• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.851-856
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• 2003

We have investigated the material and electrical properties of $Bi_{4-x}La_xTi_3O_{12}$ (BLT) ferroelectric thin film for ferroelectric nonvolatile memory applications of capacitor type and single transistor type. The 120nm thick BLT films were deposited on $Pt/Ti/SiO_2/Si$ and $SiO_2/Nitride/SiO_2$ (ONO) substrates by the sol-gel spin coating method and were annealed at $700^{\circ}C$. It was observed that the crystallographic orientation of BLT thin films were strongly affected by the excess Bi content and the intermediate rapid thermal annealing (RTA) treatment conditions regardeless of two type substrates. However, the surface microstructure and roughness of BLT films showed dependence of two different type substrates with orientation of (111) plane and amorphous phase. As increase excess Bi content, the crystallographic orientation of the BLT films varied drastically in BLT films and exhibited well-crystallized phase. Also, the conversion of crystallographic orientation at intermediate RTA temperature of above $450^{\circ}C$ started to be observed in BLT thin films with above excess 6.5% Bi content and the rms roughness of films is decreased. We found that the electrical properties of BLT films such as the P-V hysteresis loop and leakage current were effectively modulated by the crystallographic orientations change of thin films.

• 전기학회논문지
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• 제67권4호
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• pp.543-548
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• 2018

Ferroelectric $Bi_4Ti_3O_{12}$ films were deposited on $SrTiO_3(100)$ and Si(100) substrate by using conductive $SrRuO_3$ films as underlayer, and their ferroelectric and electrical properties were investigated depending on crystal structure and orientation. C-axis oriented $Bi_4Ti_3O_{12}$ films were grown on well lattice-matched pseudo-cubic $SrRuO_3$ films deposited on $SrTiO_3(100)$ substrate, while random-oriented polycrystalline $Bi_4Ti_3O_{12}$ films were grown on $SrRuO_3$ films deposited on Si(100) substrate. The random-oriented polycrystalline film showed a good ferroelectric hysteresis property with remanent polarization ($P_r$) of $9.4{\mu}C/cm^2$ and coercive field ($E_c$) of 84.9 kV/cm, while the c-axis oriented film showed $P_r=0.64{\mu}C/cm^2$ and $E_c=47kV/cm$ in polarizaion vs electric field curve. The c-axis oriented $Bi_4Ti_3O_{12}$ film showed a dielectric constant of about 150 and lower thickness dependence in dielectric constant compared to the random-oriented film. Furthermore, the c-axis oriented $Bi_4Ti_3O_{12}$ film showed leakage current lower than that of the polycrystalline film. The difference of ferroelectric properties in two films was explained from the viewpoint of depolarization effect due to orientation of spontaneous polarization and layered crystal structure of bismuth-base ferroelectric oxide.

• 한국초전도ㆍ저온공학회논문지
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• 제19권1호
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• pp.30-35
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• 2017

The effects of the crystallographic orientation and sample thickness on the magnetic levitation forces (F) and trapped magnetic field (B) of single grain YBCO bulk superconductors were examined. Single grain YBCO samples with a (001), (110) or (100) surface were used as the test samples. The samples used for the force-distance (F-d) measurement were cooled at 77 K without a magnetic field (zero field cooling, ZFC), whereas the samples used for the B measurement were cooled under the external magnetic field of a Nd-B-Fe permanent magnet (field cooling, FC). It was found that F and B of the (001) surface were higher than those of the (110) or (100) surface, which is attributed to the higher critical current density ($J_c$) of the (001) surface. For the (001) samples with t=5-18 mm, the maximum magnetic levitation forces ($F_{max}s$) of the ZFC samples were larger than 40 N. About 80% of the applied magnetic field was trapped in the FC samples. However, the F and B decreased rapidly as t decreased below 5 mm. There exists a critical sample thickness (t=5 mm for the experimental condition of this study) for maintaining the large levitation/trapping properties, which is dependent on the material properties and magnitude of the external magnetic fields.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.177-180
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• 2002

