• Journal of the Korean Vacuum Society
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• v.21 no.5
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• pp.233-241
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• 2012

We have deposited the bilayer consisted of the underlayer and the overlayer by using DC magnetron sputter on Single crystal MgO (001) substrate. This bilayer was fabricated at fixed annealing temperature and time. We have controlled agglomeration effect by changing of the bilayer thickness. Finally, we have made the self-organization and nano-structured film. In this processing, we have made nano-dot which consists of the underlayer and the overlayer, unlike the existing method called the agglomeration effect in the single layer. The underlayer has deposited using Ti, Cr and Co. And the overlayer has deposited with Ag. Through the analysis of Atomic force microscopy (AFM), the microstructure of underlayer is observed by AFM to confirm the formation of nano-dot. As the nano-dot through above processing, we have found that the nano-dot has the different shape. As a result, when we manufactured nano-dot through the agglomeration effect of bi-layer, the best matching material is Ti for underlayer. And also, we have found that MgO/Ti/Ag samples have been grown expitaxially toward the direction of MgO (001) by X-ray Diffraction analysis.

• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.618-624
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• 2013

We demonstrated unique inter- and intra-plasmonic coupling effects in bimetallic Au@Ag core-shell NP arrays which are regularly or randomly arranged on self-assembled block copolymer (BCP) inverse micelle monolayers. Polyvinylpyrrolidone (PVP)-stabilized Au@Ag core-shell NP arrays in regular or disordered configuration were incorporated and assembled on reconstructed PS-b-P4VP inverse micelle templates through two types of processes. The intensively enhanced LSPR coupling properties of individual and assembled Au@Ag NPs were evaluated by UV-visible spectroscopy in terms of the type of ligand stabilizer, coupling between Au and Ag, thickness of Ag shell, and type of array configuration. Finally, Au@Ag core-shell NP arrays were employed as active substrates for surface enhanced Raman spectroscopy (SERS) and a significantly enhanced signal enhancement was observed in accordance with the coupling intensity of Au@Ag NPs patterns.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.8
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• pp.531-536
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• 2017

Nano/micro technology is currently applied to improve solid surface wettability, with recent research studies indicating that nanostructures can improve surface wettability in the hydrophilic direction, and liquid spreading (propagation) is generated by capillary wicking. The majority of the existing research involves qualitative analysis of the spreading phenomena, owing to the difficulty in conducting small-scale analysis (nanostructures). In this study, the droplet interfacial behavior on silicon surfaces with micro/nano/micro-nano structures is experimentally investigated. The interfacial behavior is directly visualized using synchrotron X-ray imaging (side view). The spreading phenomena occur on structured surfaces, and the liquid interface behaviors on the surfaces differ. The liquid film thickness is uniform during spreading on the microstructured surface, but not on the nano case which shows a gentle slope. These combined spreading shapes were observed on a micro-nano structured surface, and liquid propagation was enhanced when the micro- and nano-structures are combined.

• Tribology and Lubricants
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• v.32 no.3
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• pp.75-81
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• 2016

Future electronics such as electronic paper and foldable cellphone are required to be flexible and transparent and should have a high performance. In order to fabricate the flexible electronics using flexibility transfer process, techniques for transferring various devices from rigid substrate onto flexible substrate by elastomeric stamp, have been developed. Adhesion between the elastomeric stamp and various devices is crucial for successful transfer process. The adhesion can be controlled by the thickness of the stamp, separation velocity, contact load, and stamp surface treatment. In this study, we fabricated the bump shape stamp consisting of a UV-curable polymer and investigated the effects of curing condition, separation velocity, and contact load on the adhesion characteristics of bumps. The bumps with hemispherical shape were fabricated using a dispensing process, which is one of the ink-jet printing techniques. Curing conditions of the bumps were controlled by the amount of UV irradiation energy. The adhesion characteristics of bumps are evaluated by adhesion test. The results show that the pull-off forces of bumps were increased and decreased as UV irradiation energy increased. For UV irradiation energies of 300 and 500 mJ/cm², the pull-off forces were increased as the separation velocity increased. The pull-off forces also increased with the increase of contact load. In the case of UV irradiation energy above 600 mJ/cm², however, the pull-off forces were not changed. Therefore, we believe that the bump shape stamp can be applied to roll-based transfer process and selective transfer process as an elastomeric stamp.

• Composites Research
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• v.19 no.5
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• pp.28-33
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• 2006

In this paper, we have studied the complex permittivities and their influence on the design of microwave absorbers of E-glass fabric/epoxy composite laminates containing three different types of carbon-based nano conductive fillers such as carbon black (CB), carbon nano fiber (CNF) and multi-wall nano tube (MWNT). The measurements were performed fur permittivities at the frequency band of 0.5 GHz$\sim$18.0 GHz using a vector network analyzer with a 7 mm coaxial air line. The experimental results show that the complex permittivities of the composites depend strongly on the natures and concentrations of the conductive fillers. The real and imaginary parts of the complex permittivities of the composites were proportional to the filler concentrations. But, depending on the types of fillers and frequency band, the increasing rates of the real and imaginary parts with respect to the filler concentrations were all different. These different rates can have an effect on the thickness in designing the single layer microwave absorbers. The effect of the different rates at 10 GHz was examined by using Cole-Cole plot; the plot is composed of a single layer absorber solution line and measured permittivities from these three types of composites. Single layer absorbers of 3 different thicknesses using carbon nano materials were fabricated and the -10 dB band of absorbing performances were all about 3 GHz.

