• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 춘계연구발표회 논문개요집
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• pp.124-125
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• 2002

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2000년도 International Symposium on Magnetics The 2000 Fall Conference
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• pp.325-326
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• 2000

Low temperature diagnosis was performed as a probe for the integrity of MTJ(Magnetic tunnel junction) process which is optimised for the given plasma oxidation condition. TMR ratio increased slowly with decreasing temperature than that expected from spin wave exitation theory〔1〕. Junction resistance (RJ) does not follow T$\^$-$\frac{1}{2}$/ law below 200 K, indicating another conduction path besides spin polarized tunneling is involved at low temperature. Temperature dependence of conductance dip and bias dependence of TMR with temperature are discussed, from which the quality of tunnel barrier and its formation process can be inferred.

• Journal of Magnetics
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• 제11권1호
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• pp.25-29
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• 2006

Recent experiments have demonstrated high TMR ratios in MTJs with the MgO barrier [1,2]. The CoFeB/MgO/CoFeB junctions showed better properties than the CoFe/MgO/CoFe junctions because the MgO layer had a good crystalline structure with (001) texture and smooth and sharp interface between CoFeB/MgO [3]. The amorphous CoFeB with 20 at%B starts the crystallization at $340^{\circ}C$ [4] and this crystallization of the CoFeB helps obtaining the high TMR ratio. In this work, the compositional changes in the MgO barrier and at the interface of CoFeB/MgO/CoFeB after the CoFeB crystallization were studied in annealed MTJs. XPS depth profiles were utilized. TEM analyses showed that the MgO barrier had (100) texture on CoFeB in the junctions. B in the bottom CoFeB layer diffused into the MgO barrier and B-oxide was formed at the interface of CoFeB/MgO/CoFeB after the CoFeB crystallization.

• Journal of Magnetics
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• 제9권1호
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• pp.17-22
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• 2004

We studied the magnetotransport properties of tunnel junctions with AlO and AlN barriers fabricated using microwave-excited plasma. The plasma nitridation process provided wider controllability than the plasma oxidization for the formation of MTJs with ultra-thin insulating layer, because of the slow nitriding rate of metal Al layers, comparing with the oxidizing rate of them. High tunnel magnetoresistance (TMR) ratios of 49 and 44% with respective resistance-area product $(R{\times}A) of 3 {\times} 10^4 and 6 {\times} 10^3 {\Omega}{\mu}m^2$ were obtained in the Co-Fe/Al-N/Co-Fe MTJs. We conclude that AlN is a hopeful barrier material to realize MTJs with high TMR ratio and low $R{\times}A$ for high performance MRAM cells. In addition, in order to clarify the annealing temperature dependence of TMR, the local transport properties were measured for Ta $50{\AA} /Cu 200 {\AA}/Ta 50 {\AA}/Ni_{76}Fe_{24} 20 {\AA}/Cu 50 {\AA}/Mn_{75}Ir_{25} 100 {\AA}/Co_{71}Fe_{29} 40 {\AA}/Al-O$ junction with $d_{Al}= 8 {\AA} and P_{O2}{\times}t_{0X}/ = 8.4 {\times} 10^4$ at various temperatures. The current histogram statistically calculated from the electrical current image was well in accord with the fitting result considering the Gaussian distribution and Fowler-Nordheim equation. After annealing at $340^{\circ}C$, where the TMR ratio of the corresponding MTJ had the maximum value of 44%, the average barrier height increased to 1.12 eV and its standard deviation decreased to 0.1 eV. The increase of TMR ratio after annealing could be well explained by the enhancement of the average barrier height and the reduction of its fluctuation.

• Journal of Magnetics
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• 제11권4호
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• pp.170-181
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• 2006

Spin dependent tunneling has enormously activated the field of magnetism in general, and in particular spin transport studies, in the past ten years. Thousands of articles related to the subject have appeared with many fundamental results. Importantly, there is great interest in their potential for application. There was another surge of activity in this field since the past five years - created by the theoretical prediction of a large tunnel magnetoresistance that arises due to band symmetry matched coherent tunneling in epitaxial magnetic tunnel junctions with (001) MgO barrier and experimentally well demonstrated. This further development in the field has boosted the excitement in both fundamental science as well as the possibility of application in such as magnetic random access memory, ultra sensitive read heads, biosensors and spin torque diodes. This review is a brief coverage of the field highlighting the literature that deals with magnetic tunnel junctions having epitaxial MgO tunnel barriers.

