• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.147-148
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• 2007

Dye-sensitized solar cell using conversion of solar energy to electrical energy appeared that which solves a environmental matter. The dye-sensitized solar cell uses nano-crystalline oxide semiconductor for absorbing dye. The $TiO_2$ is used most plentifully. The efficiency of the dye-sensitized solar cell changes consequently in the particle size, morphology, crystallization and surface state of the $TiO_2$. In this paper, we report The effect of titania$(TiO_2)$ thickness on the performance of dye-sensitized solar cells. Using doctor blade method, It produced the thickness of the $TiO_2$ with $7\;{\mu}m,\;10\;{\mu}m,\;13\;{\mu}m$. The efficiency was the best from $10{\mu}m$. It had relatively low efficiency on the thickness from $7\;{\mu}m\;to\;13\;{\mu}m$. The reason why it presents low efficiency on $7\;{\mu}m$ thickness is that excited electrons can not be delivered enough due to thin thickness of $7\;{\mu}m\;TiO_2$. And The reason why it presents low efficiency on $13\;{\mu}m$ thickness is that thick $13\;{\mu}m\;TiO_2$ can not penetrate the sunlight enough.

• Korean Journal of Materials Research
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• v.22 no.7
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• pp.335-341
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• 2012

Recently, the demand for the miniaturization of printed circuit boards has been increasing, as electronic devices have been sharply downsized. Conventional multi-layered PCBs are limited in terms their use with higher packaging densities. Therefore, a build-up process has been adopted as a new multi-layered PCB manufacturing process. In this process, via-holes are used to connect each conductive layer. After the connection of the interlayers created by electro copper plating, the via-holes are filled with a conductive paste. In this study, a desmear treatment, electroless plating and electroplating were carried out to investigate the optimum processing conditions for Cu via filling on a PCB. The desmear treatment involved swelling, etching, reduction, and an acid dip. A seed layer was formed on the via surface by electroless Cu plating. For Cu via filling, the electroplating of Cu from an acid sulfate bath containing typical additives such as PEG(polyethylene glycol), chloride ions, bis-(3-sodiumsulfopropyl disulfide) (SPS), and Janus Green B(JGB) was carried out. The desmear treatment clearly removes laser drilling residue and improves the surface roughness, which is necessary to ensure good adhesion of the Cu. A homogeneous and thick Cu seed layer was deposited on the samples after the desmear treatment. The 2,2'-Dipyridyl additive significantly improves the seed layer quality. SPS, PEG, and JGB additives are necessary to ensure defect-free bottom-up super filling.

• Journal of the Korean institute of surface engineering
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• v.47 no.6
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• pp.316-322
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• 2014

With increase in demand for higher operating temperatures of gas turbines, extensive research efforts have been carried out to enhance the performance of thermal barrier coatings (TBCs) in the field of coating processing as well as materials. In this study, thermal barrier coatings in lanthanum/gadolinium zirconate system, which is one of the most promising candidates for replacing yttira-stabilized zirconia (YSZ) in thermal barrier coating applications, are fabricated via suspension plasma spray. Dense, $300{\sim}400{\mu}m$ thick coatings of fluoritephase zirconate with modest amount of segmented microstructures are obtained by using suspension plasma spray with suspensions of planetary-milled mixture between lanthanum and/or gadolinium oxide and nano zirconia. These coatings exhibit thermal conductivities of 1.6 ~ 1.7 W/mK at $1000^{\circ}C$, which is relatively lower than that of YSZ.

• Korean Journal of Metals and Materials
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• v.46 no.3
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• pp.182-188
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• 2008

Carbon nanotubes(CNTs) have outstanding mechanical, thermal, and electrical properties. Thus, by placing nanotubes into appropriate matrix, it is postulated that the resulting composites will have enhanced properties. Cold spray can produce thick metal-based composite coatings with very high density, low oxygen content, and phase purity, which leads to excellent physical properties. In this study, we applied cold spray coating process for the consolidation of Cu/CNT composite powder. The precursor powder mixture, in which CNTs were filled into copper particles, was prepared to improve the distribution of the CNT in copper matrix. Pure copper coating was also conducted by cold spraying as a reference. Annealing heat treatment was applied to the coating to examine its effect on the properties of the composite coating. The hardness of Cu/CNT composite coating represented similar value to that of pure copper coating. It was importantly found that the electrical conductivity of the Cu/CNT composite coating significantly increased from 53% for the standard condition to almost 55% in the optimized condition, taking annealed ($500^{\circ}C/1hr$.) copper coating as a reference (100%). The thermal conductivity of Cu/CNT composite coating layer was higher than that of pure Cu coating. It was also found that the electrical and thermal conductivities of Cu/CNT composite could be improved through annealing heat treatment. The microstructural evolution of Cu/CNT coating was also investigated and related to the macroscopic properties.

