• 한국자기학회지
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• 제9권1호
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• pp.41-47
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• 1999

DC magnetron sputtering 방법으로 Corning glass 기판 위에 기저층을 Cr과 Ta로 바꾸어가면서 보자력이 다른 Ni81Fe19와 CoFe(Co)를 이용하여 buffer;[FeNi/Cu/CoFe(Co)/Cu]N의 형태로 spin-valve 다층박막을 제작하여 자기저항비의 기저층 종류와 두께, 비자성층 Cu층 두께, 연자성층 NiFe층 두께, 사이층 박막 반복 적층횟수, 기판온도 및 열처리 온도 의존성을 조사하였다. 제작된 시료의 자기저항비는 4탐침법으로 측정하였으며 이들의 구조, 자기적 성질을 조사하기 위해 X-선 회절분석, 시료진동형 자기계(VSM) 분석을 하였다. Cr기저층 두께가 50$\AA$, Cu 두께 50$\AA$, NiFe 및 Co 두께가 각각 20$\AA$이며 사이층 박막 반복 적층횟수 10인 경우에 기판온도가 9$0^{\circ}C$일 때 극대 자기저항비 및 보자력은 각각 7.5% 및 140 Oe를 보이다가 기판온도 상승에 따라 감소하였다. 자기장 감응도(MR slope)는 열처리 온도 15$0^{\circ}C$까지는 0.25%/Oe을 유지하다가 20$0^{\circ}C$에서는 0.03%/Oe로 감소하였으며 열안정성을 결정하는 주요한 요인은 NiFe 자성층의 연자기 특성 저하라는 것을 확인할 수 있었다.

• Nano
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• 제13권11호
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• pp.1850125.1-1850125.12
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• 2018

To reduce the imbalance of impedance matching between the magnetic metal nanowires and free space, $Fe/TiO_2$ core/shell nanowire arrays with different diameters were fabricated in the templates of anodic aluminum oxide membranes by electrodeposition. The influences of the microstructure on the microwave absorption properties of the $Fe/TiO_2/Al_2O_3$ composites were studied by the transmission/reflection waveguide method. It was demonstrated experimentally that both the interfacial polarization and the diameter of the $Fe/TiO_2$ core/shell nanowires have critical effects on the microwave absorption properties. We also investigated the angle dependence of the microwave absorption properties. Due to the interfacial polarization and associated relaxation, the $Fe/TiO_2/Al_2O_3$ composites exhibited optimal microwave absorption properties when microwave propagation direction was accordant with the axis of the nanowires. Finally, we managed to obtain an optimal reflection loss of below -10 dB (90% absorption) over 10.2-14.8 GHz, with a thickness of 3.0 mm and the minimum value of -39.4 dB at 11.7 GHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.230-233
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• 2004

The stochiometric mix of evaporating materials for the $CuInS_2$ single crystal thin films was prepared from horizontal furnance. Using extrapolation method of X-ray diffraction patterns for the $CuInS_2$ polycrystal, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were $5.524\;{\AA}$ and $11.142\;{\AA}$, respectively. To obtain the single crystal thin films, $CuInS_2$ mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the hot wall epitaxy (HWE) system. The source and substrate temperature were 640 t and 430 t, respectively and the thickness of the single crystal thin films was $2{\mu}m$. Hall effect on this sample was measured by the method of van dot Pauw and studied on carrier density and temperature dependence of mobility. The carrier density and mobility deduced from Hall data are $9.64{\times}10^{22}/m^3,\;2.95{\times}10^{-2}\;m^2/V{\cdot}s$ at 293 K, respectively The optical energy gaps were found to be 1.53 eV at room temperature. From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the thin film, we have found that the values of spin orbit coupling splitting ${\Delta}So$ and the crystal field splitting ${\Delta}Cr$ were 0.0211 eV and 0.0045 eV at 10 K, respectively. From PL peaks measured at 10K, 807.7nm (1.5350ev) mean Ex peak of the free exciton emission, also 810.3nm (1.5301eV) expresses $I_2$ peak of donor-bound exciton emission and 815.6nm (1.5201eV) emerges $I_1$ peak of acceptor-bound exciton emission. In addition, the peak observed at 862.0nm (1.4383eV) was analyzed to be PL peak due to donor-acceptor pair(DAP).

