 쉬운 폴리실리콘의 엉김현상, 슬립, 부분적인 실리콘 기판의 녹음현상 등을 방지하기 위한 방법을 제시한다. 그리고 재결정화 된 박막의 질을 향상시키기 위한 폴리실리콘과 보호 산화막(capping oxide)의 두께 변화에 따른 실험 결과를 살펴본다. 폴리실리콘의 엉김현상은 매몰 산화막(buried oxide)과 액체 상태의 실리콘 사이의 wetting angle과 관계되는데, 이를-방지하기 위해서는 재결정화할 폴리실리콘과 산화막의 계면에 질소를 주입시켜주면 되는데, 이는 재결정화할 시료를 암모니아 가스 분위기에서 열처리를 통하여 해결할 수 있다. 그러고 실러콘 기판의 국부적 녹음 현상 및 슬립은 실리콘 기판의 윗면을 mechanical damage에 의해서 약 $20{\mu}m$ 정도의 거칠기를 가지도록 하면 이러한 현상을 방지할 수 있다. 그러고 폴리실리콘이 재결정활 될 때 부피의 변화가 발생하며, 이로 인하여 재결정화된 박막의 두께는 위치에 따라 변화한다. 재결정화된 박막 두께의 균일도를 유지하기 위해서는 재결정화할 폴리실리콘 두께의 3배 이상이 되는 보호 산화막을 사용하였을 때 원하는 균일도를 얻을 수 있었다.

• Journal of Korean Society on Water Environment
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• v.32 no.2
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• pp.216-221
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• 2016

The adsorption characteristics of mixed heavy metals (Cr(III), As(VI)) in aqueous solution were investigated using a sediment amendment composite. Sediment amendment composite was composed of clean sediment (40%), zeolite (20%), recycled aggregate (10%), steel slag (10%), oyster shell (10%), and cement (10%). The experimental results showed that the adsorption equilibrium was attained after 180 mins. Heavy metal adsorption was characterized using Freundlich and Langmuir equations. The equilibrium adsorption data for the sediment amendment composite better fitted with the Langmuir model than the Freundlich model. The maximum adsorption capacity of Cr(VI) (36.07 mg/g) was higher than As(III) (25.54 mg/g); and the adsorption efficiency of the Cr(VI) and As(III) ions solution decreased with decreasing pH from 2 to 10. The collective results suggested that the sediment amendment composite is a promising material for a reactive cap that controls the release of Cr(VI) and As(III) from contaminated sediments.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.6
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• pp.458-461
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• 2019

The facile synthesis of shape-controlled Pd nanoparticles (PdNPs) with ascorbic acid as a reducing agent and cetyltrimethylammonium bromide (CTAB) as a capping agent is presented in this study. The synthesized PdNPs were characterized by UV-vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman Spectroscopy. The prepared PdNPs show efficient surface-enhanced Raman scattering (SERS) properties. SERS studies on the adsorption characteristics of 1,4-phenylene diisocyanide (1,4-PDI) on colloidal PdNPs have revealed that the relative peak intensity of the $(NC)_{free}$ and $(NC)_{bound}$ modes distinctly depends on the 1,4-PDI concentration as well as the shape of the PdNPs. Furthermore, we found that the PdNPs are also efficient photoelectron emitters such that the SERS spectrum of 4-nitrobenzenethiol (4-NBT) on PdNPs is readily converted to that of 4-aminobenzenethiol (4-ABT) under 632.8 nm radiation.

• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.627-636
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• 1993

Anionic acrylic resin utilizing macromer(TBMA-g-MMA) copolymer was synthesized by preparing (TBMA) macromer using anionic living polymerization, followed by graft copolymerization with MMA macromer. To control the anionic site content in graft copolymer, the relative composition((TBMA) macromer/MMA ratio) of the graft copolymer was controlled at 7/3, 10/90, 15/85, 20/80, 30/70, 40/60, 50/50 in weight content. In the course of anionic living polymerization of(TBMA) macromer, broad molecular weight distribution (1.4~1.5) was obtained by using n-butyllithium-diphenyethylene initiatior system at $-78^{\circ}C$. To introduce the double bond at the end of chain in termination step, methacryloyl chloride was reacted after insertion of benzaldehyde as capping material. Moreover, TBMA parts in graft copolymer were hydrolyzed in the presence of p-toluenesulfonic acid catalyst, and neutralization of graft copolymer with triethylamine was granted acrylic resin to anionic site. Molecular weight and molecular weight distribution of(TBMA) macromer were determined by GPC, and the hydrolysis of TBMA with neutralization of acrylic resin were determined by IR and NMR. From water dispersion and stability point of view, stable dispersion state appeared at low molecular weight(TBMA) macromer with a small TBMA content as a result of scrutiny about the relation to TBMA content and branch length for(TBMA) macromer molecular weight in graft copolymer.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.5
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• pp.450-457
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• 2018

To design the practical core-shell electrocatalysts, combination of core and shell materials is important to meet catalytic activity and durability target. In general, Pd is considered as a good core material due to its best activity caused by strain/ligand effect. Preparing Pd nanoparticles can be a starting point in fabricating core-shell type electrocatalysts, much simplified Pd preparing process is suggested by using carbon monoxide (CO) as a reducing agent and/or capping agent. The solvent composition and reaction temperature can control to nanosheet, tetrahedron, and sphere without using additional stabilizer. Among them, Pd nanosheet which has mainly (111) plane showed about 3 times higher electrocatalytic activity for oxygen reduction reaction (ORR) to the spherical Pd nanoparticles. The enhanced ORR activity of Pd nanosheets can be attributed to the exposure of Pd (111) surface and the high electrochemical surface area. Therefore, we demonstrated that the shape of Pd nanomaterials is easily controlled via a facile reduction method using CO, and (111) plane-oriented Pd nanosheets can be a promising ORR catalysts and core material for polymer electrolyte fuel cells (PEFCs).