• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.3
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• pp.281-286
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• 2002

In odder to investigate the magnetic properties of CoCr-based bilayered thin films on kind of underlayer, we introduced amorphous Si layer to Co-Cr(-Ta) magnetic layer as underlayer. First, we prepared CoCr and CoCrTa single layer using the Facing Targets Sputtering system to investigate theirs properties. It was revealed that with increasing the film thickness of CoCr, CoCrTa single layer, crystalline orientation and perpendicular coercivity was improved. The CoCrTa thin film showed bettor crystalline and magnetic characteristics than CoCr thin film. As a result of investigating magnetic properties of CoCr and CoCrTa magnetic layer on introducing the Si underlayer, perpendicular coercivity and saturation magnetization of CoCr/Si and CoCrTa/Si bilayered thin film were decreased due to the increased grain size and diffusion of Si atoms to magnetic layer. And they showed constant with increasing the film thickness of Si thin film. However, in case of CoCrTa/Si bilayered thin film, in-plane coercivity was controlled low at about 250Oe. The c-axis orientations of CoCr/si and CoCrTa/Si bilayered thin film showed a good crystalline characteristics as about $2^{\circ}$.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.72-77
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• 1998

The effects of Al micro-bumps on the magnetic properties of CoCr(Pt)Ta/Cr films deposited on glass substrates were investigated. The coercivity increased and the coercivity squareness decreased by incorporating Cr/Al underlayers. The cause of the coercivity increase is attributed to the reduction of Co(0002) texture, the increase of magnetic isolation of CoCr(Pt)/Ta grains, and the refinement of CoCr(Pt)/Ta grains deposited on Cr/Al underlayers. The effects of an Al overlayer on the magnetic properties of CoCr(Pt)Ta/Cr films were also studied. The decrease of coercivity squareness is ascribed to the magnetic isolation of CoCr(Pt)Ta grains.

• Journal of Korean Medicine Rehabilitation
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• v.20 no.2
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• pp.101-111
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• 2010

Objectives : The purpose of this study was to investigate differences between traffic accident and non-traffic accident patients in the early stage, by analysis of the heart rate variability(HRV) and visual analogue scale(VAS). Methods : This study carried out on 38 patients who complained of nuchal or lower back pain. They have received hospital treatment in Dae-Jeon Univ. Cheonan Oriental Hospital. In the TA(Traffic accident) group, the pain caused by TA and in non-TA group, the pain caused by other reasons. We measured HRV and VAS twice(pre-treatment(Tx.) and post-Tx.). Then we analyzed the data. Results : As time goes by, patients who complained of pain showed the inclination to improve ability to balance autonomic nerve system. And fatigue and pain were improved. But they showed the inclination to increase stress index. At pre-Tx., TA group had more stress and worse ability to balance autonomic nerve system, but showed lower fatigue index than non-TA group. But, as time goes by, in TA group the fatigue and autonomic balance got worse. At pre-Tx., non-TA group complained of more severe pain than TA group, but at post-Tx., TA group complained of more severe pain than non-TA group. In other words, in TA group, the decreasing rate of pain was lower than non-TA group. Conclusions : Results from this investigation showed that TA have a negative effect on stress index, ability to balance autonomic nerve system, fatigue index and decreasing rate of pain. These results are expected to consider characteristics of patients who complained of pain caused by TA.

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.288-294
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• 1998

Effect of degree of intermixing at the Ta/NiFe interface induced by varying applied substrate bias voltage during NiFe free layer deposition on change of magnetoresistance in Substrate/Ta/NiFe/Cu/NiFe/FeMn/Ta spin valve multilayers was investigated. It was found that the optimum NiFe free layer thickness showing a maximum MR increase with increasing the bias voltage. The increase of the optimum thickness was due to the increase of the intermixed layer thickness with a bias voltage. The weak ferromagnetic or non ferromagnetic intermixed layer plays as a spin-independent scattering region and does not contribute on spin-dependent scattering. The existence of the intermixed layer was proved by the means of electrical resistivity and magnetization changes. In the present study, the optimum "effective" free layer thickness which gives the highest MR ratio was a constant independent of the magnitude of the bias voltage we have used.have used.

• Journal of the Korean Magnetics Society
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• v.15 no.4
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• pp.226-230
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• 2005

In this research, magnetic properties and annealing effects of the spin valve structures were investigated, which have Ta underlayer deposited with Ar and $N_2$ gas mixture. Also, TaN underlayer as a diffusion barrier and the substrate were investigated. The structure of the spin valve was Si($SiO_2$)/Ta(TaN)/NiFe/CoFe/Cu/CoFe/FeMn/Ta. Deposition rate was decreased and resistivity and roughness of the TaN films were increased as the $N_2$ gas flow was increased. The XRD results after high temperature annealing showed that Silicides were created in Si/Ta layer, but not in Si/TaN layer. Magnetoresistance ratio (MR) and exchange coupling field ($H_{ex}$) were decreased when the $N_2$ gas flow was increased over 4.0 sccm. The MR of the spin valves with Ta and TaN films deposited with up to 4.0 sccm of $N_2$ gas flow was increased about $0.5\%$ until the annealing temperature of up to $200^{\circ}C$ and then, decreased. TaN film deposited with 8.0 sccm of $N_2$ gas flow showed twice the adhesion of the Ta film. The above results indicate that with 3.0 sccm of $N_2$ gas flow during the Ta underlayer deposition, the magnetic properties of the spin valves are maintained, while the underlayer may be used as a diffusion barrier and the adhesion between the Si substrate and the underlayer is increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.11
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• pp.925-928
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• 2011

Perovskite niobates and tantalates have been placed on a short list of functional materials for future technologies. This article was investigated ferroelectric materials $Ag(Ta,Nb)O_3$ thick film. In this study, we have fabricated the $Ag(Ta,Nb)O_3$ thick film on the $Al_2O_3$ substrates by screen printing method. The $Ag(Ta,Nb)O_3$ thick film were fabricated by the mixed oxide method. The sintering temperature and time were 1,150$^{\circ}C$, 2 hr. The electrical properties of $Ag(Ta,Nb)O_3$ thick film were investigated at 30~100$^{\circ}C$.

