• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04a
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• pp.23-26
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• 2004

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a Carbon Nitride (NDLC) thin film. NDLC thin film exhibits high electrical resistivity and thermal conductivity that are similar to the properties shown by diamond-like carbon (DLC) thin films. The diamond-like properties and nondiamond-like bonding make NDLC an attractive candidate for applications. A high pretilt angle of about $9.9^{\circ}$ by ion beam (IB) exposure on the NDLC thin film surface was measured. A good LC alignment is achieved by the IB alignment method on the NDLC thin film surface at annealing temperature of $200^{\circ}C$. The alignment defect of the NLC was observed above annealing temperature of $250^{\circ}C$. Consequently, the high pretilt angle and the good LC alignment by the IB alignment method on the NDLC thin film surface can be achieved.

• Transactions on Electrical and Electronic Materials
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• v.13 no.3
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• pp.111-115
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• 2012

Spray pyrolysis method was applied for the preparation of indium oxide ($In_2O_3$) thin films, by varying the substrate temperature range from 400-$600^{\circ}C$. All the samples were characterized at room temperature by using X-Ray diffraction, Scanning electron microscopy, Atomic Force Microscopy, Hall Effect and UV-Visible spectrophotometry. The optimal substrate temperature required for obtaining films of high crystallographic quality was $575^{\circ}C$. By comparing optical transmittance and electrical conductivity it was observed that the best figure of merit for these films was achieved for the same temperature and electrical resistivity was in the order of ${\rho}=1.47{\times}10^{-1}[{\Omega}cm]$. Gas sensing measurements of the films in ethanol showed enhancement with surface roughness and sheet resistance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.11
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• pp.977-980
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• 2008

We investigated the effects of power ratio on the electrical and optical properties of Au based Ga-, B- codoped ZnO(GZOB) thin films. GZOB thin films were deposited on Au based poly carbonate(PC) substrate with various power in the range from 60 to 120 W by DC magnetron sputtering. In the result, GZOB films at 100 W exhibited a low resistivity value of $1.12\times10^{-3}\Omega-cm$, and a visible transmission of 80 % with a thickness of 300 nm. This result indicated that the addition of Ga and B in ZnO films leads to the improvement of conductivity and transparent. From the result, we can confirm the possibility of the application as transparent conductive electrodes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.144-144
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• 2007

Effects of power ratio on the electrical and optical properties of Au based Ga-, B- codoped ZnO(GZOB) thin films were investigated. GZOB thin films on Au based PC flexible substrate were deposited at various power in the range from 50 to 125 W by DC magnetron sputtering. Au layer was fabricated to achieve good electrical conductivity. The presence of additional boron impurity leads to improve structural defects. Thus, the c-axis orientation along (002) plane was enhanced with the increasing of power ratio and the surface morphology of the films showed a homogeneous and nano-sized microstructure. GZOB films grown at 125W were investigated a low resistivity value of $1{\times}10^{-3}{\Omega}cm$ and a visible transmission of 80% with a thickness of 300nm.

• Transactions on Electrical and Electronic Materials
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• v.18 no.3
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• pp.151-154
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• 2017

In this article, we investigated the various influencing factors that degraded the lifetime of suspension insulators in 154 kV transmission lines, and showed the possible solutions to avoid such breakdowns. With respect to achieve safety, reliability and aesthetical considerations, the characteristics of transmission and distribution network power cables should be improved. Suspension insulators are particularly important to study, as they have developed to be the main component of transmission lines due to their ability to withstand the electrical conductivity of high-voltage power transmission. Suspension insulators are mostly made from glass, rubber and ceramic material due to their high resistivity. In Korea, porcelain suspension insulators are typically used in the transmission line system, as they are cheaper and more flexible compared to other types of insulators. This is effective from preventing very high and steep lightening impulse voltages from causing the breakdown of suspension insulators used in power lines. Other influential factors affect the lifetime of suspension insulators that we studied include temperature, water moisture, contamination, mechanical vibration and electrical stress.

