• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.1-6
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• 2017

Functional coatings, such as anti-reflection and self-cleaning, are frequently applied to cover glass for photovoltaic applications. Anti-reflection coatings made of mesoporous silica film have been shown to enhance the light transmittance. $TiO_2$ photocatalyst films are often applied as a self-cleaning coating. In this study, transparent hydrophobic anti-reflective and self-cleaning coatings made of $SiO_2/TiO_2$ thin layers were fabricated on a slide glass substrate by the sol-gel and dip-coating processes. The morphology of the functional coatings was characterized by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM). The optical properties of the functional coatings were investigated using an UV-visible spectrophotometer. Contact angle measurements were performed to confirm the hydrophobicity of the surface. The results showed that the $TiO_2$ films exhibit a high transmittance comparable to that of the bare slide glass substrate. The $TiO_2$ nanoparticles make the film more reflective and lead to a lower transmittance. However, the transmittance of the $SiO_2/TiO_2$ thin layers is 93.5% at 550 nm with a contact angle of $110^{\circ}$, which is higher than that of the bare slide glass (2.0%).

• Polymer(Korea)
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• v.37 no.3
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• pp.308-315
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• 2013

In this study, we performed surface modification of silica nanoparticles with bis[3-(triethoxysilylpropyl)]tetrasulfide (TESPT) silane coupling agent to study the effects of treatment temperature, treatment time, and amount of TESPT used on the silanization degree with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), elemental analysis (EA) and solid state $^{13}C$ and $^{29}Si$ cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance spectroscopy (NMR). We found peak area of isolated silanol groups at $3747cm^{-1}$ decreased, but peak area of $-CH_2$ asymmetric stretching of TESPT at $2938cm^{-1}$ increased with the amount of TESPT from FTIR measurements. We also used universal testing machine (UTM) to study mechanical properties of styrene butadiene rubber (SBR) nanocomposites with 20 phr (parts per hundred of rubber) of pristine and TESPT modified silicas, respectively. The tensile strength and 100% modulus of modified silica/SBR nanocomposite were enhanced from 5.65 to 9.38MPa, from 1.62 to 2.73 MPa, respectively, compared to those of pristine silica/SBR nanocomposite.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.4
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• pp.147-152
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• 2011

ZnO nanorods fabricated on a Zn substrate pre-coated with ZnO as a seed layer by the hydrothermal method were studied mainly as a function of ZnO precursor concentration. Characteristic features by using field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) were investigated to define the changed micro-structure and crystalline phase of the ZnO nanorods according to the experimental conditions. The nanorod morphology strongly depended on the precursor concentration. For example, ZnO nanorods vertically aligned with a hexagonal (002) oriented structure with a diameter of 600~700 nm and length of $6.75{\mu}m$ were clearly observed at the highest concentration of 0.015 M. The strong hexagonal structure was believed to be associated with the highest photoluminescene (PL) intensity and a promising voltage value of ca. 6.069 V at $1000{\mu}A$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.4
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• pp.159-164
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• 2009

We fabricated 40 nm-thick cobalt silicide ($CoSi_2$) as a buffer layer, on p-type Si(100) and Si(111) substrates to investigate the possibility of GaN epitaxial growth on $CoSi_2$/Si substrates. We deposited GaN using a HVPE (hydride vapor phase epitaxy) with two processes of process I ($850^{\circ}C$-12 minutes + $1080^{\circ}C$-30 minutes) and process II ($557^{\circ}C$-5 minutes + $900^{\circ}C$-5 minutes) on $CoSi_2$/Si substrates. An optical microscopy, FE-SEM, AFM, and HR-XRD (high resolution X-ray diffractometer) were employed to determine the GaN epitaxy. In case of process I, it showed no GaN epitaxial growth. However, in process II, it showed that GaN epitaxial growth occurred. Especially, in process II, GaN layer showed selfaligned substrate separation from silicon substrate. Through XRD ${\omega}$-scan of GaN <0002> direction, we confirmed that the combination of cobalt silicide and Si(100) as a buffer and HVPE at low temperature (process II) was helpful for GaN epitaxy growth.

• Journal of the Korean Ceramic Society
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• v.56 no.2
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• pp.178-183
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• 2019

A process of fabricating the foamed glass that has closed pores with 8 ~ 580 ㎛ sizes without a blowing agent by sintering 10 ㎛ boron-free glass powder composed of CaO, MgO, SO₃, Al₂O₃-83 wt% SiO₂ at a molding pressure of 0 ~ 120 MPa and a sintering temperature of 750 ~ 1000℃ was investigated. To analyze the glass transition temperature of glass powder, thermogravimetric analysis-differential thermal analysis (TGA-DTA) method were used. The microstructure and pore size of foamed glass were examined using the optical microscopy and field emission scanning electron microscopy (FE-SEM). For the thermal diffusivity and color of the fabricated samples, a heat flow meter and ultraviolet-visible-near-infrared (UV-VIS-NIR)-colormetry were used, respectively. In the TGA-DTA result, the glass transition temperature of glass powder was confirmed to be 626℃. In the microstructure result, closed pores of 7 ~ 20 ㎛ were formed at 750 ~ 900℃, and they were not affected by the molding pressure and sintering temperature. However, at 1,000℃, when there was 0 MPa molding pressure, closed pores of 580 ㎛ were confirmed, and the pore size decreased as the molding pressure increased. Moreover, at a molding pressure of 30 MPa or higher, closed pores of approximately 400 ㎛ were formed. The porosity showed an increasing trend of smaller molding pressure and larger sintering temperature, and it was controllable in the range of 5.69 ~ 68.45%. In the thermal diffusivity result, there was no change according to the molding pressure, and, by increasing the sintering temperature, up to 0.115 W/m·K could be obtained. The Lab color index (CIE-Lab) results all showed a similar translucent white color regardless of molding pressure and sintering temperature. Therefore, based on the foamed glass without boron and blowing agent, it was confirmed that white foamed glass, which has closed pores of 8 ~ 580 ㎛ and a thermal diffusivity characteristic of 0.115 W/m·K, can be fabricated by changing the molding pressure and sintering temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.1
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• pp.17-21
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• 2011