• The Journal of the Korean Society for Microbiology
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• v.22 no.2
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• pp.185-193
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• 1987

Ten species of herbae, which have been used to treat cancers in Chinese medicine, were tested to investigate their mutagenicity or antimutagenicity in S. typhimurium TA97, TA98, TA100, TA1535, and TA1538. Scolopendra centipede was weakly active in reversion of the frameshift mutation in S. typhimurium TA97 strain and the base-pair substitution in TA100 and TA1535 strains. Other herbae such as Coix lachryma, Dianthus superbus, Tricanthoshse kirilowii, Eupatorium formosanum, Lithospermum erythrorhizon, Ansaema japonicum, Curcuma zedoaria, Helicteres angustifolia, and Euonymus sieboldianus did not show any of the mutagenic potential, regardless of the metabolic activation with rat hepatic microsomal fraction. Dianthus superbus, Eupatorium formosanum, and Euonymus sieboldianus exhibited suppressive activities on microbial mutagenesis of N-methyl-N'-nitrosoguanidine, a base-pair substitution mutagen, in TA1535 and TA100 tester strains. The antimutagenic activities of Dianthus superbus and Euonymus sieboldianus appeared to be dose-dependant.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.881-885
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• 2001

Kinetics and mechanisms of intermediate phases formation in $Ba(Mg_{1/3}Ta_{2/3})O_3$, obtained by a solid state reaction were studied. $Ba{Ta_2}{O_6}$ and ${Ba_4}{Ta_2}{O_9}$ as intermediate products were first formed at $700^{\circ}C$. $Ba(Mg_{1/3}Ta_{2/3})O_3$ was appeared at $800^{\circ}C$. Several reactions take place on heating process. $Ba{Ta_2}{O_6}$ is found at the first stage of the reaction, and then $Ba{Ta_2}{O_6}$ or ${Ba_4}{Ta_2}{O_9}$ react with MgO to form $Ba(Mg_{1/3}Ta_{2/3})O_3$. The reaction of $Ba(Mg_{1/3}Ta_{2/3})O_3$ formation does not complete until fired at $1350^{\circ}C$ for 60 min. The kinetics of solid-state reaction between powdered reactants was controlled by diffusion mechanism, and can be explained by the Jander's model for three-dimensional diffusion.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1502-1504
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• 2003

최근 전자기기의 경박단소화 추세는 전자기기의 크기와 가격의 감소를 이끌었으며 이러한 추세는 앞으로 지속될 것이다. 이와 같은 현상으로 전자기기를 구성하는 요소의 절반이상을 차지하는 단위수동소자의 경우 소형화를 넘어 박막화 및 집적화가 절실히 요구되는 실정이다. 따라서 본 연구에서는 현재 GHz 대역의 휴대용 무선통신 송 수신부 등에 사용되고 있는 기판이 $Al_2O_3$ 기판인 점을 고려하여 기판의 공통화를 위해 $Al_2O_3$ 기판 위에 Ta/$Ta_2O_5$/Ta 구조를 갖는 MIM 박막커패시터를 제작하여 그 특성을 고찰하였다. 모든 박막의 증착은 RF-magnetron reactive sputtering법에 의해 이루어졌으며, 유전체 열처리는 $700^{\circ}C$ 진공상태에서 60 sec 동안 수행하였다. XRD 분석결과, as-deposited $Ta_2O_5$ 박막은 열처리 후에 비정질상에서 결정질상으로 변환되었다. Ta/$Ta_2O_5$/Ta/Ti/$Al_2O_3$ 커패시터의 전기적 특성으로는 C-F, C-V, I-V 를 측정하였다.

• Korean Journal of Materials Research
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• v.12 no.10
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• pp.814-819
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• 2002

TiN and TaN films as electrode materials of reactive sputtered $Ta_2$$O_{5}$ were prepared by sputtering to compare their thermal stabilities with $Ta_2$$O_{5}$ The microstructural change of $Ta_2$$O_{5}$ films with annealing was also investigated. As- deposited $Ta_2$$O_{5}$ film on $SiO_2$ was amorphous and annealing of 80$0^{\circ}C$ for 30 min made it transform to $\beta$-Ta$_2$O$_{5}$ crystalline which contains amorphous particles with the size of a few nm. Crystallization temperature of Ta$_2$Ta_2$$O_{5}$ on TaN is higher than that on TiN electrode. The interface between TaN and Ta$_2$O$_{5}$ maintained stably even after vacuum annealing up to $800^{\circ}C$ for 1 hr, but TiN interacted with $Ta_2$$_O{5}$ and so interdiffusion between TiN and $Ta_2$$O_{5}$ occurred by vacuum annealing of 80$0^{\circ}C$ for 1 hr. It indicates that TaN is thermally more stable with $Ta_2$$O_{5}$ than TiN.N.