• 한국전기전자재료학회논문지
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• 제21권12호
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• pp.1083-1089
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• 2008

We studied the dielectric characteristics of low-k SiOCH thin films by Ellipsometry. The SiOCH thin films were prepared by deposition of BTMSM precursors on p-Si wafer by CCP-PECVD method. The nano-porous structural organic/inorganic hybrid-type of SiOCH thin films correlated directly to the formation of low dielectrics close to pore(k=1). The structural groups including highly dense pores in SiOCH thin films originated the anisotropic geometry type of network structure directing to complex refractive characteristics of SiOCH single layer on the p-Si wafer. The linearly polarized beam of Xe-ramp in the range from 190 nm to 2100 nm introduced to the surface of SiOCH thin film, and the reflected beam was Elliptically polarized by complex refractive coefficients of SiOCH dipole groups. The amplitude variation $\Psi$ and phase variation $\Delta$ of the relative reflective coefficients between perpendicular and parallel components to the incident plane were measured by Ellipsometry. The complex optical constants n and k as well as the dielectric constant and thickness of SiOCH thin films were driven by the measured value of $\Psi$ and $\Delta$.

• 한국전기전자재료학회논문지
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• 제23권8호
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• pp.581-586
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• 2010

The porous Si (PS) was annealed at various temperature in air, argon, and nitrogen atmosphere. Structural and optical properties of the annealed PS were investigated by scanning electron microscopy (SEM) and photoluminescence (PL). It is found that the shape of pore is changed from circle to channel as increasing annealing temperature which was annealed in air and argon atmosphere. In case of PS annealed in nitrogen atmosphere, the shape of pore is changed from channel to circle with increase annealing temperature from 600 to $800^{\circ}C$. The PL peak position is blue-shifted with increasing annealing temperature. As annealing temperature increases, the PL intensity of the PS annealed in argon is decreased but that of the PS annealed in nitrogen is increased. It might be due to the formation of Si-N bonds and it passivates the non-radiative centers which is Si dangling bonds on the surface of the PS.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.108-109
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• 2012

This talk will begin with the demonstration of facile synthesis of silicon nanostructures using the magnesiothermic reduction on silica nanostructures prepared via self-assembly, which will be followed by the characterization results of their performance for energy storage. This talk will also report the fabrication and characterization of highly porous, stretchable, and conductive polymer nanocomposites embedded with carbon nanotubes (CNTs) for application in flexible lithium-ion batteries. It will be presented that the porous CNT-embedded PDMS nanocomposites are capable of good electrochemical performance with mechanical flexibility, suggesting these nanocomposites could be outstanding anode candidates for use in flexible lithium-ion batteries. Directed self-assembly (DSA) of block copolymers (BCPs) can generate uniform and periodic patterns within guiding templates, and has been one of the promising nanofabrication methodologies for resolving the resolution limit of optical lithography. BCP self-assembly processing is scalable and of low cost, and is well-suited for integration with existing semiconductor manufacturing techniques. This talk will introduce recent research results (of my research group) on the self-assembly of Si-containing block copolymers for the achievement of sub-10 nm resolution, fast pattern generation, transfer-printing capability onto nonplanar substrates, and device applications for nonvolatile memories. An extraordinarily facile nanofabrication approach that enables sub-10 nm resolutions through the synergic combination of nanotransfer printing (nTP) and DSA of block copolymers is also introduced. This simple printing method can be applied on oxides, metals, polymers, and non-planar substrates without pretreatments. This talk will also report the direct formation of ordered memristor nanostructures on metal and graphene electrodes by the self-assembly of Si-containing BCPs. This approach offers a practical pathway to fabricate high-density resistive memory devices without using high-cost lithography and pattern-transfer processes. Finally, this talk will present a novel approach that can relieve the power consumption issue of phase-change memories by incorporating a thin $SiO_x$ layer formed by BCP self-assembly, which locally blocks the contact between a heater electrode and a phase-change material and reduces the phase-change volume. The writing current decreases by 5 times (corresponding to a power reduction of 1/20) as the occupying area fraction of $SiO_x$ nanostructures varies.

