• 한국산학기술학회논문지
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• 제3권3호
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• pp.161-165
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• 2002

게르마늄첨가 다성분계 산화물 유리를 제조하여 자외선(UV) 조사에 따른 유리의 미세 구조변화를 PL(photo-luminescence)과 ESR(electron spin resonance)을 이용하여 관찰하였다. 게르마늄 첨가량이 증가함에 따라 PL방사량은 증가하였으며, UV 조사 후에는 처음과 반대되는 광혹화 현상으로 감소하는 현상을 나타냈다. UV조사로 변화된 특성은 열처리를 통하여 회복이 가능하였으며, ESR 측정에서도 PL결과와 같은 광혹화 현상(phodarkenine effect)과 열표백화 현상(thermal bleaching effect)이 확인되었다. 또한, XRD 분석을 통하여 이러한 현상이 비정질 상은 그대로 유지하는 미세구조 변화임을 알 수 있었다.

• Journal of the Optical Society of Korea
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• 제18권1호
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• pp.45-49
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• 2014

Well-crystallized $BaSi_2O_5:Eu^{2+}$ phosphor films were synthesized by heat treatment of spin-coated BaO:Eu on $SiO_2$ glass. We investigated luminescence-structure properties of these phosphor films as a function of heat-treatment temperature. From x-ray diffraction patterns, our $BaSi_2O_5:Eu^{2+}$ phosphor films revealed that (111)- and (204)-crystal planes of $BaSi_2O_5$ crystal were dominantly increased with an increase of heat-treatment temperature. Photoluminescence intensities of $BaSi_2O_5:Eu^{2+}$ phosphor films were increased with amount of these crystal planes. It can be explained that $Eu^{2+}$ ions were stably occupied at specific crystal orientation of $BaSi_2O_5$ crystal, enhancing the luminescent intensities of $BaSi_2O_5:Eu^{2+}$ phosphor films. In addition, our $BaSi_2O_5:Eu^{2+}$ phosphor films had transmittance of 70% at 510 nm,.due to the dense morphology and specific crystallinity of $BaSi_2O_5:Eu^{2+}$ phosphor films.

• Bulletin of the Korean Chemical Society
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• 제18권10호
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• pp.1105-1108
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• 1997

The new amorphous intermetallic compounds, M3(AsTe3)2: M=Cr, Co, Fe, were synthesized by the precipitation reaction of the Zintl anion AsTe33- with the divalent transition metal halides in aqueous solution and analyzed by EDS equipped with SEM and PIXE. The empirical formula of the specimens was found to be Fe3.0As1.8Te5.9, Co3.0As2.1Te6.5, and Cr3.0As2.0Te6.9 by the quantitative elemental analysis. The dc specific resistivity of the materials was measured as a function of temperature in the range from 20 to 300 K, in which their resistivity of Cr3(AsTe3)2 was largely dependent on temperature, while those of Co3(AsTe3)2 and Fe3(AsTe3)2 were only slightly dependent on temperature. To characterize the spin glass state of the specimens, the ac and dc magnetic susceptibility were measured and it was found that Co3(AsTe3)2 and Fe3(AsTe3)2 undergo a transition to a spin glass state at 6 K and 38 K, respectively. Magnetization data are reported as both thermal remanent magnetization (TRM) and isothermal remanent magnetization (IRM) as a function of magnetizing field and temperature.

• Journal of Magnetics
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• 제4권1호
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• pp.33-37
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• 1999

Unidirectional magnetic anisotropy field ($H_an$) was investigated for thin films of $CdCr{2-2x}In_{2X}Se_4 (0$\leq$x$\leq$0.2). This anisotropy originates from the microscopic anisotropic Dzyaloshinskii-Moriya (DM) interaction which arise from the spin-orbit scattering of the conduction electrons by the nonmagnetic impurities. This interaction maintains the remanent magnetization in the direction of the initial applied field. Then the single easy direction of the magnetization is parallel to the direction of the magnetic field. The anisotropy produced by field cooling is unidirectional I.e. the spins system deeps some memory of the cooling field direction. The chalcogenide spinel of$ CdCr_{2-2x}In){2X}Se_4$belongs to the class of the magnetic semiconductors. The magnetic disordered state is obtained when ferromagnetic structure is diluted by In. Then we have the mixed phase characterised by coexistence the magnetic long range ordering (IFN-infinite ferromagnetic network) and the spin glass order (Fc-finite clusters). The total magnetic anisotropy energy depends on the state of magnetic ordering. In our study we concentrated on the magnetic state with reentrant transition and spin glass state. The polycrystalline $ CdCr_{2-2x}In){2X}Se_4$ thin films were obtained by rf sputtering technique. We applied the ferromagnetic resonance (FMR) and M-H loop techniques for determining the temperature composition dependencies of Han. From the experimental data, we have found that Han decreases almost linearly when temperature is increased and in the low temperature is about three times bigger at SG state with comparison to the state with REE.

• Journal of Information Display
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• 제9권3호
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• pp.8-11
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• 2008

A novel non-alkoxide sol-gel process for synthesizing Ga-doped ZnO thin film on glass was derived for possible use as a transparent electrode in flat-panel displays, using zinc acetate dehydrate as the starting material. The structural and electrical properties of thin films have been characterized as functions of Ga addition and post-heat-treatments. Their carrier density, Hall mobility, and optical transmittance were measured and discussed herein to explain the characteristics of the sol-gel-derived Ga-doped ZnO thin film on glass.