Thickness dependence of crystallographic orientation of diol based sol-gel derived PZT(52/48) films on dielectric and piezoelectric properties was investigated The thickness of each layer by one time spinning was about 0.2 $\mu\textrm{m}$, and crack-free films was successfully deposited on 4 inches Pt/Ti/SiO$_2$/Si substrates by 0.5 mol solutions in the range from 0.2 $\mu\textrm{m}$ to 3.8 $\mu\textrm{m}$. Excellent P-E hysteresis curves were achieved without pores or any defects between interlayers. As the thickness increased , the (111) preferred orientation disappeared from 1$\mu\textrm{m}$ to 3 $\mu\textrm{m}$ region, and the orientation of films became random above 3 $\mu\textrm{m}$. Dielectric constants and longitudinal piezoelectric coefficient d$\_$33/, measured by pneumatic method were saturated around the value of about 1400 and 300 pC/N respectively above the thickness of 0.8 7m. A micromachined piezoelectric cantilever have been fabricated using 0.8 $\mu\textrm{m}$ thickness PZT (52/48) films. PZT films were prepared on Si/SiN$\_$x/SiO$_2$/Ta/Pt substrate and fabricated unimorph cantilever consist of a 0.8 fm thick PZT layer on a SiNx elastic supporting layer, which becomes vibration when ac voltage is applied to the piezoelectric layer. The dielectric constant (at 100 kHz) and remanent polarization of PZT films were 1050 and 25 ${\mu}$C/$\textrm{cm}^2$, respectively. Electromechanical characteristics of the micromachined PZT cantilever in air with 200-600 $\mu\textrm{m}$ lengths are discussed in this presentation.

• 열처리공학회지
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• 제22권3호
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• pp.155-161
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• 2009

An investigation of the deformation behavior of ${\gamma}'-Ni_3Al$ single crystals containing fine dispersion of disordered ${\gamma}$ particles was performed for several different crystal orientations. Deformation structures were observed by the weak-beam method of transmission electron microscopy (TEM). The critical resolved shear stress (CRSS) for (111) [$\bar{1}$01] slie. increases with increasing temperature in the temperature range where (111) slip operates. The CRSS for (111) [$\bar{1}$01] slip is dependent on crystal orientation in the corresponding temperature range. The temperature where the strenjlth reaches a maximum is dependent on crystal orientation; the higher the ratio of the Schmid factors of (010) [$\bar{1}$01] to that of (111) [$\bar{1}$01], the higher the peak temperature. The peak temperatures were increased by the precipitation of y particles for the samples of all orientations. Electron microscopy of deformation induced dislocation arrangements under peak temperature has revealed that most of dislocations are straight screw dislocations. The mobility of screw dislocations decreases with increasing temperature. Above the peak temperature, dislocations begin to cross slip from the (111) [$\bar{1}$01] slip system to the (010) [$\bar{1}$01] slip system, thus decreasing the strength.

• Journal of Magnetics
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• 제9권4호
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• pp.116-120
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• 2004

Hexagonal barium-ferrite ($BaFe_{12}O_{19}$, magnetoplumbite structure; BaM) film with perpendicularly c-axis orientation was successfully deposited on (100) silicon substrates with an MgO (111) underlayer by rf diode sputtering and in-situ heating at $920^{\circ}C$. The magnetic and structural properties of 0.27 ${\mu}m$ thick BaM films on MgO (111) underlayers were compared to films of the same thickness deposited onto single-crystal MgO (111) and c-plane ($000{\ell}$) sapphire ($Al_2O_3$) substrates by vibrating sample magnetometry (VSM), x-ray diffractometer (XRD), and atomic force microscopy (AFM). The thickness dependence of MgO (111) underlayers on silicon wafer was found to have a large effect on both magnetic and structural properties of the BaM film. The thickness of 15 nm MgO (111) underlayers produced BaM films with almost identical magnetic and structural properties as the single-crystal substrates; this can be explained by the lower surface roughness for thinner underlayer thicknesses. The magnetization saturation ($M_s$) and the ratio $H_{cII}/H_{c{\bot}}$ for the BaM film with a 15 nm MgO (111) underlayer is 217 emu/cc and 0.24, respectively. This is similar to the results for the BaM films deposited on the single-crystal MgO (111) and sapphire substrates of 197 emu/cc and 0.10, 200 emu/cc and 0.12, respectively. Therefore, the proposed MgO (111) underlayer can be used in many applications to promote c-axis orientation without the cost of expensive substrates.

• 한국유통학회지:유통연구
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• 제16권1호
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• pp.65-93
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• 2011