• 한국초전도ㆍ저온공학회논문지
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• 제15권4호
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• pp.15-20
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• 2013

We investigated the flux pinning properties of both 10 mol% Zr-and Sn-doped $YBa_2Cu_3O_{7-{\delta}}$ (YBCO) films with the same thickness of ~350 nm for a comparative purpose. The films were prepared on the $SrTiO_3$ (STO) single crystal substrate by the metal-organic deposition (MOD) process. Compared with Sn-doped YBCO film, Zr-doped one exhibited a significant enhancement in the critical current density ($J_c$) and pinning force density ($F_p$). The anisotropic $J_{c,min}/J_{c,max}$ ratio in the field-angle dependence of $J_c$ at 77 K for 1 T was also improved from 0.23 for Sn-doped YBCO to 0.39 for Zr-doped YBCO. Thus, the highest magnetic $J_c$ values of 9.0 and $2.9MA/cm^2$ with the maximum $F_p$ ($F_{p,max}$) values of 19 and $5GN/m^3$ at 65 and 77 K for H // c, respectively, could be achieved from Zr-doped YBCO film. The stronger pinning effect in Zr-doped YBCO film is attributable to smaller $BaZrO_3$ (BZO) nanoparticles (the average size ${\approx}28.4$ nm) than $YBa_2SnO_{5.5}$ (YBSO) nanoparticles (the average size ${\approx}45.0$ nm) incorporated in Sn-doped YBCO film since smaller nanoparticles can generate more defects acting as effective flux pinning sites due to larger incoherent interfacial area for the same doping concentration.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1229-1232
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• 1994

The purpose of this study is to research and develop solid polymer electrolyte(SPE) for Li secondary battery. This paper describes the effects of lithium salts, plasticizer addition and temperature dependence of conductivity of PEO electrolytes. Polyethylene oxide(PEO) based polymer electrolyte films were prepared by solution casting an acetonitrile solution of preweighed PEO and Li salt. After solvent evaporation, the electrolyte films were vacuum-dried at $60^{\circ}C$ for 48h, the thickness of the films were $90{\sim}110{\mu}m$. The conductivity properties of prepared PEO electrolytes are summarized as follows. PEO electrolyte complexed with $LiClO_4$ shows the better conductivity of the others. $PEO-LiClO_4$ electrolyte when $EO/Li^+$ ratio is 8, showed the best conductivity. Optimum operating temperature of PEO electrolyte is $60^{\circ}C$. By adding propylene carbonate and ethylene carbonate to $PEO-LiClO_4$ electrolyte, its conductivity was higher than $PEO-LiClO_4$ without those. Also $PEO_8LiClO_4$ electrolyte remains static up to 4.5V vs. $Li/Li^+$.

• Advances in materials Research
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• 제1권1호
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• pp.51-74
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• 2012

A powder metallurgy-based rapid consolidation technique, Plasma Pressure Compaction ($P^2C^{(R)}$), was utilized to produce near-net shape parts of gamma titanium aluminides (${\gamma}$-TiAl). Micron-sized ${\gamma}$-TiAl powders, composed of Ti-50%Al and Ti-48%Al-2%Cr-2%Nb (at%), were rapidly consolidated to form near-net shape ${\gamma}$-TiAl parts in the form of 1.0" (25.4 mm) diameter discs, as well as $3"{\times}2.25"$ ($76.2mm{\times}57.2mm$) tiles, having a thickness of 0.25" (6.35 mm). The ${\gamma}$-TiAl parts were consolidated to near theoretical density. The microstructural morphology of the consolidated parts was found to vary with consolidation conditions. Mechanical properties exhibited a strong dependence on microstructural morphology and grain size. Because of the rapid consolidation process used here, grain growth during consolidation was minimal, which in turn led to enhanced mechanical properties. Consolidated ${\gamma}$-TiAl samples corresponding to Ti-48%Al-2%Cr-2%Nb composition with a duplex microstructure (with an average grain size of $5{\mu}m$) exhibited superior mechanical properties. Flexural strength, ductility, elastic modulus and fracture toughness for these samples were as high as 1238 MPa, 2.3%, 154.58 GPa and 17.95 MPa $m^{1/2}$, respectively. The high temperature mechanical properties of the consolidated ${\gamma}$-TiAl samples were characterized in air and vacuum and were found to retain flexural strength and elastic modulus for temperatures up to $700^{\circ}C$. At high temperatures, the flexural strength of ${\gamma}$-TiAl samples with Ti-50%Al composition deteriorated in air by 10% as compared to that in vacuum. ${\gamma}$-TiAl samples with Ti-48%Al-2%Nb-2%Cr composition exhibited better if not equal flexural strength in air than in vacuum at high temperatures.

