• 한국전기전자재료학회논문지
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• 제21권9호
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• pp.848-852
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• 2008

Characteristics of microcrystalline-silicon thin-films deposited by plasma-enhanced chemical-vapor deposition (PECVD) method were studied. There were optimum values of RF power density and $H_2$ dilution ratio $(H_2/(SiH_4+H_2))$; maximum grain size of about 35 nm was obtained at substrate temperature of 250 $^{\circ}C$ with RF power density of 1.1 W/$cm^2$ and $H_2$ dilution ratio of 0.91. Larger grain was obtained with higher substrate temperature up to 350 $^{\circ}C$. Grain size dependence on RF power density and $H_2$ dilution ratio could be explained by etching effects of hydrogen ions and changes of species of reactive precursors on growing surface. Surface-mobility activation of reactive precursors by temperature could be a reason of grain-size dependence on the substrate temperature. Microcrystalline-silicon thin-films that could be used for flat-panel electronics such as active-matrix organic-light-emitting-diodes are expected to be fabricated successfully using these results.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.424-425
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• 2007

We have studied the optically compensated splay mode using reactive mesogen (RM) monomer to reduce setting voltage and phase transition time from initial bend to splay state. When the OCS cell has low pretilt angle close to $45^{\circ}C$, OCS state can be formed easily. The low pretilt angle was formed through the polymerization of UV curable reactive RM monomer at the surfaces. In this way, reorientation of the LC is well defined and thus the device shows better performances in setting voltage and phase transition time.

• Biomolecules & Therapeutics
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• 제22권6호
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• pp.477-490
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• 2014

Non-thermal atmospheric-pressure plasma, also named cold plasma, is defined as a partly ionized gas. Therefore, it cannot be equated with plasma from blood; it is not biological in nature. Non-thermal atmospheric-pressure plasma is a new innovative approach in medicine not only for the treatment of wounds, but with a wide-range of other applications, as e.g. topical treatment of other skin diseases with microbial involvement or treatment of cancer diseases. This review emphasizes plasma effects on wound healing. Non-thermal atmospheric-pressure plasma can support wound healing by its antiseptic effects, by stimulation of proliferation and migration of wound relating skin cells, by activation or inhibition of integrin receptors on the cell surface or by its pro-angiogenic effect. We summarize the effects of plasma on eukaryotic cells, especially on keratinocytes in terms of viability, proliferation, DNA, adhesion molecules and angiogenesis together with the role of reactive oxygen species and other components of plasma. The outcome of first clinical trials regarding wound healing is pointed out.

• 한국표면공학회지
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• 제31권3호
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• pp.171-176
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• 1998

Transparent conducting ITO (Indium Tin Oxide) thin films were prepared on soda lime glass by reactive dc magnetron sputtering mothod. The maaterial properties were measured by the X-ray diffraction meter (XRD) and atomic force microscopy (AFM) scanning. As a resuIts, the (400) park for $O_2 gas rate 2% grows uniquely as the preferred orientaon. However, the (400) peak exists at $O_2 gas rate 5% as well as the (222) peak appears abruptly as the main orietation. Both <100> and <111> grain alignments are consisted simultaneously in the XRE pattern of ITO thin films. The electrical charcteristics were esimated by the electrical resistivity, optical transmission, and Hall mobillty, ect. The resistivity of ITO thin film deposited at 4cm from the substrate center is increased from $2\times10^-4$ to $8\times10^-4\Omega$cm as a function of $O_2$ gas pressure (0~5%). The optical transmission curves with a rising of $O_2$ gas rate become shifted into longer wavelength range.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2018년도 춘계학술대회 논문집
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• pp.129-129
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• 2018

