• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.93-98
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• 2005

Rewritable optical disk is one of the essential data storage media in these days, which takes advantage of the different optical properties in the amorphous and crystalline states of phase change materials. As well known, data transfer rate is one of the most important parameter of the phase change optical disks, which is mostly limited by the crystallization speed of recording media. Therefore, we doped Sn/Bi to $Ge_2Sb_2Te_5$ alloy in order to improve the crystallization speed and investigated the dependence of phase change characteristics on Sn/Bi doping concentration. The Sn/Bi doped $Ge_2Sb_2Te_5$ thin film was deposited by RF magnetron co-sputtering system and phase change characteristics were investigated by X-ray diffraction (XRD), static tester, UV-visible spectrophotometer, electron probe microanalysis (EPMA), inductively coupled plasma mass spectrometer (ICP-MS) and atomic force microscopy (AFM). Optimum doping concentration of Bi and Sn were 5${\~}$6 at.$\%$ and the minimum time for crystallization was below than 20 ns. This improvement is correlated with the simple crystalline structure of Sn/Bi doped $Ge_2Sb_2Te_5$ and the reduced activation barrier arising from Sn/Bi doping. The results indicate that Sn/Bi might play an important role in the transformation kinetics of phase change materials..

• Journal of the Korean Magnetics Society
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• v.3 no.3
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• pp.221-228
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• 1993

The general requirements of recording media include recording performance, environmental stability, runnability on the drive or deck, and manufacturability. CoCrMo thin films were prepared using RF sputtering system for a study on chemical stability. Surface degradation of the CoCrMo thin film was studied by SEM, XPS and AES. Surface degradation was found to be dependent of sputtering condition and Mo content. Addition of Mo to CoCr thin film improved dramatically its surface degradation resistance in dilute sulfuric acid, as indicated by active-passive transition appeared in electrochemical polarization curve. Futhermore, the passive current density was decreased with increasing Mo content. The reduction in a number density of corrosion sites by Mo addition vms observed, after accelerated corrosion test. AES survey indicated that corrosion occured on the site with Cr depletion and highly concentrated chloride ions.

• KSBB Journal
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• v.17 no.3
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• pp.235-240
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• 2002

The surface of polypropylene was modified by 1 keV $Ar^+$ ion beam in an $O_2$ environment in order to enhance wettability. Contact angle of deionized water on modified polypropylene was reduced from $78^{\circ}$to $22^{\circ}$. The enhanced wettability is originated from newly formed functional groups such as ether, carbonyl, and carbonyl groups. During immersion in deionized water, the enhanced wettability has remained nearly same. After washing in water, the hydrophilic functional groups on the polymer surface have been very stable. The modified polypropylene was adopted as bio-film media to remove organics in synthetic wastewater. Microbe adhesion on the polypropylene surface was improved due to the newly formed hydrophilic groups.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.2
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• pp.92-97
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• 2013

In this paper the author proposes a method of implementing a numerical model for threshold voltage ($V_{th}$) shift in organic thin-film transistors (OTFTs) into SPICE tools. $V_{th}$ shift is first numerically modeled by dividing the shift into sequentially ordered groups. The model is then used to derive a simulations model which takes into simulation parameters and calculation complexity. Finally, the numerical and simulation models are implemented in AIM-SPICE. The SPICE simulation results agree well with the $V_{th}$ shift obtained from an OTFT fabricated without any optimization. The proposed method is also used to implement the stretched-exponential time dependent $V_{th}$ shift in AIM-SPICE and the results show the proposed method is applicable to various types of $V_{th}$ shifts.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.5
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• pp.341-346
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• 2013

Threshold voltage shift caused by trapping and release of charge carriers in a thin-film transistor (TFT) is implemented in AIM-SPICE tool. Turning on and off voltages are alternatively applied to a TFT to extract charge trapping and releasing process. Each process is divided into sequentially ordered processes, which are numerically modeled and implemented in a computer language. The results show a good agreement with the experimental data, which are modeled. Since the proposed method is independent of TFT's behavior models implemented in SPICE tools, it can be easily added to them.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.550-552
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• 2003

We prepared $Co_{77}Cr_{20}Ta_3$ Magnetic layer for perpendicular magnetic recording media with introduce Two-step methode and Amorphous Si Underlayer on slide glass substrate. The thickness of magnetic layer were 100nm, and Underlayer were varied from 5 to 100 nm. The multi layer Properties of crystal structure were examined with XRD. Prepared thin films showed improvement of dispersion angle of c-axis orientation ${\Delta}{\theta}_{50}$ caused by inserting Buffer-layer and amorphous Si underlayer.

