• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1447-1449
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• 1998

The c-axis orientation plays a very important role in controlling the main parameters of the perpendicular magnetic recording media, such as perepndicular magnetic anisotropy field $H_{K{\bot}}$, the ratio of coercive force $H_{C{\bot}}/H_{C//}$, the recording density $D_{50}$, and the dispersion of the c-axis orientation $\Delta\theta_{50}$, which is quite important for the performance as perpendicular recording media, as well as the magnetic properties of the film. In this study, the essential process requirement for preparing the Co-Cr films with the superior c-axis orientation, the dependence of $\Delta\theta_{50}$ and the magnetic properties on the film thickness $\delta$, and the effect of underlayer on the dispersion of c-axis orientation have been investigated for both the FTS and DCM system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1766-1775
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• 2001

A theoretical analysis on the heat and mass transfer in an evaporative cooler is presented in this work. The evaporative cooler is modeled as a channel filled with porous media the interstitial surface of which is covered by thin water film. Assuming that the Lewis number is unity and the water vapor saturation curve is linear, exact solutions to the energy and vapor concentration equations are obtained. Based on the exact solutions, the characteristics of the heat and mass transfer in the evaporative cooler are investigated. The comparison of the cooling performance between the evaporative cooler and the usual sensible heat exchanger is also carried out. Obviously, the evaporative heat exchanger shows better cooling performance than the sensible heat exchanger. This is due to the latent heat of water vaporization, which results in apparent increases both in the interstitial heat transfer coefficient and the specific heat of the air stream in the evaporative cooler.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.124-127
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• 2005

Rewritable optical memory devices such as an CD-RW and DVD+RW are data storage media, which take advantage of the different optical properties in the amorphous and crystalline states of phase change materials. The switching property, structural transformation, transformation kinetics and chemical bindings of $Ge_xSb_{100-x}$($6{\le}x{\le}$34) were studied to investigate the feasibility of applying $Ge_xSb_{100-x}$ alloys in optical memory. The $Ge_xSb_{100-x}$ thin film was deposited by RF magnetron co-sputtering system and phase change characteristics were investigated by X-ray diffraction (XRD), static tester, inductively coupled plasma atomic emission spectrometer (ICP-AES) and atomic force microscopy (AEM). Optimum fiim composition of $Ge_xSb_{100-x}$ was studied and its minimum time fur laser induced crystallization and optical contrast fur phase transition was performed. These results might be correlated with the binding energies between Ge and Sb, and indicate that $Ge_xSb_{100-x}$ have an potential far optical memory applications.

• Journal of the Korean Magnetics Society
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• v.5 no.2
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• pp.134-139
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• 1995

We produced $(Co_{93}Cr_{7})-P-Ni$ thin films for longitudinal magnetic recording media using OC magnetron sputtering system The variation of magnetic properties of $(Co_{93}Cr_{7})-P-Ni$ pseudo-ternary system with the composition was examined. We obtained the coercivity up to 1500 Oe. The coercivity iocrease could be ascribed to in-plane anisotropy enhaocement, grain size decrease, magnetic decoupling between particles. TEM micrographs showed that the grains were well-decoupled by the addition of phosphorous.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.889-892
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• 2009

We have developed a practical printing technology for the gate electrode of organic thin film transistors(OTFTs) by combining screen-printing with wet-etching process using nano-silver ink as a conducting material. The screen-printed and wet-etched Ag electrode exhibited a minimum line width of ~5 um, the thickness of ~65 nm, and a resistivity of ${\sim}10^{-6}{\Omega}{\cdot}cm$, producing good geometrical and electrical characteristics for gate electrode. The OTFTs with the screen-printed and wet-etched Ag electrode produced the saturation mobility of $0.13cm^2$/Vs and current on/off ratio of $1.79{\times}10^6$, being comparable to those of OTFT with the thermally evaporated Al gate electrode.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.247-250
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• 2007

