• Korean Journal of Materials Research
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• v.24 no.9
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• pp.443-450
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• 2014

Amorphous (a-Si) films were epitaxially crystallized on a very thin large-grained poly-Si seed layer by a silicide-enhanced rapid thermal annealing (SERTA) process. The poly-Si seed layer contained a small amount of nickel silicide which can enhance crystallization of the upper layer of the a-Si film at lower temperature. A 5-nm thick poly-Si seed layer was then prepared by the crystallization of an a-Si film using the vapor-induced crystallization process in a $NiCl_2$ environment. After removing surface oxide on the seed layer, a 45-nm thick a-Si film was deposited on the poly-Si seed layer by hot-wire chemical vapor deposition at $200^{\circ}C$. The epitaxial crystallization of the top a-Si layer was performed by the rapid thermal annealing (RTA) process at $730^{\circ}C$ for 5 min in Ar as an ambient atmosphere. Considering the needle-like grains as well as the crystallization temperature of the top layer as produced by the SERTA process, it was thought that the top a-Si layer was epitaxially crystallized with the help of $NiSi_2$ precipitates that originated from the poly-Si seed layer. The crystallinity of the SERTA processed poly-Si thin films was better than the other crystallization process, due to the high-temperature RTA process. The Ni concentration in the poly-Si film fabricated by the SERTA process was reduced to $1{\times}10^{18}cm^{-3}$. The maximum field-effect mobility and substrate swing of the p-channel poly-Si thin-film transistors (TFTs) using the poly-Si film prepared by the SERTA process were $85cm^2/V{\cdot}s$ and 1.23 V/decade at $V_{ds}=-3V$, respectively. The off current was little increased under reverse bias from $1.0{\times}10^{-11}$ A. Our results showed that the SERTA process is a promising technology for high quality poly-Si film, which enables the fabrication of high mobility TFTs. In addition, it is expected that poly-Si TFTs with low leakage current can be fabricated with more precise experiments.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.634-634
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• 2013

Transfer molding methods have a problem that weak adhesion between nanostructures and substrates. It is important to make various nano scale applications, also the stability of nanostructure on substrate is related with device performance. We studied an effect of poly 4-vinylphenol (PVP) as the polymeric adhesion layer between organic nanowires and a Si substrate when the nanowires are transferred by liquid-bridge-mediated nanotransfer molding method (LB-nTM). Their structural stability was examined by optical microscopy, scanning electron microscopy as multiple transfer molding and washing process. Field-effect transistors were fabricated with organic semiconductor nanowires on a polymeric adhesion layer and their electrical properties showed no significant difference as the one without the adhesion layer. As a result, adhesion layer can be used in the washing process and making multi-layer nano-scale patterns.

• Journal of Sensor Science and Technology
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• v.24 no.2
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• pp.83-87
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• 2015

In this paper, we fabricated a low-cost glucose sensor with a simpler structure and fabrication process than the existing glucose sensor. The currently used glucose sensor has a three-layer structure with upper, middle, and bottom plates; here, we fabricated a single-layer glucose sensor using only a printing and dispensing process. We successfully fabricated the glucose sensor using a simple method involving the formation of an electrode and insulator layer through a 2- or 3-step printing process on plastic or paper film, followed by the dispensing of glucose oxidase solution on the electrode. Cyclic voltammetry (CV) and cyclic amperometry (CA) measurements were used to evaluate the characteristics of the fabricated single-layer glucose sensor. Also, its sensitivity was analyzed through glucose-controlled blood measurements. Hence, a low-cost single-layer glucose sensor was fabricated with evaluation of its characteristics demonstrating that it has useful application in medicine.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.4
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• pp.97-103
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• 2012

This study investigates thermal insulation properties of multi layer materials depending on thickness of air layers. Numerical analysis on the heat flow of different insulating materials was conducted to identify whether their temperature distributions demonstrate the reduced rate of heat transfer conclusively or not. Analytical model is divided into two categories. One is to distinguish temperature distribution of the air-layer materials from the non-air layer ones. The other is to compare the efficacy between eight-layered insulating materials with no air-layer contained and three-layered insulating materials which include an air-layer definitely. In the latter case, the identical thickness is assigned to each material. The effect of thermal insulation by including an air-layer is verified in the first analytical model. The result of the second model shows that the insulation of the eight-layered materials is coterminous at the three-layered ones with an air-layer and the thermal insulation of the two materials is imperceptible. The benefits of cost and energy saving are anticipated if air-layers are efficiently incorporated in multi layer insulating materials in a greenhouse.