• Advances in materials Research
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• v.12 no.3
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• pp.243-261
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• 2023

This study aims to analyze the mechanical buckling behavior of a single-walled carbon nanotube (SWCNT) integrated with a one-parameter elastic medium and modeled as a Kerr-type foundation under a longitudinal magnetic field. The structure is considered homogeneous and therefore modeled utilizing the nonlocal first shear deformation theory (NL-FSDT). This model targets thin and thick structures and considers the effect of the transverse shear deformation and small-scale effect. The Kerr model describes the elastic matrix, which takes into account the transverse shear strain and normal pressure. Using the nonlocal elastic theory and taking into account the Lorentz magnetic force acquired from Maxwell relations, the stability equation for buckling analysis of a simply supported SWCNT under a longitudinal magnetic field is obtained. Moreover, the mechanical buckling load behavior with respect to the impacts of the magnetic field and the elastic medium parameters considering the nonlocal parameter, the rotary inertia, and transverse shear deformation was examined and discussed. This study showed useful results that can be used for the design of nano-transistors that use the buckling properties of single-wall carbon nanotubes(CNTs) due to the creation of the magnetic field effect.

• Structural Engineering and Mechanics
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• v.89 no.6
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• pp.557-570
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• 2024

Due to interfacial ageing, chemical action and interfacial damage, the interface debonding may appear in the interfaces of composite laminates. Particularly, the laminates display a side-dependent effect at small scale. In this work, a three-dimensional (3D) and anisotropic thick nanoplate model is proposed to investigate the effects of imperfect interface and nonlocal parameter on the bending deformation, vibrational response and buckling stability of one-dimensional (1D) hexagonal quasicrystal (QC) layered nanoplates. By combining the linear spring model with the transferring matrix method, exact solutions of phonon and phason displacements, phonon and phason stresses of bending deformation, the natural frequencies of vibration and the critical buckling loads of 1D hexagonal QC layered nanoplates are derived with imperfect interfaces and nonlocal effects. Numerical examples are illustrated to demonstrate the effects of the imperfect interface parameter, aspect ratio, thickness, nonlocal parameter, and stacking sequence on the bending deformation, the vibrational response and the critical buckling load of 1D hexagonal QC layered nanoplate. The results indicate that both the interface debonding and nonlocal effect can reduce the stiffness and stability of layered nanoplates. Increasing thickness of QC coatings can enhance the stability of sandwich nanoplates with the perfect interfaces, while it can reduce first and then enhance the stability of sandwich nanoplates with the imperfect interfaces. The biaxial compression easily results in an instability of the QC layered nanoplates compared to uniaxial compression. QC material is suitable for surface layers in layered structures. The mechanical behavior of QC layered nanoplates can be optimized by imposing imperfect interfaces and controlling the stacking sequence artificially. The present solutions are helpful for the various numerical methods, thin nanoplate theories and the optimal design of QC nano-composites in engineering practice with interfacial debonding.

• Analytical Science and Technology
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• v.25 no.6
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• pp.476-482
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• 2012

Asian dust particles are known to have sizes ranging from a few nanometers up to about a few micrometers. The environmental and health effects depend on the size of the dust particles. The smaller, the farther they are transported, and the deeper they penetrate into the human respiratory system. Sedimentation field-flow fractionation (SdFFF) provides separation of nano to microparticles using a combination of centrifugal force and parabolic laminar flow in a channel. In this study, the steric mode of SdFFF (Sd/StFFF) was tested for size-based separation and characterization of Asian dust particles. Various SdFFF experimental parameters including flow rate, stop-flow time and field strength of the centrifugal field were optimized for the size analysis of Asian dust. The Sd/StFFF calibration curve showed a good linearity with $R^2$ value of 0.9983, and results showed an excellent capability of Sd/StFFF for a size-based separation of micron-sized particles.The optical microscopy (OM) was also used to study the size and the shape of the dust particles. The size distributions of the samples collected during a thick dust period were shifted towards larger sizes than those of the samples collected during thin dust periods. It was also observed that size distribution of the sample collected during dry period shifts further towards larger sizes than that of the samples collected during raining period, suggesting the sizes of the dust particle decrease during raining periods as the components adsorbed on the surface of the dust particles were removed by the rain water. Results show Sd/StFFFis a useful tool for size characterization of environmental particles such as the Asian dust.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.8
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• pp.664-669
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• 2012