Hard coating application is effective way of cutting tool for hard-to-machine materials such as Inconel, Ti and composite materials focused on high-tech industries which are widely employed in aerospace, automobile and the medical device industry also Information Technology. In cutting tool for hard-to-machine materials, high hardness is one of necessary condition along with high temperature stability and wear resistance. In recent years, high-entropy alloys (HEAs) which consist of five or more principal elements having an equi-atomic percentage were reported by Yeh. The main features of novel HEAs reveal thermodynamically stable, high strength, corrosion resistance and wear resistance by four characteristic features called high entropy, sluggish diffusion, several-lattice distortion and cocktail effect. It can be possible to significantly extend the field of application such as cutting tool for difficult-to-machine materials in extreme conditions. Base on this understanding, surface coatings using HEAs more recently have been developed with considerable interest due to their useful properties such as high hardness and phase transformation stability of high temperature. In present study, the nanocomposite coating layers with high hardness on WC substrate are investigated using high entropy alloy target made a powder metallurgy. Among the many surface coating methods, reactive magnetron sputtering is considered to be a proper process because of homogeneity of microstructure, improvement of productivity and simplicity of independent control for several critical deposition parameters. The N2 is applied to reactive gas to make nitride system with transition metals which is much harder than only alloy systems. The acceleration voltage from 100W to 300W is controlled by direct current power with various deposition times. The coating layers are systemically investigated by structural identification (XRD), evaluation of microstructure (FE-SEM, TEM) and mechanical properties (Nano-indenter).

• 한국표면공학회지
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• 제37권6호
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• pp.307-312
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• 2004

Extensive efforts have been made in an attempt to utilize photocatalytic properties of $TiO_2$ in visible range. $TiO_2$ and TiO-N thin films were made by the DC reactive magnetron sputtering method at $300^{\circ}C$. Various gases (Ar, $O_2$ and $N_2$) were used and Ti target was impressed by 0.6 kW-5.8 kW power range. The hysteresis phenomenon of the $TiO_2$ thin film as a function of the discharge voltage characteristic was observed to be higher as applied power increases. That of TiO-N thin film was occurred at the 5.8 kW power. The cross section and surface roughness of thin films were observed by FE-SEM and AFM. Average surface roughness of TiO-N thin film was observed as $15.9\AA$ and that of $TiO_2$ as $13.2\AA$. The crystal phases of both $TiO_2$ and TiO-N thin films were found to be anatase structure. The atomic $\beta$-N (396 eV peak in N 1s XPS) was shown in the rutile crystal of TiO-N and was considered acting as the origin of wavelength shift to the visible light.

• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2004년도 학술논문집
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• pp.32-42
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• 2004

Recently, plasma surface-cleaning or surface-etching techniques have been focused in respect of the decontamination of spent or used nuclear parts and equipment. In this study the removal rate of metallic cobalt surface is experimentally investigated via its surface etching rate with a $CF_4-o_2$mixed gas plasma. Experimental results reveal that a mixed etchant gas with about 80% $CF_4$-20% $O_2$ (molar) gives the highest reaction rate and the rate reaches 0.06 ${\mu}m$/min at $380^{\circ}C$ and ion-assisted etching dramatically enhances the surface reaction rate. With a negative 300 V DC bias voltage applied to the substrate, the surface reaction initiation temperature lowers and the rate increases about 20 times at $350^{\circ}C$ and up to 0.43 ${\mu}m$/min at $380^{\circ}C$, respectively. Surface morphology analysis confirms the etching rate measurements. Auger spectrum analysis clearly shows the adsorption of fluorine atoms on the reacted surface. From the current experimental findings and the results discussed in previous studies, mechanistic understanding of the surface reaction, fluorination and/or fluoro-carbonylation reaction, is provided.

• 한국광물학회지
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• 제26권2호
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• pp.101-110
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• 2013