• Electrical & Electronic Materials
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• v.9 no.6
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• pp.600-604
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• 1996

High-T$_{c}$, superconducting wire is very important element for the application of electrical power systems. But it is very difficult to develope the long high T, wire with excellent properties. BiSrCaCuO multi-layer tapes are fabricated by a rolling method and pressing method sintered for several step at 840.deg. C. The critical current densities of 637 filament multi-layer tapes sintering 100 hours fabricated by the rolling method and pressing method are 1.3*10$^{4}$ A/cm$^{2}$ and 5.5*10$^{3}$ A/cm$^{2}$. The critical cur-rent densites of multi-layer tapes made by rolling method are found to be better than those fabricated by the powder-in-tube method and pressing process. As result, the rolling method is the best way to fabricated the multi-layer filament.t.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.316-316
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• 2014

Two different transparent conducting oxide (TCO) layers of Al-doped ZnO (AZO) and $WO_3$ were prepared by a rf sputtering process. Working pressure, deposition time, and target-to-substrate distance were varied for the sputtering process to improve electrical properties of the resulting layer. Thickness of the TCO layers was measured by a profile meter of ${\alpha}$-step. To evaluate the electrical conductivity, surface resistivity of the TCO layers was measured by a four-point probe technique. Decrease of the working pressure resulted in increase of deposition rate and decrease of surface resistivity of the resulting layer. Increase of the layer thickness due to increased deposition time resulted in decrease of surface resistivity of the resulting layer. The shorter the target-to-substrate distance was, the lower was the surface resistivity of the resulting layer.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.510-520
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• 2019

To investigate the morphology characteristics of air layer in the air cavity, a numerical method with the combination of RANS equations and VOF two-phase-flow model is proposed for a plate with air cavity. Based on the model above, the dynamic and developmental process of air layer in the air cavity is studied. Numerical results indicate that the air layer in the plate's air cavity exhibits the dynamic state of morphology and the wavelength of air layer becomes larger with the increasing speed. The morphology of air layer agrees with the Froude similarity law and the formation of the air layer is not affected by the parameters of the cavity, however, the wave pattern of the air layer is influenced by the parameters of the cavity. The stable air layer under the air cavity is important for the resistance reduction for the air layer drag reduction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.432-435
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• 1997

In AC PDP, electrodes are covered with dielectric layer and the discharge is formed on the surface of the dielectric layer. MgO protection layer on the dielectric layer in PDP prevents a dielectric layer from sputtering and lowers the firing voltage due to a large secondary electron emission yield( ${\gamma}$ ). Until now, the MgO protection layer is mainly prepared by E-beam evaporation. However, there are some problems that is easy pollution and change of its characteristics with time and delamination. Therefore, in this study, MgO protection layer is prepared on dielectric layer by reactive R.F. magnetron sputtering with MgO target. Discharge characteristics and secondary electron emission coefficients of PDP are studied as a parameter of preparation conditions. Discharge voltage characteristics of the prepared MgO layer can be stable and improved by the annealing process in vacuum chamber.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.75.2-75.2
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• 2010

We studied the fabrication of polycrystalline silicon (pc-Si) films as seed layers for application of pc-Si thin film solar cells, in which amorphous silicon (a-Si) films in a structure of glass/Al/$Al_2O_3$/a-Si are crystallized by the aluminum-induced layer exchange (ALILE) process. The properties of pc-Si films formed by the ALILE process are strongly determined by the oxide layer as well as the various process parameters like annealing temperature, time, etc. In this study, the effects of the oxide film thickness on the crystallization of a-Si in the ALILE process, where the thickness of $Al_2O_3$ layer was varied from 4 to 50 nm. For preparation of the experimental film structure, aluminum (~300 nm thickness) and a-Si (~300 nm thickness) layers were deposited using DC sputtering and PECVD method, respectively, and $Al_2O_3$ layer with the various thicknesses by RF sputtering. The crystallization of a-Si was then carried out by the thermal annealing process using a furnace with the in-situ microscope. The characteristics of the produced pc-Si films were analyzed by optical microscope (OM), scanning electron microscope (SEM), Raman spectrometer, and X-ray diffractometer (XRD). As results, the crystallinity was exponentially decayed with the increase of $Al_2O_3$ thickness and the grain size showed the similar tendency. The maximum pc-Si grain size fabricated by ALILE process was about $45{\mu}m$ at the $Al_2O_3$ layer thickness of 4 nm. The preferential crystal orientation was <111> and more dominant with the thinner $Al_2O_3$ layer. In summary, we obtained a pc-Si film not only with ${\sim}45{\mu}m$ grain size but also with the crystallinity of about 75% at 4 nm $Al_2O_3$ layer thickness by ALILE process with the structure of a glass/Al/$Al_2O_3$/a-Si.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.113-116
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• 2005

In this paper, a computational and experimental analysis about the flow behavior of thin polymer film in the spin coating process for stable cover layer coating of a blu-ray disc is described. The blu-ray disc, a next-generation optical disc format over 25GB, consists of a 1.1mm thick substrate and a 0.1mm tick cover layer. Generally, cover layer on the blu-ray disc is made by the polymer spin coating process. However, it is hard to secure sufficient coating uniformity around the rim on the cover layer. In order to get the uniform thickness deviation and to minimize the bead around the rim, the edge of the disc substrate can be modified into various shapes around the rim on the disc and analyzed with various parameters, such as surface tension, viscosity, and rotation speed, etc. The optimal shape of the rim was tried to get by 3 dimensional computer simulation of the polymer expulsion process.