Copper (Cu) had been attractive material due to its superior properties comparing to other metals such as aluminum or tungsten and considered as the best metal which can replace them as an interconnect metal in integrated circuits. CMP (Chemical Mechanical Polishing) technology enabled the production of excellent local and global planarization of microelectronic materials, which allow high resolution of photolithography process. Cu CMP is a complex removal process performed by chemical reaction and mechanical abrasion, which can make defects of its own such as a scratch, particle and dishing. The abrasive particles remain on the Cu surface, and become contaminations to make device yield and performance deteriorate. To remove the particle, buffing cleaning method used in post-CMP cleaning and buffing is the one of the most effective physical cleaning process. AE(Acoustic Emission) sensor was used to detect dynamic friction during the buffing process. When polishing is started, the sensor starts to be loaded and produces an electrical charge that is directly proportional to the applied force. Cleaning efficiency of Cu surface were measured by FE-SEM and AFM during the buffing process. The experimental result showed that particles removed with buffing process, it is possible to detect the particle removal efficiency through obtained signal by the AE sensor.

• Journal of the Korean Electrochemical Society
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• v.11 no.4
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• pp.284-288
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• 2008

Sn-thin film as high capacitive anode for thin film lithium-ion battery was prepared by organic-electrolyte electroplating using Sn(II) acetate. Electrolytic solution including $Li^+$ and $Sn^{2+}$ had 3 reduction peaks at cyclic voltammogram. Current peak at $2.0{\sim}2.5\;V$ region correspond to the electroplating of Sn on Ni substrate. This potential value is lower than 2.91 V vs. $Li^+/Li^{\circ}$, of the standard reduction potential of $Sn^{2+}$ under aqueous media. It is the result of high overpotential caused by high resistive organic electrolytic solution and low $Sn^{2+}$ concentration. Physical and electrochemical properties were evaluated using by XRD, FE-SEM, cyclic voltammogram and galvanostatic charge-discharge test. Crystallinity of electroplated Sn-anode on a Ni substrate could be increased through heat treatment at $150^{\circ}C$ for 2 h. Cyclic voltammogram shows reversible electrochemical reaction of reduction(alloying) and oxidation(de-alloying) at 0.25 V and 0.75 V, respectively. Thickness of Sn-thin film, which was calculated based on electrochemical capacity, was $7.35{\mu}m$. And reversible capacity of this cell was $400{\mu}Ah/cm^2$.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.1 s.38
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• pp.1-5
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• 2006

We prepared 80 nm-thick TiSix on each 70 nm-thick amorphous silicon and polysilicon substrate using an RF sputtering with $TiSi_2$ target. TiSix composite silicide layers were stabilized by rapid thermal annealing(RTA) of $800^{\circ}C$ for 20 seconds. Line width of $0.5{\mu}m$ patterns were embodied by photolithography and dry etching process, then each additional annealing process at $750^{\circ}C\;and\;850^{\circ}C$ for 3 hours was executed. We investigated the change of sheet resistance with a four-point probe, and cross sectional microstructure with a field emission scanning electron microscope(FE-SEM) and transmission electron microscope(TEM), respectively. We observe an abrupt change of resistivity and voids at the silicide surface due to interdiffusion of silicide and composite titanium silicide in the amorphous substrates with additional $850^{\circ}C$ annealing. Our result implies that the electrical resistance of composite titanium silicide may be tunned by employing appropriate substrates and annealing condition.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.3
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• pp.101-105
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• 2006

We fabricated the nano $TiN_x$ by making of reaction between titanium powder and $Si_3N_4$ during planetary milling. The $TiN_x$ powder was sintered by spark plasma sintering machine after mixing with 50 wt% of titanium powder, and the sintered body was heat-treated at $850^{\circ}C$ in order to investigate its hardness property at the elevated temperature. We analyzed crystal structure by XRD. We observed the peaks of $TiN_{0.26}$ and TiN after 10 hours milling, and we observed TiN peak mainly after 20 hours milling. The reacted particle size distribution was investigated by FE-SEM. Increase of milling time, the size of reacted particles was decreased and the $10{\sim}20nm$ size of $TiN_x$ on the surface of titanium and $TiN_x$ was observed after 20 hours milling. The micro-Vickers hardness of mixed sintered body was about $1050kgf/mm^2$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.6
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• pp.313-318
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• 2017

The microstructure of a cobalt-base superalloy (ECY768) obtained by an investment casting process was studied. This work focuses on the resulting microstructures arising from different melt and mold temperatures in normal industrial environmental conditions. The characterization of the samples was carried out using optical microscopy, field emission scanning electron microscopy and energy-dispersive spectroscopy. In this study, the as-cast microstructure is an ${\alpha}-Co$ (face-centered cubic) dendritic matrix with the presence of a secondary phase, such as $M_{23}C_6-type$ carbides precipitated at grain boundaries. These precipitates are the main strengthening mechanism in this type of alloy. Other minority phases, such as the MC-type phase, was also detected and their presence could be linked to the manufacturing process and environment.