• Membrane and Water Treatment
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• v.9 no.5
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• pp.327-334
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• 2018

The nano/micro composites with highly porous surface area have attracted of great interest, particularly the synthesis of porous and thin film sheets of high performance. In this paper, an easy method of cost-effective synthesis of thin film ceramic fiber membranes based on Hydroxyapatite, and activated carbon by turned into studied to be applied within the service-facilitated the transport of radioactive waste such as $^{90}Sr$, $^{137}Cs$ and $^{60}Co$) as activated product of radioisotopes from ETRR-2 research reactor and dissolved in 3M $HNO_3$, across a thin flat-sheet supported liquid membrane (TFSSLM). Radionuclides are transported from alkaline pH values. The presence of sodium salts in the aqueous media improves in $HNO_3$, the lowering of permeability because the initial $HNO_3$ concentration is improved. The study some parameters on the thin sheet ceramic supported liquid membrane. EDTA as stripping phase concentration, time of extraction and temperature were studied. The study of maximum permeability of radioisotopes for all parameters. The pertraction of a radioactive waste solution from nitrate medium were examined at the optimized conditions. Under the optimum experimental 98.6-99.9% of $^{90}Sr$, 79.65-80.3% of $^{137}Cs$ and $^{60}Co$ 45.5-55.5% in 90-110 min with were extracted in 10-30 min, respectively. The process of diffusion in liquid membranes is governed by the chemical diffusion process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.9
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• pp.883-887
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• 2006

In order to attain high-rate deposition of Mn-Zn ferrite thin film for soft magnetic underlayer in perpendicular magnetic recording media, a reactive sputtering using powder-metal targets under the mixture gas of Ar and $O_{2}$ was performed. It was succeeded that Mn-Zn ferrite films with (111) crystal orientation were deposited on Pt(111) underlayer without any annealing process. The film revealed 3.4 kG of 4 ${\pi}Ms$, 70 Oe of coercivity. The deposition rate of the new method was 16 times as high as that of the conventional method using ferrite target.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.10a
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• pp.46-46
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• 1988

Structural and magnetic properties of Co-Cr-Mo films were investigated in connection with sputtering conditions. Films were prepared using a convention RF sputtering system. X-ray diffractometry, scanning electron microscopy and transmission electron microscopy were employed to investigate structure properties. Vibrating sample magnetometry was used for coercivity and saturation magnetization measurements. Co-Cr-Mo films displayed reasonable values of perpendicular coercivity and saturation magnetization for perpendicular recording media and showed good perpendicular orientation of the hcp c-axis to the film surface. Perpendicular coercivity was strongly dependent upon substrate technique showed better c-axis orientation than hose using the stationary substrate. Co-Cr-Mo films of 2.9 at. % Mo content showed maximum perpendicular coercivity and saturation magnetization. The films deposited at lower Ar pressure showed good magnetic properties. There was no explicit relationship between the columnar structure and c-axis orientation. Co-Cr-Mo films was found to have suitable structural and magnetic properties for perpendicular recording media.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.690-694
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• 1995

Reducing media noise is a key to realizing high areal recording density. However, perpendicularly oriented Co-Cr films, stong candidates for high density recording media, have received little attention in terms of recording noise. We studied the noise characteristics of Co-Cr based alloy films by varying the compositionally separated structure. Co-Cr films with fine compositionally separated microstructure were observed to have low noise, which recording density dependence were negative or week. Studies on control of the microstructure and magnetic properties in combination with noise analysis are important to realize high density recording media.