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Magnetic Tunnel Junctions with AlN and AlO Barriers
Tae Sick Yoon,Satoru Yoshimura,Masakiyo Tsunoda,Migaku Takahashi,Bum Chan Park,Young Woo Lee,Ying Li,Chong Oh Kim 한국자기학회 2004 Journal of Magnetics Vol.9 No.1
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 × A) of 3 × 10⁴ and 6 × 10³ Ωμ㎡ 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 × 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 Å/Cu 200 Å/Ta 50 Å/Ni_(76)Fe₂₄ 20 Å/Cu 50 Å/Mn_(75)Ir_(25) 100 Å/Co_(71)Fe_(29) 40 Å/Al-O junction with d_(Al) = 8 Å and P_(O2) × t_(OX) = 8.4 × 10⁴ L 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 ℃, 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.
마이크로파 여기 프라즈마법으로 제조한 강자성 터널링 접합의 국소전도특성
윤대식(Tae Sick Yoon),김철기(Cheol Gi Kim),김종오(Chong-Oh Kim),Masakiyo Tsunoda(Masakiyo Tsunoda),Migaku Takahashi(Migaku Takahashi),Ying Li(Ying Li) 한국자기학회 2003 韓國磁氣學會誌 Vol.13 No.2
Ferromagnetic tunnel junctions were fabricated by dc magnetron sputtering and plasma oxidation process. The local transport properties of the ferromagnetic tunnel junctions were studied using contact-mode Atomic Force Microscopy (AFM) and the local current-voltage analysis. Tunnel junctions with the structure of sub./Ta/Cu/Ta/NiFe/Cu/Mn_(75)Ir_(25)/Co_(70)Fe_(30)/Al-oxide were prepared on thermally oxidized Si wafers. Al-oxide layers were formed with microwave excited plasma using radial line slot antenna (RLSA) for 5 and 7 sec. Kr gas was used as the inert gas mixed with O₂ gas for the plasma oxidization. No correlation between topography and current image was observed while they were measured simultaneously. The local current distribution was well identified with the distribution of local barrier height. Assuming the gaussian distribution of the local barrier height, the ferromagnetic tunnel junction with longer oxidation time was well fitted with the experimental results. As contrast, in the case of the shorter time oxidation junction, the current mainly flow through the low barrier height area for its insufficient oxygen. Such leakage current might result in the decrease of tunnel magnetoresistance (TMR) ratio.
Yoon, Heung-Sick,Kim ,Kyong-Tae Korean Chemical Society 1985 Bulletin of the Korean Chemical Society Vol.6 No.5
Cyanoisopropyl radical derived from azobisisobutyronitrile (AIBN) by either thermolysis or photolysis reacts with oxygen to give cyanoisopropylperoxy radical which then was converted to acetone and cyano radical and/or acetyl cyanide and methyl radical. Of these products, acetone formed was quantitatively determined by the addition of thianthrene cation radical perchlorate to the reaction mixture. The results showed that 55.7 mmol, 16.9 mmol, and 16.0 mmol of acetone were formed for 7 hours from 1 mol of AIBN at $82{\pm}1^{\circ}C$ in acetonitrile, carbon tetrachloride, and benzene, respectively. However, 22.2 mmol of acetone was formed from photolysis of 1 mmol of AIBN in acetonitrile. The value decreased to 13.2 mmol by bubbling argon into the solvent prior to photolysis.
척추 지주막하강내 Morphine 주입후 발생한 호흡정지 2 예
김태요,송윤식,송희선 대한마취과학회 1981 Korean Journal of Anesthesiology Vol.14 No.3
Epidural and subarachnoid narcotics have raised new possibilities for selective blockade of pain transmission at the spinal cord level. However, it must still be regarded as an experimental technique until detailed pharmacological and physiological data are available, since many reports have treated the development of respiratory arrest which may be related to the dynamics of CSF flow. We experienced 2 cases of respiratory arrest after intrathecal injection of 2mg morphine. One patient developed respiratory arrest at approximately 5 1/2hours after intrathecal morphine and the other at approxmately 12 1/2hours. Those respiratory arrests were completely reversed with naloxone hydrochloride without interfering with the analgesic effect of the drug.
한국 산업단지 인근 연안 어류의 성비와 intersexuality
이정식 ( Jung Sick Lee ),김재원 ( Jae Won Kim ),박정준 ( Jung Jun Park ),주선미 ( Sun Mi Ju ),박지선 ( Ji Seon Park ),이동근 ( Dong Geun Lee ),윤태웅 ( Tae Woong Yun ),최경희 ( Kyung Hee Choi ),윤준헌 ( Jun Heon Yoon ),엄익춘 ( Ig 한국어병학회 2010 한국어병학회지 Vol.23 No.2
Specimens were collected from the coastal region near industrial complex of Ulsan-Onsan, Sihwa-Ansan and Yeosu-Gwangyang in 2008 and 2009. The total number of individuals used in analysis was 1,289 of Acanthogobius flavimanus, Chelon haematocheilus, Hemibarbus labeo, Leiognathus nuchalis, Mugil cephalus and Synechogobius hasta. The sex ratio in the total individual was 1:0.73 (female:male). Specific sex ratio of fishes in the areas, namely the Ulsan-Onsan, Sihwa-Ansan and Yeosu-Gwangyang were 1:0.79, 1:0.81, and 1:0.25, respectively. Especially, female in Yeosu-Gwangyang was higher than male. The intersexuality in the total individual was 11.7%. Intersexuality of fishes in the areas were 4.98, 14.39 and 25.0% in the Ulsan-Onsan, Sihwa-Ansan and Yeosu-Gwangyang, respectively. It was indicated female higher than male in Ulsan-Onsan and male higher than female in Sihwa-Ansan and Yeosu-Gwangyang.
