• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.3
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• pp.276-283
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• 2005

Magnetic tunneling transistor (MTT) device using the amorphous n-type Si semiconductor film for base and collector consisting of the [CoFe/NiFe](free layer) and Si(top layer) multilayers was used to study the spin-dependent hot electron magnetocurrent (MC) and tunneling magnetoresistance (TMR) at room temperature. A large MC of 40.2 % was observed at the emitter-base bias voltage ( $V_{EB}$ ) of 0.62 V. The increasing emitter hot current and transfer ratio ( $I_{C}$/ $I_{E}$) as $V_{EB}$ are mainly due to a rapid increase of the number of conduction band states in the Si collector. However, above the $V_{EB}$ of 0.62 V, the rapid decrease of MC was observed in amorphous Si-based MTT because of hot electron spin-dependent elastic scattering across CoFe/Si interfaces.

• Journal of the Korean Magnetics Society
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• v.12 no.6
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• pp.201-205
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• 2002

The tunneling magnetoresistance (TMR) of a ramp-edge type junction has been studied. The samples with a structure of NiO(60)/Co(10)/NiO(60)/Si$_3$N$_4$(2-6)/NiFe(10) (nm) were prepared by the sputtering and etched by the electron cyclotron (ECR) argon ion milling. Nonlinear I-V characteristics was obtained from a ramp-type tunneling junctions having the dominant difference between zero and ＋90 Oe perpendicular to the junction edge line. The voltage dependence of TMR was stable up to a bias volt of $\pm$10 V with a TMR ratio of about -10%, which may be very peculiar magnetic tunneling properties with asymmetric tunneling process between wedge Co pinned layer and NiFe free layer.

• Nuclear Engineering and Technology
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• v.53 no.8
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• pp.2682-2695
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• 2021

This paper aims to evaluate the structural dynamic responses and damage/failure of the nuclear fuel reprocessing plant under the free drop impact of spent fuel cask (SFC) and fuel assembly (FA) during the on-site transportation. At the present Part I of this paper, the large-scale SFC model free drop test and the corresponding numerical simulations are performed. Firstly, a composite target which is composed of the protective structure, i.e., a thin RC plate (representing the inverted U-shaped slab in the loading shaft) and/or an autoclaved aerated concrete (AAC) blocks sacrificial layer, as well as a thick RC plate (representing the bottom slab in the loading shaft) is designed and fabricated. Then, based on the large dropping tower, the free drop test of large-scale SFC model with the mass of 3 t is carried out from the height of 7 m-11 m. It indicates that the bottom slab in the loading shaft could not resist the free drop impact of SFC. The composite protective structure can effectively reduce the damage and vibrations of the bottom slab, and the inverted U-shaped slab could relieve the damage of the AAC blocks layer dramatically. Furthermore, based on the finite element (FE) program LS-DYNA, the corresponding refined numerical simulations are performed. By comparing the experimental and numerical damage and vibration accelerations of the composite structures, the present adopted numerical algorithms, constitutive models and parameters are validated, which will be applied in the further assessment of drop impact effects of full-scale SFC and FA on prototype nuclear fuel reprocessing plant in the next Part II of this paper.

• Journal of the Korean Magnetics Society
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• v.27 no.3
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• pp.82-86
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• 2017

The IrMn based GMR-SV films with three different buffer layers were prepared on Corning glass by using ion beam deposition and DC magnetron sputtering method. The major and minor magnetoresistance curves for three different buffer layers beneath the structure of NiFe(15 nm)/CoFe(5 nm)/Cu(2.5 nm)/CoFe(5 nm)/NiFe(7 nm)/IrMn(10 nm)/Ta(5 nm) at room temperature have shown different magnetoresistance properties. When the samples were annealed at $250^{\circ}C$ in vacuum, the magnetoresistance ratio, the coercivity of pinned ferromagnetic layer, and the interlayer coupling field of free ferromagnetic layer were enhanced while the exchange bias coupling field did not show noticeable changes.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.169-169
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• 2011

STT-MRAM (수직자화 자기메모리)는 자화반전 현상을 원리로 구동하는 비휘발성 메모리로 기존의 메모리 장치에 비해 빠른 접근 속도와 높은 저장 밀도를 가지며 영구적인 기록이 가능하다. 이러한 장점들에 더해 적은 소모 전력을 지니므로 기존의 SRAM등의 한계를 극복할 대안으로 각광받고 있으며 차세대 메모리 군의 선두주자로 가장 적합한 후보중 하나이다. STT-MRAM의 건식 식각 방식에 있어 가장 큰 이슈는 소자 구동에 핵심적인 역할을 하는 MTJ(Magnetic Tunnel Junction)의 식각이다. MTJ는 free layer, tunnel barrier, pinned layer 3개의 층으로 구성되어 있으며 양 끝 layer에는 강자성체인 CoFeB가 사용되고 tunnel barrier에는 절연층인 MgO가 사용되고 있다. 이러한 물질들은 기존의 반도체 소자에서는 사용되지 않았던 물질들로 기존 공정에서 사용되던 Cl2 based plasma etching에서는 측벽에 비화발성 반응물과 잔류 Cl2에 의해 부식이 발생하는 문제점이 드러나고 있다. 이러한 문제점을 해결하기 위한 새로운 대안으로 CO/NH3/Ar나 CH4/Ar 같은 새로운 가스 조합을 사용하는 연구가 진행되고 있다. 이러한 연구에 의해 기존의 Cl2 plasma를 이용한 식각에서 나타나는 문제점은 해결이 되었으나 또 다른 문제점들이 보고되고 있다. 본 연구에서는 stack MRAM sample을 사용하여 기존의 사용되는 Cl2/Ar plasma와 대안 gas인 CO/NH3, CH4/Ar plasma에서의 식각을 진행하였으며 실험 조건(gas 비율 변화, Bias power 변화, 식각 시간)에 따른 식각 속도의 변화나 식각 후의 profile에 대하여 관찰하였다. 이에 따라 식각후에 어떠한 차이점이 있는 지를 알아보았으며 CO/NH3나 CH4/Ar plasma에서 식각시 나타나는 문제점에 대하여도 조명해 보았다.

• Proceedings of the Korean Magnestics Society Conference
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• 2005.12a
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• pp.198-199
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• 2005

• Korean Journal of Materials Research
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• v.29 no.1
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• pp.52-58
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• 2019

The microstructure, hardness, and wear behaviors of a High Velocity Oxygen Fuel(HVOF) sprayed WC-CoFe coating are comparatively investigated before and after laser heat treatments of the coating surface. During the spraying, the binder metal is melted and a small portion of WC is decomposed to $W_2C$. A porous coating is formed by evolution of carbon oxide gases formed by the reaction of the free carbon and the sprayed oxygen gas. The laser heat treatment eliminates the porosity and provides a more densified microstructure. After laser heat treatment, the porosity in the coating layer decreases from 1.7 % to 1.2 and the coating thickness decreases from $150{\mu}m$ to $100{\mu}m$. The surface hardness increases from 1440 Hv to 1117 Hv. In the wear test, the friction coefficient of coating decreases from 0.45 to 0.32 and the wear resistance is improved by the laser heat treatment. The improvement is likely due to the formation of oxide tribofilms.

• Proceedings of the Korean Magnestics Society Conference
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• 2011.12a
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• pp.74-74
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• 2011

• Proceedings of the Korean Magnestics Society Conference
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• 2005.12a
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• pp.8-9
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• 2005

• Proceedings of the Korean Magnestics Society Conference
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• 2012.05a
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• pp.74-75
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• 2012