• 터널과지하공간
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• 제19권3호
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• pp.226-235
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• 2009

터널내 자연환기력은 터널의 정상운영시 뿐만 아니라 터널내 화재와 같은 비상시에 기류 유동상의 심각한 문제를 야기할 수 있다. 따라서 자연환기력의 영향은 터널 환기 및 방재시스템 설계시에 반드시 고려하여야한다. 자연환기력의 결정에 영향을 미치는 변수에는 지형, 기상, 터널의 물리적 특성에 관련된 다양 변수들이 포함된다. 그러나 이들 변수간의 정량적인 관계의 이해가 복잡하여 현재 어떤 나라에서도 국가기준에 자연환기력의 예측방법을 제시하고 있지 않다. 본 논문에서는 국내 고속도로터널을 대상으로 자연환기력의 정량화 연구를 수행하였다. 정량화를 위하여 첫째, 양 갱구의 기압차 측정방법, 둘째, 피스톤효과에 의한 영향을 제거하는 방법, 셋째, 기압장벽고 방법을 적용하였다.

• 한국지열·수열에너지학회논문집
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• 제14권3호
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• pp.21-28
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• 2018

This paper presents two-step simulations to calculate the influence of blast-induced pressures on explosion-protection valves installed at the boundary between a protection facility and a tunnel entering the facility. The first step is to calculate the respective overpressure on the entrance and exit of the tunnel when an explosion occurs near the tunnel entrance and exit to approach the protection facility. Secondly, the blast pressures on the explosion-protection valves mounted to walls located near the tunnel inside approaching the protection facility are analyzed with a 0.1 ms time variation using the results obtained from the first-step calculations. The following conclusions could be derived as a results: (1) The analysis of the entrance tunnel scenario, P1, leads to the maximum overpressure of 47 kPa, approximately a half of the ambient pressure, at the inner entrance due to the effect of blast barrier. For the scenario, P2, the case not blocked by the barrier, the maximum overpressure is 628 kPa, which is relatively high, namely, 5.2 times the ambient pressure. (2) It is observed that the pressure for the entrance tunnel is effectively mitigated because the initial blast pressures are partially offset from each other according to the geometry of the entrance and a portion of the pressures is discharged to the outside.

• 한국터널지하공간학회 논문집
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• 제12권2호
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• pp.145-155
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• 2010

최근 국내에서는 해저터널에 대한 관심이 늘고 있고, 실제 해저터널의 건설아 진행되고 있다. 이러한 해저터널의 안정성을 위해서는 차수 및 보강을 위해 그라우팅이 필수적이다. 따라서 본 연구에서는 해저 심부에 위치한 터널을 대상으로 그라우팅 보장이 터널의 안정성에 미치는 영향을 살펴보았다. 이를 위해 1, 3, 5 등급 암반을 대상으로 그라우팅 보강영역, 암반등급, 숏크리트 두께, 측압계수, 그라우팅 두께, 펌핑의 유무를 달리하여 민감도 분석을 위한 수리-역학적 연계해석을 수행하였다. 수치해석을 위해 FLAC-2D ver 5.0을 사용하였다. 해저터널의 그라우팅 보강 설계를 수행할 경우에는 그라우팅의 강도증가 효과뿐만 아니라 그라우팅 차수로 인해 증가되는 수압의 효과도 같이 고려해야 할 것으로 판단된다.

• KIEAE Journal
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• 제2권1호
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• pp.55-61
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• 2002

It seems inevitable for residential buildings to be high-rise and allocated near traffic roads due to the overcrowding in urban area. Acoustic environment in those residential buildings has been seriously deteriorated by the increase of traffic vehicles. Commonly used sound barriers have a limitation in controlling noise diffracted over the boundary of a sound barrier and hence are not effective to attenuate noise especially for the residential units in high level. The use of an enclosed noise barrier can be an alternative to supplement the defects of conventional noise barriers. The present work aims at providing useful data in designing enclosed noise barriers for residential areas adjacent to roads. Number of field measurements for various noise barriers and enclosed noise barriers were carried out and the results were discussed with relation to the proper design of enclosed noise barriers.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.134-135
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• 2008

Ultra-thin $SiO_2/ZrO_2$ dielectrics were deposited by atomic layer chemical vapor deposition (ALCVD) method for non-volatile memory application. Metal-oxide-semiconductor (MOS) capacitors were fabricated by stacking ultra-thin $SiO_2$ and $ZrO_2$ dielectrics. It is found that the tunneling current through the stacked dielectric at the high voltage is lager than that through the conventional silicon oxide barrier. On the other hand, the tunneling leakage current at low voltages is suppressed. Therefore, the use of ultra-thin $SiO_2/ZrO_2$ dielectrics as a tunneling barrier is promising for the future high integrated non-volatile memory.