Nano-structured one-dimensional $Na_2Ti_6O_{13}$ particles were synthesized by a molten salt process. Effects of processing parameters on the microstructure and band gap energy of the $Na_2Ti_6O_{13}$ powder were studied in this paper. For the synthesis of the $Na_2Ti_6O_{13}$ particles, two different raw materials of tubular shaped Na-titanate (Na-TiNT) and spherical shaped $TiO_2$ were utilized. Synthesizing with the raw material of Na-TiNT, around 70nm thick 1D-$Na_2Ti_6O_{13}$ with the bandgap energy of 3.5 eV was obtained at $810^{\circ}C$. Below $810^{\circ}C$ or without the presence of NaCl, 1D-$Na_2Ti_6O_{13}$ was in a relatively short in length and agglomerated state. With the processing temperature increased, the thickness of the 1D-$Na_2Ti_6O_{13}$ was also observed to be increased. On the other hand, when $TiO_2$ was employed as a raw material, the mixed amount of $Na_2CO_3$ played an important role in transforming the morphology and phase of the raw material, affecting the bandgap energy of the synthesized product. Specific surface area of the synthesized 1D-$Na_2Ti_6O_{13}$ was significantly affected by the raw and mixed materials as well as processing temperature. When Na-TiNT was processed at $810^{\circ}C$ with NaCl, the specific surface area of the 1D-$Na_2Ti_6O_{13}$ showed the best value of 30.63 $m^2/g$.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.134-134
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• 2011

High-k dielectric materials such as $HfO_2$, $ZrO_2$ and $Al_2O_3$ increase gate capacitance and reduce gate leakage current in MOSFET structures. This behavior suggests that high-k materials will be promise candidates to substitute as a tunnel barrier. Furthermore, stack structure of low-k and high-k tunnel barrier named variable oxide thickness (VARIOT) is more efficient.[1] In this study, we fabricated the $WSi_2$ nanocrystals nonvolatile memory device with $SiO_2/HfO_2/Al_2O_3$ tunnel layer. The $WSi_2$ nano-floating gate capacitors were fabricated on p-type Si (100) wafers. After wafer cleaning, the phosphorus in-situ doped poly-Si layer with a thickness of 100 nm was deposited on isolated active region to confine source and drain. Then, on the gate region defined by using reactive ion etching, the barrier engineered multi-stack tunnel layers of $SiO_2/HfO_2/Al_2O_3$ (2 nm/1 nm/3 nm) were deposited the gate region on Si substrate by using atomic layer deposition. To fabricate $WSi_2$ nanocrystals, the ultrathin $WSi_2$ film with a thickness of 3-4 nm was deposited on the multi-stack tunnel layer by using direct current magnetron sputtering system [2]. Subsequently, the first post annealing process was carried out at $900^{\circ}C$ for 1 min by using rapid thermal annealing system in nitrogen gas ambient. The 15-nm-thick $SiO_2$ control layer was deposited by using ultra-high vacuum magnetron sputtering. For $SiO_2$ layer density, the second post annealing process was carried out at $900^{\circ}C$ for 30 seconds by using rapid thermal annealing system in nitrogen gas ambient. The aluminum gate electrodes of 200-nm thickness were formed by thermal evaporation. The electrical properties of devices were measured by using a HP 4156A precision semiconductor parameter analyzer with HP 41501A pulse generator, an Agillent 81104A 80MHz pulse/pattern generator and an Agillent E5250A low leakage switch mainframe. We will discuss the electrical properties for application next generation non-volatile memory device.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.4
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• pp.27-36
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• 2006

We fabricated thermally evaporated 10 nm-Ni/(poly)Si, 10 nm-Ni/l nm-Ir/(poly)Si and 10 nm-Ni/l nm-Pt/(poly)Si films to investigate the thermal stability of nickel monosilicides at the elevated temperatures by rapid annealing them at the temperatures of $300{\sim}1200^{\circ}C$ for 40 seconds. Silicides of 50 nm-thick were formed on top of both the single crystal silicon actives and the polycrystalline silicon gates. A four-point tester was used to examine sheet resistance. A scanning electron microscope and field ion beam were employed for thickness and microstructure evolution characterization. An X-ray diffractometer and an Auger depth profiler were used for phase and composition analysis, respectively. Nickel silicides with platinum have no effect on widening the NiSi stabilization temperature region. Nickel silicides with iridium farmed on single crystal silicon showed a low resistance up to $1200^{\circ}C$ while the ones formed on polycrystalline silicon substrate showed low resistance up to $850^{\circ}C$. The grain boundary diffusion and agglomeration of silicides lowered the NiSi stable temperature with polycrystalline silicon substrates. Our result implies that our newly proposed Ir added NiSi process may widen the thermal process window for nano CMOS process.