Flexible media such as the paper, the film, etc. are thin, light and very flexible. They behave in geometrically nonlinear. Any of small force makes large deformation. So we must including aerodynamic effect when its behavior is predicted. Thus, it becomes fully coupled fluid-structure interaction(FSI) problem. In FSI problems, where the fluid mesh near the structure undergoes large deformations and becomes unacceptably distorted, which drive the time step to a very small value for explicit calculations, the arbitrary Lagrangian-Eulerian(ALE) methods or rezoning are used to create a new undistorted mesh for the fluid domain, which allows the calculations to continue. In this paper, FE sheet model considering geometric nonlinearity is formulated to simulate the behavior of the flexible media. Aerodynamic force to the media by surrounding air is calculated by solving the incompressible Navier-Stokes equations. Q2Q1(Taylor-Hood) element which means biquadratic for velocity and bilinear for pressure is used for fluid domain. Q2Q1 element satisfies LBB condition and any stabilization technique is not needed. In this paper, cantilevered sheet in the viscous incompressible Navier-Stokes flow is simulated to check the mesh motion and numerical integration scheme, and then falling paper in the air is simulated and the effects of some representative parameters are investigated.

• Journal of the Korean Magnetics Society
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• v.11 no.4
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• pp.168-172
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• 2001

Co-Zn ferrite thin films grown on thermally oxidized silicon wafers were fabricated by a sol-gel method. Magnetic and structural properties of Co-Zn thin films were investigated by using x-ray diffractometer (XRD), atomic force microscopy (AFM), auger electron spectroscopy (AES) and a vibrating sample magnetometer (VSM). Co-Zn ferrite thin films annealed at 400 $^{\circ}C$ presented have only a single phase spinel structure without any preferred crystallite orientation. Their surface roughness of Co-Zn ferrite thin films was shown as less than 3 nm and the grain size was about 40 nm for annealing temperatures over 600 $^{\circ}C$. A moderate saturation magnetization of Co-Zn ferrite thin films for recording media was obtained in this study and there is no significant difference of their magnetic property with those external fields of parallel and perpendicular to planes of the films. The maximum value of the coercivity was obtained as 1,900 Oe for Co-Zn ferrite thin film annealed at 600 $^{\circ}C$.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.173-179
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• 2006

We have investigated structural and electrical properties of $PbZr_{0.3}Ti_{0.7}O_{3}$ (PZT) thin films deposited by pulsed laser deposition methods. PZT thin films have been deposited on $LaMnO_3$ (LMO) bottom electrodes with $LaAlO_3$ (LAO) substrates during different deposition times. High-resolution x-ray diffraction data have shown that all the PZT films and bottom electrodes are highly oriented. The thickness of each film is determined by field-emission scanning electron microscope. We have also observed root mean square roughness by using atomic force microscopy mode, and local polarization distribution and retention behavior of a ferroelectric domain by using piezoelectric force microscopy mode. A PZT/LMO structure has shown good ferroelectric and retention properties as the media for nano-storage devices.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.421-427
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• 2009

We successfully fabricated 4.7-inch organic thin film transistors array with $640{\times}480$ pixels on flexible substrate. All the processes were done by photolithography, spin coating and ink-jet printing. The OTFT-Electrophoretic (EP) pixel structure, based on a top gate OTFT, was fabricated. The mobility, ON/OFF ratio, subthreshold swing and threshold voltage of OTFT on flexible substrate are: 0.01 ^2/V-s, 1.3 V/dec, 10E5 and -3.5 V. After laminated the EP media on OTFT array, a panel of 4.7-inch $640{\times}480$ OTFT-EPD was fabricated. All of process temperature in OTFT-EPD is lower than $150^{\circ}C$. The pixel size in our panel is $150{\mu}m{\times}150{\mu}m$, and the aperture ratio is 50 %. The OTFT channel length and width is 20 um and 200um, respectively. We also used OTFT to drive EP media successfully. The operation voltages that are used on the gate bias are -30 V during the row data selection and the gate bias are 0 V during the row data hold time. The data voltages that are used on the source bias are -20 V, 0 V, and 20 V during display media operation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.52-59
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• 2006

To construct its complex permittivity from the reflection coefficient of a thin film such as PCB substrate measured by open-ended coaxial probe, an integral equation is formulated using modal analysis and equivalent source. The accuracy of the conversion model based on the integral equation is confirmed in both cases of converted complex permittivities calculated from numerically computed and actually measured reflection coefficients. And the maximum valid frequency of open-ended coaxial probe is limited by the size of its flange.