• 폴리머
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• 제33권5호
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• pp.485-489
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• 2009

중수소화 폴리스티렌-폴리에틸렌옥사이드 이중블록공중합체(dPS-PEO)로 형성된 미셀의 구조에 대한 온도 의존성을 소각중성자산란(SANS)을 이용하여 조사하였다. SANS 데이터는 코어-쉘 모델의 form factor와 hard-sphere structure factor를 결합하여 분석하였으며, 산란 곡선 맞춤을 이용하여 미셀 응집수와 코로나 반경을 구하였다. 온도가 $25^{\circ}C$에서 $45^{\circ}C$로 증가함에 따라서 미셀 응집수는 229에서 240으로 변화하였으며, 이로 인해 코어 반경이 증가하였다. 그러나, 미셀의 쉘 두께는 6.2 nm에서 5.8 nm로 감소하였다. 이러한 구조적 변화는 온도 증가에 따라서 PEO 블록의 소수성이 증가함으로써 코로나 내의 친수성 그룹 당 수화 부피가 감소하였기 때문이다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집
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• pp.273-280
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• 2002

The stochiometric mix of evaporating materials for the CuGaTe$_2$ single crystal thin films was prepared from horizontal furnance. For extrapolation method of X-ray diffraction patterns for the CuGaTe$_2$ polycrystal, it was found tetragonal structure whose lattice constant a$\_$0/ and c$\_$0/ were 6.025 ${\AA}$ and 11.931 ${\AA}$, respectively. To obtain the single crystal thin films, CuGaTe$_2$ mixed crystal was deposited on throughly etched semi-insulator GaAs(100) substrate by the Hot Wall Epitaxy (HWE) system. The source and substrate temperature were 670 $^{\circ}C$ and 410 $^{\circ}C$ respective1y, and the thickness of the single crystal thin films is 2.1 $\mu\textrm{m}$. The crystalline structure of single crystalthin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of van der Pauw and studied on carrier density and mobility dependence on temperature. The carrier density and mobility of CuGaTe$_2$ single crystal thin films deduced from Hall data are 8.72${\times}$10$\^$23/㎥, 3.42${\times}$10$\^$-2/㎡/V$.$s at 293K, respectively. From the photocurrent spectrum by illumination of perpendicular light on the c - axis of the CuGaTe$_2$ single crystal thin film, we have found that the values of spin orbit coupling Δs.o and the crystal field splitting Δcr were 0.0791 eV and 0/2463eV at 10K, respectively. From the PL spectra at 10K, the peaks corresponding to free bound excitons and D-A pair and a broad emission band due to SA is identified. The binding energy of the free excitons are determined to be 0.0470eV and the dissipation energy of the donor -bound exciton and acceptor-bound exciton to be 0.0490eV, 0.00558eV, respectively.

• 한국재료학회지
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• 제19권2호
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• pp.73-78
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• 2009

This study investigated the dependence of the various sputtering conditions (Ar pressure: $2{\sim}10\;mTorr$, Power: $50{\sim}150\;W$) and thickness ($50{\sim}1200\;nm$) of Si thin film on the electrochemical properties, microstructural properties and the capacity fading of a Si thin film anode. A Si layer and a Ti buffer layer were deposited on Copper foil by RF-magnetron sputtering. At 10 mTorr, the 50 W sample showed the best capacity of 3323 mAh/g, while the 100 W sample showed the best capacity retention of 91.7%, also at 10 mTorr. The initial capacities and capacity retention in the samples apart from the 50W sample at 10 mTorr were enhanced as the Ar pressure and power increased. This was considered to be related to the change of the microstructure and the surface morphology by various sputtering conditions. In addition, thinner Si film anodes showed better cycling performance. This phenomenon is caused by the structural stress and peeling off of the Si layer by the high volume change of Si during the charge/discharge process.

• 한국재료학회지
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• 제5권6호
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• pp.715-722
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• 1995

Vlnylbenzyl triphenyl phosphonim chloride (VTPC) 단량체를 감습막으로 사용하기 위하여 합성하였다. 감습막 성분은 서로 다른 조성의 VTPC와 스티렌의 공중합체(VTPC : ST=1 : 0, 7 : 3, 1 : 1, 3 : 7)들이며 감습막의 상대 습도 변화에 대한 전기적 성질의 변화를 측정하였다. 임퍼던스는 감습막중 VTPC의 함량이 증가할수록 감소하였으며, 또한 전극위에 도포한 감습막의 두께가 증가하면 임퍼던스 역시 감소하였다. 감습막중 VTPC와 ST의 성분비가 1대 1인 감습막의 임피던스는 상대습도 70~90%RH 범위에서 12M$\Omega$에서 100K$\Omega$ 사이에서 변하였으며 고습이나 결로를 감지할 수 있는 센서로서 응용이 가능하였다. 15$^{\circ}C$~35$^{\circ}C$범위에서의 은도 의존상수는 -0.5%RH/$^{\circ}C$이었으며 히스테리시스는 $\pm$2%RH의 범위 안에서 나타났다. 응답속도는 상대습도가 75%RH에서 95RH%까지 또는 역으로 변화할 때 40초이었다.