• Journal of the Korean Magnetics Society
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• v.22 no.1
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• pp.6-10
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• 2012

We have observed the change in the film resistance of thin nickel film up to 13 nm, which is deposited on a porous anodic alumina substrate, prepared by two-step anodization technique under phosphoric acid. The resulting film grows as a porous film, following the pore structure on the surface of the alumina substrate, and the value of the resistance lies above $150k{\Omega}$ within the range of thickness studied here, decreasing very slowly with the film thickness. The observed resistance value is much higher than the reported value of a uniform film at the same thickness. Since the observed value of the surface coverage with the pores is smaller than the critical value, expected from the percolation theory, the pore structure limits the formation of conduction channel across the film. In addition, by comparing to the typical model of thickness-dependent resistivity, we expect that the scattering at the pore edge further increases the film resistance.

• Journal of the Korean Magnetics Society
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• v.8 no.3
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• pp.131-137
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• 1998

The thickness dependence of the microstructure and the giant magnetoresistance behavior of co-evaporated Co-Ag granular alloy films were investigated. The maximum magnetoresistance ratio of 24% was observed in the the as-deposited state of the 40 at. % Co alloy having 200 nm thickness. The surface scattering contributed about 20% to the total resistivity in the 20 nm thick films. The MR ratio dropped sharply when the film thickness was below 50 nm. The reduction in the Co particle size and the increase in solid solubility of Ag in fcc Co when the film thickness decreased were observed using a high resolution TEM. The aspect ratio of the Co particles was also affected by the film thickness. Those microstructural changes as well as the surface induced spin flipping play a significant role in the $\Delta$p change.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.907-909
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• 2009

In this paper, the dependence of threshold voltage on the gate oxide thickness, which it mostly influenced on short channel effects in fabrication of FinFET, has been investigated. The transport model based on three dimensional Possion's equation has been used to analyze influence on gate oxide thickness. The gate oxide thickness is the most important factor to influence on the threshold voltage in nano structure FinFET. The potential distributions of this model are compared with those of three dimensional numerical simulation to verify this model. As a result, since potential model presented in this paper is good agreement with hree dimensional numerical model, the threshold voltage characteristics have been considered according to the gate oxide thickness of FinFET.

• Journal of Korean Ophthalmic Optics Society
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• v.14 no.1
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• pp.57-62
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• 2009

Purpose: TiN films were deposited on sus304 by unbalanced magnetron sputtering system which was designed and developed as unbalancing the strength of the magnets in the magnetron electrode. The color and hardness of deposited TiN films was investigated. Methods: The cross sections of deposited films on silicon wafer were observed by SEM to measure the thickness of the films, the components of the surface of the films were identified by XPS, the components of the inner parts of the films were observed by XPS depth profiling. XPS high resolution scans and curve fittings of deposited films were performed for quantitative chemical analysis, Vickers micro hardness measurements of deposited films were performed with a nano indenter equipment. Results: The colors of deposited films gradually changed from light gold to dark gold, light violet, and indigo color with increasing of the thickness. It could be seen that the color change come from the composite change of three compound,$TiO_{x}N_{y}$, $TiO_2$, TiN. Especially, the composite change of$TiO_{x}N_{y}$ compound was thought to affect the color change with respect to thickness. Conclusions: Deposited films had lower than the value of general TiN film in Vickers hardness, which was caused by mixing three TiN, $TiO_2$,$TiO_{x}N_{y}$ compound in the deposited films. The increasing and decreasing of micro hardness with respect to thickness was thought to have something to do with the composite of TiN in the films.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.231-231
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• 2012

Correct determination of the interface locations is critical for the calibration of the depth scale and measurement of layer thickness in SIMS depth profiling analysis of multilayer films. However, the interface locations are difficult to determine due to the unwanted distortion from the real ones by the several effects due to sputtering with energetic ions. In this study, the layer thicknesses of Si/Ge and Si/Ti multilayer films were measured by SIMS depth profiling analysis using the oxygen and cesium primary ion beam. The interface locations in the multilayer films could be determined by two methods. The interfaces can be determined by the 50 at% definition where the atomic fractions of the constituent layer elements drop or rise to 50 at% at the interfaces. In this method, the raw depth profiles were converted to compositional depth profiles through the two-step conversion process using the alloy reference relative sensitivity factors (AR-RSF) determined by the alloy reference films with well-known compositions determined by Rutherford backscattering spectroscopy (RBS). The interface locations of the Si/Ge and Si/Ti multilayer films were also determined from the intensities of the interfacial composited ions (SiGe+, SiTi+). The determination of the interface locations from the composited ions was found to be difficult to apply due to the small intensity and the unclear variation at the interfaces.