본 연구에서는 관리형 유통경로의 구조적 요인들인 공급자 특유투자, 커뮤니케이션, 소매상 의존도가 신뢰에 미치는 효과를 검토하고자 하였다. 또한 이러한 변수들에 대한 관계수명주기의 조절효과를 밝히고자 하였다. 관계적 거래는 하루아침에 성사되는 것이 아니라 장기간에 걸친 반복적 거래 및 사회적 맥락(social context)이 누적된 결과로 발생하기 때문에 관계마케팅을 성공적으로 수행하기 위해서는 관계수명주기에 대한 단계별 검토가 우선되어야 한다. 작물보호제 소매상 296명으로부터 설문자료를 수집하여 분석한 결과, 공급자에 대한 소매상의 의존도가 신뢰를 가장 크게 증가시키는 것으로 나타났다. 특히 관계가 발전할수록 의존도의 영향력은 점점 더 커졌다. 따라서 공급자는 차별화된 제품과 서비스를 제공하여 시간의 흐름에 따라 소매상의 의존도가 더욱 높아질 수 있도록 노력해야 한다. 그리고 공급자 특유투자는 관계 초반에 신뢰를 증가시키는 역할을 하는 것으로 나타났다. 반면에 성숙기 이후에는 유의한 영향력을 보여주지 않았다. 이는 관계 초기에는 상대방을 평가하는 단서가 특유투자에 불과하기 때문에 특유투자의 효과가 크게 나타나지만 관계가 발전하면 상대방을 평가할 수 있는 여러 가지의 단서를 획득하게 되어 특유투자의 효과가 적은 것으로 볼 수 있다. 또한 양자간의 커뮤니케이션은 신뢰를 높여주는 것으로 나타났으며 신뢰는 장기지향성에 긍정적인 영향을 미치는 것으로 나타났다. 성숙기보다 강화기에서 커뮤니케이션의 영향력은 더 크게 나타났다. 본 연구는 관리형 시스템의 관계변수인 공급자 특유투자, 소매상 의존도, 양자 간 커뮤니케이션을 통합적으로 검토하였다는 점에서 의의를 찾을 수 있다. 그리고 관계수명주기의 조절효과를 검토함으로써 관계의 발전단계에 따른 차별적 전략을 제안할 수 있었다.

• Composites Research
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• 제34권2호
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• pp.77-81
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• 2021

복합재료의 높은 비강도와 비강성으로 인해 복합재료는 다양한 산업분야에서 광범위하게 사용되고 있다. 특히, 탄소 섬유 강화 복합재는 많은 기계적인 구조물에 널리 사용된다. 또한 이방성 특성을 갖는 탄소 섬유 강화복합재는 금속 재료와 달리 섬유 방향에 따라 피로 거동을 이해하는 것은 구조 설계에 있어서 매우 중요하다. 따라서 본 논문에서는 비낌 축(off-axis) 시편에 따라 복합재료의 피로 수명에 미치는 영향을 실험적으로 평가하였다. 이를 위해 복합재료의 비낌 축 시편(0°, 10°, 30°, 45°, 60°, 90°)에 대해 인장 및 피로 시험을 수행하였다. 피로 시험 결과, 복합재의 피로 강도는 섬유 방향이 0도로부터 조금 벗어날수록 피로 강도가 크게 감소하였으며 많이 벗어날수록 적게 감소하였다. 이는 적층 각이 커질수록 섬유의 하중을 지지하는 역할이 감소했기 때문이다. 또한 복합재의 피로 선도에 비낌 축 각도를 평준화하는 피로 강도 비율을 도입하여 피로 수명의 경향을 분석하였다. 피로강도 비율(Ψ)-피로 수명 선도를 이용하여 적층 각도와 관계없이 피로 수명을 단일선으로 표현하였다. 피로 강도비율을 통해 평준화된 피로 선도를 이용하면 2개 이상의 비낌 축 각도를 가지는 복합재의 피로 선도만으로도 임의의 다른 비낌 축 각을 가진 동일한 복합재의 피로 수명 곡선의 도출이 가능하다.

• Journal of Photoscience
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• 제9권2호
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• pp.379-381
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• 2002

The major electron transfer cofactors in photosystem II have been studied by pulsed EPR, pulsed electron electron double resonance (PELDOR) and laser excited spin polarized electron spin echo envelope modulation (ESEEM) methods, in non-oriented and oriented photosystem II membranes. Distances between radical pairs were determined trom the observed dipole interaction constants to be 27.3 A for P680-QA, 30 A, etc. with the error within 1 A. Angles between the distance vector and membrane normal was determined by orientation dependence of oriented membranes with the accuracy of 5˚ The results were compared with the recent structural data by X-ray analysis.

• Journal of Magnetics
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• 제7권3호
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• pp.94-97
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• 2002

The dependence on nickel oxide thickness and a ferromagnetic layer thickness in unidirectional and isotropic exchange-coupled NiO/NiFe(Fe) bilayer films was investigated by magnetic force microscopy to better understand the relation between magnetic domain structure and exchange biasing at microscopic length scales. As the NiO thickness increased, the domain structure of unidirectional biased films formed smaller and more complex in-plane domains. By contrast, for the isotropically coupled films, large domains generally formed with increasing NiO thickness including a cross type domain with out-of plane magnetization orientation. The density of the cross domain is proportional to exchange biasing field, and the fact that the domain mainly originated from the strongest exchange coupled region was confirmed by imaging in an applied external field during a magnetization cycle.