• Korean Membrane Journal
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• 제3권1호
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• pp.69-74
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• 2001

Films of TiO$_2$/SiO$_2$ were deposited on the inner surface of the porous glass support tubes by decomposition of tetraisopropyl titanate (TIPT) and tetraethyl orthosilicate (TEOS) at atmospheric pressure. Dense and hydrogen -permselective membranes were formed at 400-600$\^{C}$. The permeation rates of H$_2$ through the membrane at 600$\^{C}$ were 0.2-0.4 ㎤(STP)/min-㎠ atm and H$_2$:N$_2$permeation ratios were above 1000. The permeation properties of the membranes were investigated at various deposition temperatures and TIPT/TEOS concentrations. Decomposition of TIPT alone at temperatures above 400$\^{C}$ produced porous crystalline TiO$_2$ films and they were not H7-selective. Decomposition of TEOS produced H$_2$-permeable SiO$_2$ films at 400-600$\^{C}$ but film deposition rate was very low. Addition of TIFT to the TEOS stream significantly accelerated the deposition rate and produced highly H$_2$-selective films. Increasing the TIPT/TEOS concentration ratio increased the deposition rate. The TiO$_2$/SiO$_2$ membranes formed at 600 $\^{C}$ have the permeation properties comparable to those of SiO$_2$ membranes produced from TEOS.

• 한국세라믹학회지
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• 제34권2호
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• pp.216-224
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• 1997

TEOS와 에탄올의 양을 고정하고 H2O/TEOS의 몰비가 2.6-59.0이 되는 범위에서 염산촉매를 사용하여 다공성 실리카 세라믹을 제조하였다. 서로 다른 조성의 솔 9종을 만든 후 젤화시간 측정, TG/DTA에 의한 건조시료의 열분석 및 FT-IR과 X-ray diffractometer에 의한 중간생성물의 특성분석을 수행하였고 50$0^{\circ}C$까지 열처리한 시료의 FT-IR에 의한 SiO2폴리머 분석, N2-adsorption isotherm을 이용한 비표면적과 기공크기분포 조사 및 TEM에 의한 SiO2폴리머의 형태와 기공의 변화를 조사하였다. 적용된 조성 및 촉매의 농도에서 최소 젤화반응시간은 TEOS1몰달 물의 양이 약 11몰에서, 가장 높은 중합도는 약 8-18몰에서, 그리고 가장 큰 비표면적값은 약 11몰에서 보였다. 이것은 물의 양이 약 11몰일 때 중합반응이 가장 빠르게 진행하였음을 의미한다. 결론적으로, 물의 양이 증가함에 따라서 약 11몰까지는 반응이 빠르게 진행되나 그 이상의 물이 사용될 경우 과잉의 물이 반응저해요인으로 작용하여 젤화시간의 지연 및 비표면적의 감소를 보인다.

• 한국재료학회지
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• 제14권2호
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• pp.133-140
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• 2004

We carried out anodic aluminum oxide (AAO) on a Si and a sapphire substrate. For anodic oxidation of Al two types of specimens prepared were Al(0.5 $\mu\textrm{m}$)!Si and Al(0.5 $\mu\textrm{m}$)/Ti(0.1 $\mu\textrm{m}$)$SiO_2$(0.1 $\mu\textrm{m}$)/GaN(2 $\mu\textrm{m}$)/Sapphire. Surface morphology of Al film was analyzed depending on the deposition methods such as sputtering, thermal evaporation, and electron beam evaporation. Without conventional electron lithography, we obtained ordered nano-pattern of porous alumina by in- situ process. Electropolishing of Al layer was carried out to improve the surface morphology and evaluated. Two step anodizing was adopted for ordered regular array of AAO formation. The applied electric voltage was 40 V and oxalic acid was used as an electrolyte. The reference electrode was graphite. Through the optimization of process parameters such as electrolyte concentration, temperature, and process time, a regular array of AAO was formed on Si and sapphire substrate. In case of Si substrate the diameter of pore and distance between pores was 50 and 100 nm, respectively. In case of sapphire substrate, the diameter of pore and distance between pores was 40 and 80 nm, respectively