• Journal of the Korean Institute of Gas
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• v.12 no.2
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• pp.32-37
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• 2008

For a development of U-safety system, liquid/gas-sensors that are easy to carry and install in any place are needed. Therefore, in this work, we prepared porous gold using a templating method with nanoporous alumina, and it was used as sensing materials and electrode. The resulting materials showed high purity macroporous structure with $200{\sim}300\;nm$ of window-pore and $4.8\;m^2/g$ of surface area. Because porous gold had good electric conductivity, convenience to measure the change of electric resistivity and good reproducibility, it could be used as potential sensing materials. As a proof-of-concept test, the detection test for mercury ion was carried out.

• Korean Journal of Materials Research
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• v.27 no.12
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• pp.695-698
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• 2017

ZnMgBeGaO/Ag/ZnMgBeGaO multilayer structures were sputter grown and characterized in detail. Results indicated that the electrical properties of the ZnMgBeGaO films were significantly improved by inserting an Ag layer with proper thickness (~ 10 nm). Structures with thicker Ag films showed much lower optical transmission, although the electrical conductivity was further improved. It was also observed that the electrical properties of the multilayer structure were sizably improved by annealing in vacuum (~35 % at $300^{\circ}C$). The optimum ZnMgBeGaO(20nm)/Ag(10nm)/ZnMgBeGaO(20nm) structure exhibited an electrical resistivity of ${\sim}2.6{\times}10^{-5}{\Omega}cm$ (after annealing), energy bandgap of ~3.75 eV, and optical transmittance of 65 % ~ 95 % over the visible wavelength range, representing a significant improvement in characteristics versus previously reported transparent conductive materials.

• Journal of Magnetics
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• v.10 no.3
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• pp.128-132
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• 2005

We report optical ab-plane properties of the layered sodium cobaltate, $Na_xCoO_2$ for x = 0.35 and 0.75. Two samples show metallic behaviors according to dc resistivity transport. Overall temperature dependent optical conductivities of both samples are very similar to those of the high temperature superconducting underdoped cuprates. We found that the optical scattering rate of x = 0.75 sample, which is in a Curie-Weiss metallic phase, varies linearly (non-Fermi liquid) with frequency and temperature while that of x = 0.35 sample, which is in a paramagnetic metallic phase, varies quadratically (Fermi liquid) with frequency and temperature. Both x = 0.35 and 0.75 samples have an onset of scattering around $600\;cm^{-1}$ which can be attributed to the interaction of charge carriers with a bosonic collective mode in a system.

• Journal of the Semiconductor & Display Technology
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• v.16 no.4
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• pp.75-78
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• 2017

The $CO_2$ gas responsibility of $SnO_2$ thin films was researched with various annealing temperatures. $SnO_2$ was prepared on n-type Si substrate by RF magnetron sputtering system and annealed in a vacuum condition. The bonding structure of $SnO_2$ was changed from amorphous to crystal structure with increasing the annealing temperature, and the content of oxygen vacancy was researched the highest of the annealed at $60^{\circ}C$. The $SnO_2$ annealed at $60^{\circ}C$ had the characteristics of the highest capacitance. The special properties of $CO_2$ gas responsibility was found at the $SnO_2$ thin film annealed at $60^{\circ}C$ with amorphous structure because of the combination with the oxygen vacancies and $CO_2$ gases changed the resistivity. The amorphous structure enhanced the responsibility at the $SnO_2$ surface and the conductivity of $SnO_2$ thin film.

• Korean Journal of Metals and Materials
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• v.48 no.2
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• pp.169-174
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• 2010

A micro gas sensor for formaldehyde (HCHO) gas was fabricated by using MEMS (Micro Electro Mechanical System) technology and the sol-gel process. The sensing materials of the $SnO_2$-ZnO system were synthesized by the sol-gel method. The crystal structure and thermal analysis of the $SnO_{2}$-ZnO were characterized by XRD and DSC-TGA. The fabricated gas sensors were tested at various gas concentrations (0.5~5.0 ppm) and different operation temperatures ($350{\sim}550^{\circ}C$). The $SnO_2$-10 mol%ZnO sensor showed the highest sensitivity ($R_s=0.24$) for 1.0 ppm-formaldehyde at $500^{\circ}C$ and response time (90% saturation time) was within 20 seconds.