Magnetic Properties and Magnetoimpedance Effect in Mumetal Thin Films
Wan-Shik Cho,Tae-Sick Yoon,Heebok Lee,Chong-Oh Kim 한국자기학회 2001 Journal of Magnetics Vol.6 No.1
The dependence of the magnetoimpedance effect (MI) on magnetic properties has been investigated in mumetal thin films prepared by rf magnetron sputtering. Coercivity of thin films prepared at 400 W was about 0.4 Oe, and the magnetic anisotropy field of films deposited under a uniaxial magnetic field decreased with increasing film thickness. The saturation magnetization of mumetal films increased with rising input power and thickness, and was smaller than that of permalloy films. Transverse incremental Permeability (TPR) of films of 1 ㎛ thick increased with increasing effective permeability. The magneto impedance ratio (MIR) was proportional to TPR in films 1 ㎛ thick but in spite of lower effective permeability at higher thicknesses, MIR increased due to skin effect. The height of the double peaks in the MIR curves decreased with decreasing anisotropy and thickness. The maximum MIR value for a 4 ㎛ thick 75 % at 36.5 ㎒.
Kazuhiro Nishikawa,Satoshi Ogata,Toshihiro Shoyama,Wan-Sick Cho,Tae-Sick Yoon,Masakiyo Tsunoda,Migaku Takahashi 한국자기학회 2002 Journal of Magnetics Vol.7 No.3
Three fabrication techniques for forming thin barrier layer with uniform thickness and large barrier height in magnetic tunnel junction (MTJ) are discussed. First, the effect of immiscible element addition to Cu layer, a high conducting layer generally placed under the MTJ, is investigated in order to reduce the surface roughness of the bottom ferromagnetic layer, on which the barrier is formed. The Ag addition to the Cu layer successfully realizes the smooth surface of the ferromagnetic layer because of the suppression of the grain growth of Cu. Second, a new plasma source, characterized as low electron energy of 1 eV and high density of 10¹² ㎝-³, is introduced to the Al oxidation process in MTJ fabrication in order to reduce damages to the barrier layer by the ion-bombardment. The magnetotransport properties of the MTJs are investigated as a function of the annealing temperature. As a peculiar feature, the monotonous decrease of resistance area product (RA) is observed with increasing the annealing temperature. The decrease of the RA is due to the decrease of the effective barrier width. Third, the influence of the mixed inert gas species for plasma oxidization process of metallic Al layer on the tunnel magnetoresistance (TMR) was investigated. By the use of Kr-O₂ plasma for Al oxidation process, a 58.8% of MR ratio was obtained at room temperature after annealing the junction at 300℃, while the achieved TMR ratio of the MTJ fabricated with usual Ar-O₂ plasma remained 48.4%. A faster oxidization rate of the Al layer by using Kr-O₂ plasma is a possible cause to prevent the over oxidization of Al layer and to realize a large magnetoresistance.
윤대식,이영,박범찬,김철기,김종오,Yoon, Tae-Sick,Tsunoda, Masakiyo,Takahashi, Migaku,Li, Ying,Park, Bum-Chan,Kim, Cheol-Gi,Kim, Chong-Oh 한국재료학회 2003 한국재료학회지 Vol.13 No.4
Ferromagnetic tunnel junctions, Ta/Cu/Ta/NiFe/Cu/$Mn_{75}$ $Ir_{25}$ $Co_{70}$ $Fe_{30}$/Al-oxide, were fabricated by do magnetron sputtering and plasma oxidation process. The effect of annealing temperature on the local transport properties of the ferromagnetic tunnel junctions was studied using contact-mode Atomic Force Microscopy (AFM). The current images reflected the distribution of the barrier height determined by local I-V analysis. The contrast of the current image became more homogeneous and smooth after annealing at $280^{\circ}C$. And the average barrier height $\phi_{ave}$ increased and its standard deviation $\sigma_{\phi}$ X decreased. For the cases of the annealing temperature more than $300^{\circ}C$, the contrast of the current image became large again. And the average barrier height $\phi_{ave}$ decreased and its standard deviation $\sigma_{\phi}$ increased. Also, the current histogram had a long tail in the high current region and became asymmetric. This result means the generation of the leakage current that is resulted from the local generation of a low barrier height region. In order to obtain the high tunnel magnetoresistance(TMR) ratio, the increase of the average barrier height and the decrease of the barrier height fluctuation must be strictly controlled.led.