• 통합자연과학논문집
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• 제6권4호
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• pp.211-214
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• 2013

In this study, in order to investigate how consecutive treatments of glass surface with HF acid and water vapor/Ar plasma affect the quality of 3-aminopropyltriethoxysilane self-assembled monolayer (APS-SAM), poly(3,4-ethylenedioxythiophene) (PEDOT) thin films were vapor phase-polymerized immediately after spin coating of FeCl3 and poly-urethane diol-mixed oxidant solution on the monolayer surfaces prepared at various treatment conditions. For the film characterization, various poweful tools were used, e.g., FE-SEM, an optical microscope, four point probe, and a contact angle analyzer. The characterization revealed that HF treatment is not desirable for the synthesis of a high quality PEDOT thin film via vapor phase polymerization method. Rather, sole treatment with plasma noticeably improved the quality of APS-SAM on glass surface. As a result, a highly dense and smooth PEDOT thin film was grown on uniform oxidant film-coated APS monolayer surface.

• 통합자연과학논문집
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• 제6권4호
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• pp.215-219
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• 2013

In this study, in order to investigate how consecutive treatments of glass surface with HF acid and water vapor/Ar plasma affect the quality of 3-aminopropyltriethoxysilane self-assembled monolayer (APS-SAM), poly(3,4-ethylenedioxythiophene) (PEDOT) thin films were vapor phase-polymerized immediately after spin coating of FeCl3 and poly-urethane diol-mixed oxidant solution on the monolayer surfaces prepared at various treatment conditions. For the film characterization, various poweful tools were used, e.g., FE-SEM, an optical microscope, four point probe, and a contact angle analyzer. The characterization revealed that a well prepared APS-SAM on a glass surface treated with water vapor/Ar plasma is very useful for uniform coating of FeCl3 and DUDO mixed oxidant solution, regardless of HF treatment. On the other hand, a bare glass surface without APS-SAM but treated with HF and water vapor/Ar plasma generally led to a very poor oxidant film. As a result, PEDOT films vapor phase-polymerized on APS-SAM surfaces are far superior to those on bare glass surfaces in the quality and electrical characteristics aspects.

• 한국자기학회지
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• 제27권4호
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• pp.123-128
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• 2017

PtMn계 스핀밸브(Spin Valve, SV) 다층박막의 하부층 구조를 달리하여 제작된 시료를 열처리 후 측정한 자기저항(magnetoresistance, MR) 곡선과 자기이력 곡선(MH loop)으로부터 얻은 등방성의 자기적 특성을 조사하였다. PtMn층이 없는 스핀밸브 구조의 Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/Ta(4 nm) 다층박막으로 측정한 MR 곡선에서 얻은 교환결합력($H_{ex}$), 보자력($H_c$), 자기저항비(MR(%))는 각각 0 Oe, 약 25 Oe, 3.3 %이었다. Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/PtMn(6 nm)/Ta(4 nm) 다층박막으로 측정한 MR 곡선에서 반강자성체인 PtMn 박막으로 나타낸 효과로 하여금 나비 날개 형태로 얻은 $H_{ex}$, $H_c$, MR(%)는 각각 2 Oe, 316 Oe, 4.4 %이었다. 반강자성체인 PtMn층이 중간층으로 삽입된 이중 GMR-SV 다층박막으로 측정한 MR 곡선과 MH loop에서 얻은 $H_c$는 각각 37.5 Oe과 386 Oe이었으며, MR(%)는 각각 3.5 %와 6.5 %로 2개의 히스테리시스에서 사각비가 뚜렷하게 대칭적으로 나눠져 자기적 특성을 나타내었다. PtMn계 CoFe 스핀밸브 박막의 매우 작은 $H_{ex}$ 값과 미미한 형상이방성을 갖는 효과로 하여금 비등방성을 갖는 자기적 특성을 잃게 되었다. 이러한 결과는 PtMn 박막의 하부층과 상부층에 있는 SV 다층박막에서 각 강자성체의 자화 스핀배열로 일어나는 효과를 나타내었다.

• 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.

• 한국자기학회지
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• 제8권6호
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• pp.362-368
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• 1998

반강자성 Cr86Al14계 스핀밸브막의 자기특성과 내열 내식성에 대해 연구하엿다. Cr86Al14스핀밸브막의 자기적성질은 강자성층, 자성층 및 비자성층두께에 의존하였으며, glass/Cr86Al14(600$\AA$)/Ni81Fe19(50$\AA$)/Cu(40$\AA$)/Ni81Fe19(40$\AA$)구조에서의 교환결합자장(Hex)은 20 Oe, 자기저항비(MR ratio (%))는 2%를 나타내었다. Cr96Al14 및 Fe50Mn50 스핀밸브막은 annealing온도가 증가함에 따라 모두 Hex 및 MR비가 감소하는 경향을 나타내엇으나 FeMn막에 비해 CrAl막이 우수하여, FeMn막은 15$0^{\circ}C$, CrAl막은 25$0^{\circ}C$에서 Hex 및 MR비값을 상실하였다. 또한 가혹한 환경에서의 스핀밸브막의 부식저항성을 평가하고자 35$^{\circ}C$,90% 습도상태의 챔버내에서 Hex와 MR비값의 변화를 관찰한 결과 CrAl막의 경우에는 Hex 및 MR비 값이 시간이 경과해는 변화지 않았으나, FeMn막은 15일정도 경과하자 거의 상실하는 결과를 나타냈다. SEM관찰결과 FeMn막은 pitting이 나타났으며 15일정도 경과후에는 박리가 발생하였다.