• Advances in nano research
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• 제7권5호
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• pp.325-335
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• 2019

In the present study, nonlocal strain gradient theory (NSGT) is developed for wave propagation of functionally graded (FG) nanoscale plate in the thermal environment by considering the porosity effect. $Si_3N_4$ as ceramic phase and SUS304 as metal phase are regarded to be constitutive material of FG nanoplate. The porosity effect is taken into account on the basis of the newly extended method which considers coupling influence between Young's modulus and mass density. The motion relation is derived by applying Hamilton's principle. NSGT is implemented in order to account for small size effect. Wave frequency and phase velocity are obtained by solving the problem via an analytical method. The effects of different parameters such as porosity coefficient, gradient index, wave number, scale factor and temperature change on phase velocity and wave frequency of FG porous nanoplate have been examined and been presented in a group of illustrations.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1998년도 IUMRS-ICEM ABSTRACT BOOK
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• pp.94.1-94
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• 1998

• 한국입자에어로졸학회지
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• 제8권4호
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• pp.173-180
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• 2012

SiC particles, 8.3 ${\mu}m$ in volume average diameter, were chlorinated in an alumina tubular reactor, 2.4 cm in diameter and 32 cm in length, with reactor temperature varied from 100 to $1200^{\circ}C$. The flow rate of the gas admitted to the reactor was held constant at 300 cc/min, the mole fraction of chlorine in the gas at 0.1 and the reaction time at 4 h. The chlorination was negligibly small up to the temperature of $500^{\circ}C$. Thereafter, the degree of chlorination increased remarkably with increasing temperature until $900^{\circ}C$. As the temperature was increased further from 900 to $1200^{\circ}C$, the increments in chlorination degree were rather small. At $1200^{\circ}C$, the chlorination has nearly been completed. The surface area of the residual carbon varied with chlorination temperature in a manner similar to that with the variation of chlorination degree with temperature. The surface area at $1200^{\circ}C$ was 912 $m^{2}/g$. A simple model was developed to predict the conversion of a SiC under various conditions. A Langmuir-Hinshelwood type rate law with two rate constants was employed in the model. Assuming that the two rate constants, $k_{1}$ and $k_{2}$, can be expressed as $A_{1e}^{-E_{1}/RT}$ and $A_{2e}^{-E_{2}/RT}$, the four parameters, $A_{1}$, $E_{1}$, $A_{2}$, and $E_{2}$ were determined to be 32.0 m/min, 103,071 J/mol, 2.24 $m^{3}/mol$ and 39,526 J/mol, respectively, through regression to best fit experimental data.

• 한국세라믹학회지
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• 제51권5호
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• pp.511-515
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• 2014

The thermodynamic instability of bubbles in wet-foam colloidal suspension is due to the substantial area of their gas/liquid interface. Several physical processes lead to gas diffusion from smaller to larger bubbles, resulting in a coarsening and Ostwald ripening of wet foam. This includes a narrowing of the bubble size distribution. The distribution and microstructure of porous ceramics, the adsorption free energy and Laplace pressure of $Al_2O_3$ particle-stabilized colloidal suspension, and $SiO_2$ content were investigated for tailoring the bubble size. Wet-foam stability of more than 80% is related to the degree of hydrophobicity with contact angles of $62-70^{\circ}$ achieved from the surfactant. The contact angle replaces part of the highly energetic interface and lowers the free energy of the system. This leads to an apparent increase in the surface tension (26-33 mN/m) of the colloidal suspension.