나노크기 매킨나와이트(nanocrystalline mackinawite, FeS)는 높은 비표면적을 지닌 반응성 높은 광물로, 오염된 지하수나 토양의 복원을 위해 널리 사용된다. 또한 매킨나와이트는 혐기성 부식반응에 대해 열역학적으로 안정하고, 황산염 환원미생물의 대사에 의해 재생된다는 장점이 있다. 하지만 매킨나와이트 나노입자는 지하수 흐름에 의해 멀리 확산되거나 입자집적이 일어나 대수층 공극을 막는다. 따라서 현장복원을 위한 투과반응벽(permeable reactive barrier)의 설치를 위해서 나노크기 매킨나와이트에 대한 변형이 필요하다. 이를 위해 본 연구에서는 코팅법을 활용해 매킨나와이트 나노입자를 알루미나(alumina, $Al_2O_3$) 및 활성알루미나(activated alumina) 표면에 증착시켰다. 매킨나와이트의 코팅량은 pH에 따라 현저히 달랐으며, 두 종의 알루미나 모두 약 pH 6.9에서 최대 코팅이 관찰되었다. 이 pH에서 알루미나와 매킨나와이트는 반대의 표면전하(surface charge)를 띠어 두 광물 간 정전기적 인력이 발생하고, 이로 인해 효율적인 코팅이 일어났다. 이 pH에서 알루미나 및 활성 알루미나에 의한 코팅량은 각각 0.038 $mmol{\cdot}FeS/g$과 0.114 $mmol{\cdot}FeS/g$이었다. 혐기성 조건에서 코팅되지 않은 알루미나 및 활성 알루미나, 그리고 최적 pH에서 코팅된 알루미나 및 활성 알루미나를 사용해 아비산염(arsenite) 흡착실험을 수행했다. 코팅되지 않은 활성 알루미나는 코팅되지 않은 알루미나와 비교해 단위질량당 높은 아비산염의 제거를 보여주었으나, 매킨나와이트의 코팅에 의한 흡착량 증가를 보이지 않았다. 활성 알루미나는 높은 비표면적을 지니고 있어 반응성 높은 수산화작용기(hydroxyl functional group)가 다수 존재했고, 이로 인해 코팅된 매킨나와이트에 의한 아비산염의 제거가 중요하지 않았다. 반면 알루미나는 매킨나와이트 코팅에 의해 향상된 아비산염의 제거율을 보였는데, 이것은 알루미나에 존재한 수산화작용기가 아비산염과의 표면배위결합(surface complexation)에 소모되고, 코팅된 매킨나와이트에 의한 부가적인 흡착이 일어났기 때문이다. 코팅된 알루미나는 이전에 연구된 코팅된 실리카와 비교해보면 단위 비표면적당 매킨나와이트의 코팅량이 약 8배 높았으며, 더 높은 아비산염에 대한 흡착력을 보였다. 따라서 본 연구의 결과는 코팅된 알루미나는 투과반응벽의 설치에 적합한 물질이고, 특히 아비산염으로 오염된 지하수의 정화에 유용하게 적용될 수 있음을 지시하고 있다.

• Bulletin of the Korean Chemical Society
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• 제34권9호
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• pp.2725-2730
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• 2013

Single C-reactive protein (CRP) molecules, which are non-specific acute phase markers and products of the innate immune system, were quantitatively detected on a gold-nanopatterned biochip using evanescent field-enhanced fluorescence imaging. The $4{\times}5$ gold-nanopatterned biochip (spot diameter of 500 nm) was fabricated by electron beam nanolithography. Unlabeled CRP molecules in human serum were identified with single-molecule sandwich immunoassay by detecting secondary fluorescence generated by total internal reflection fluorescence (TIRF) microscopy. With decreased standard CRP concentrations, relative fluorescence intensities reduced in the range of 33.3 zM-800 pM. To enhance fluorescence intensities in TIRF images, the distance between biochip surface and CRP molecules was optimally adjusted by considering the quenching effect of gold and the evanescent field intensity. As a result, TIRF only detected one single-CRP molecule on the biochip the first time.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.293-294
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• 2009

We proposed a novel single gap transflective liquid crystal display (LCD) using liquid crystal with negative dielectric anisotropy. We designed cell structure driven by fringe electric field in the transmissive (T) part and vertical electric field in the reflective (R) part. In the device, high surface pretilt angle of the LC in the R-part is achieved through polymerization of an UV curable reactive mesogen (RM) monomer at surfaces. By optimizing the parameters, a newly developed transflective display has characteristics such as single gap and single gamma curve.