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발열 전극에 따른 상변화 메모리 소자의 전자장 및 열 해석
장낙원,마석범,김홍승,Jang, Nak-Won,Mah, Suk-Bum,Kim, Hong-Seung 한국마린엔지니어링학회 2007 한국마린엔지니어링학회지 Vol.31 No.4
PRAM (Phase change random access memory) is one of the most promising candidates for next generation non-volatile memories. However, the high reset current is one major obstacle to develop a high density PRAM. One way of the reset current reduction is to change the heater electrode material. In this paper, to reduce the reset current for phase transition, we have investigated the effect of heater electrode material parameters using finite element analysis. From the simulation. the reset current of PRAM cell is reduced from 2.0 mA to 0.72 mA as the electrical conductivity of heater is decreased from $1.0{\times}10^6\;(1/{\Omega}{\cdot}m$) to $1.0{\times}10^4\;(1/{\Omega}{\cdot}m$). As the thermal conductivity of heater is decreased, the reset current is slightly reduced. But the reset current of PRAM cell is not changed as the specific heat of heater is changed.
기판 열처리에 따른 (Pb, La)TiO₃박막의 유전 특성
박정흠,마석범,박창엽 연세대학교 산업기술연구소 2001 논문집 Vol.33 No.1
(Pb0.72 La0.28)TiO3 thin films were fabricated on the Pt/Ti/SiO2/Si substrated by sol-gel processing. The spin-coated PLT films were sintered at 750℃ for 5min by rapid thermal annealing(RTA). The structural and electrical properties of the PLT thin films deposited annealed and non-annealed substrate were discussed. (Pb0.72 La0.28)TiO3 thin films on substracte annealed at 650[℃], 30[min], had (111) prefer-orientation and high dielectric constant of 1400. We concluded that this (111) prefer-orientation was induced by intermetallic Pt3Ti seed on annealed substrate. Leakage current densities of PLT films thicker than 3300□ were less than 10-7 [A/㎠] order at electric field 150[kV/cm]
레이저 에블레이션법으로 제작된 PLZT 박막의 구조 및 전기적 특성에 관한 연구
장낙원,마석범,백동수,최형욱,박창엽,Jang, Nak-Won,Mah, Suk-Bum,Paik, Dong-Soo,Choi, Hyung-Wook,Park, Chang-Yub 한국전기전자재료학회 1998 전기전자재료학회논문지 Vol.11 No.10
PLZT thin films were fabricated with different Zr/Ti ratios by pulsed laser deposition. PLZT films deposited on Pt/Ti/SiO$_2$/Si substrate. This PLZT thin films of 5000$\AA$ thickness were crystallized at $600^{\circ}C$, $O_2$ pressure 200m Torr. 2/55/45 PLZT thin film showed a maximum dielectric constant value of $\varepsilon$\ulcorner=1550 and dielectric loss was 0.03 at 10kHz. At 2/70/30 PLZT thin film, coercive field and remnant polarization was respectively 19[kV/cm], 8[$\mu$C/$\textrm{cm}^2$]. Raman spectroscopy results showed that the bands of spectra became broader as the amount of Zr mol% increased and two crystal phase coexisted at 2/55/45 PLZT film. Raman spectroscopy was useful for crystal structure analysis of PLZT thin films.
오영광,류주현,마석범,정영호,Oh, Young-Kwang,Yoo, Ju-Hyun,Mah, Suk-Burm,Jeong, Yeong-Ho 한국전기전자재료학회 2011 전기전자재료학회논문지 Vol.24 No.3
In this study, non-stoichiometric 1-x$[(K_{0.5}Na_{0.5})_{0.97}(Nb_{0.96}Sb_{0.04})O_3]$ + x $CeMnO_3$ + 0.8 mol%CuO + 0.2 wt% $Ag_2O$ (x=0, 0.005) ceramics were prepared by a conventional mixed oxide and carbonate method, their dielectric and piezoelectric properties were investigated with the variations of sintering temperature. As $CeMnO_3$ substitution incereased, the density, piezoelectric constant($d_{33}$) and dielectric constant($\varepsilon_r$) were increased and the mechanical quality factor(Qm) was decreased. At the sintering temperature of $1100^{\circ}C$, the density, electromechanical coupling factor($k_p$), dielectric constant($\varepsilon_r$) and piezoelectric constant($d_{33}$) of 0.5mol% $CeMnO_3$ specimen showed the optimun values of 4.475 $g/cm^2$, 0.437, 552 and 166 pC/N, respectively. However, the mechanical quality factor($Q_m$) showed the minimum value of 380.
BaTiO<sub>3</sub> 치환에 따른 NaNbO<sub>3</sub>-LiNbO<sub>3</sub> 세라믹스의 압전 및 유전특성
이상호,류주현,마석범,김성구,Lee, Sang-Ho,Yoo, Ju-Hyun,Mah, Suk-Burm,Kim, Seang-Goo 한국전기전자재료학회 2009 전기전자재료학회논문지 Vol.22 No.3
In this study, in order to develop the composition ceramics for lead-free ultrasonic motor, (1-x-0.09)$NaNbO_{3-x}BaTiO_3-0,09LiNbO_3$ ceramics were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $BaTiO_3$ substitution. All the specimens showed orthorhombic phase structure without secondary phase, $BaTiO_3$ substitution enhanced density, dielectric constant(${\epsilon}_r$) and electromechanical coupling factor($k_p$), However, mechanical quality factor was deteriorated. Curie temperature of specimens was observed as about $380^{\circ}C$. At the $BaTiO_3$ substitution of 4 mol%, density, electromechanical coupling factor($k_p$), dielectric constant(${\epsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum value of $4.493g/cm^3$, 0.236, 175, 70 pC/N, respectively.
레이저 어블레이션에 의한 (Pb,La)$TiO_3$박막의 제작조건에 따른 특성
박정흠,박용욱,마석범 한국전기전자재료학회 2001 전기전자재료학회논문지 Vol.14 No.12
In this study, high dielectric materials, (Pb,La)Ti $O_3$ thin films were fabricated by PLD (Pulsed Laser Deposition) method and investigated in terms of structural and electrical characteristics in order to develope the dielectric materials for the use of new capacitor layers of Giga bit-level DRAM. The deposition conditions were examined in order to fabricate uniform thin films through systematic changes of oxygen pressures and substrate temperature. The uniform thickness and smooth morphology of (P $b_{0.72}$L $a_{0.28}$)Ti $O_3$ thin films were obtained at the conditions of substrate-target distance 5.5[cm], laser energy density 2.1[J/$\textrm{cm}^2$], oxygen pressure 200[mTorr] and substrate temperature 500[$^{\circ}C$]. After the (P $b_{0.72}$L $a_{0.28}$)Ti $O_3$ thin films were fabricated under the above conditions, they were post-annealed by RTA process in order to increase the dielectric constant. The film thickness of 1200 [$\AA$] had dielectric constant 821. Assuming that operating voltage is 2V, leakage current density of (P $b_{0.72}$L $a_{0.28}$)Ti $O_3$ thin films would result into 10$^{-7}$ [A/$\textrm{cm}^2$] and satisfied the specification of 256M DRAM planar capacitor, 4$\times$10$^{-7}$ [A/$\textrm{cm}^2$]m}^2$]