• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.136-136
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• 2010

$Ge_2Sb_2Te_5$ (GST)는 광학 스토리지 및 PRAM(Phase-change Random Access Memory)에 적용 가능한 대표적인 상변화 물질이며 상변화 거동에 대한 다양한 연구가 진행되고 있다. 차세대 비휘발성 메모리로 각광을 받고 있는 PRAM의 경우 저전력 그러나 향후 고집적, 고성능 PRAM 소자구현을 위해서는 Reset 전류 감소를 통한 소비 전력 감소, 인접 셀간의 'cross talking'을 방지할 수 있는 열적 안정성 개선 등의 문제점들을 해결해야 한다. GST 물질의 전기적, 열적 특성을 조절하여 이러한 문제를 해결하기 위하여 GST 물질에 이종의 원소를 첨가하는 연구가 활발히 진행되고 있으며, 특히 질소 첨가에 의해 결정 성장 억제를 통한 결정화 온도 증가, 결정질의 저항 증가 등의 보고가 있었다. 본 연구에서는 질소를 첨가한 N-doped $Ge_2Sb_2Te_5$ (NGST) 박막의 상변화 거동을 규명하고 GST 박막과 비교하여 첨가된 질소의 영향을 분석하고자 한다. D.C Magnetron sputtering 방법으로 증착된 GST와 NGST 박막을 등온으로 유지하여 각 온도별로 열처리 시간 증가에 따른 비저항을 실시간으로 측정하여 GST와 NGST 박막의 상분율을 계산하고 Kissinger 모델을 이용하여 effective activation energy ($E_a$)를 구하였다. GST와 NGST 박막의 $E_a$는 각각 $2.08\;{\pm}\;0.11\;eV$와 $2.66\;{\pm}\;0.12\;eV$로 계산되었다. 따라서 첨가된 질소에 의해 NGST 박막의 결정화를 위하여 GST 박막의 경우보다 더 큰 활성화 에너지가 필요하다.

• 한국재료학회지
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• 제7권6호
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• pp.510-516
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• 1997

반응성RF 마그네트론 스퍼터링 법으로 상온에서 c-축으로 우선 배향된 AIN 박막을 여러 기판 위에 증착하였다. SiO$_{2}$/Si, Si$_{3}$N $_{4}$Si, Si(100), Si(111)그리고 $\alpha$-AI$_{2}$O$_{3}$(0001) 기판에서 AIN(0002)로킹커브 피크의 표준편차는 각각 2.6˚, 3.1˚2.6˚, 2.5˚ 그리고 2.1˚ 의 값을 나타내었다. $\alpha$-AI$_{2}$O$_{3}$(0001) 기판에 증착된 AIN박막은 epitaxial 성장을 나타내었다. Si기판에 증착된 AIN박막에서 측정된 비저항과 1MHz 주파수에서 측정된 유전상수의 값은 각각 $10^{11}$Ωcm와 9.5였다. IDT/AIN/$\alpha$-AI$_{2}$O$_{3}$(0001)구저를 갖는 지연선 소자의 표면 탄성과 특성을 측정하였다. 상 속도, 전기기계 결합계수 그리고 전파손실은 H/λ가 0.17-0.5 범위에서 각각 5448-5640m/s, 0.13-0.17% 그리고 0.41-0.64dB/λ의 값을 나타내었다.다.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.340-340
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• 2002

In an effort to develop alternative single buffer layer technology for YBa$_2$Cu$_3$O$_{7-{\delta}}$ (YBCO) coated conductors, we have investigated both LaMnO$_3$, (LMO) and La$_2$Zr$_2$O$_{7}$ (LZO) as potential buffer layers. High-quality LMO films were grown directly on textured Ni and Ni-W (3%) substrates using rf magnetron sputtering. Highly textured LZO buffers were grown on textured Ni substrates using sol-gel alkoxide processing route. YBCO films were then grown on both LMO and LZO buffers using pulsed laser deposition. Detailed X-ray studies have shown that YBCO films were grown on both LMO and LZO layers with a single epitaxial orientation. A high J$_{c}$ of over 1 MA/cm$^2$ at 77 K and self-field was obtained on YBCO films grown on both LMO-buffered Ni or Ni-W substrates, and also on LZO-buffered Ni substrates. We have identified LaMnO$_3$ as a good diffusion barrier layer for Ni and it also provides a good template for growing high current density YBCO films. Similarly we have also demonstrated the growth of high J$_{c}$ YBCO films on all solution buffers. We will discuss in detail about our buffer deposition processes. processes.s.s.s.s.

• 한국세라믹학회지
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• 제32권7호
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• pp.761-768
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• 1995

Double layered BaTiO3 thin films with high dielectric constant as well as good insulating property were prepared for the application to low voltage driving thin film electroluminescent (TFEL) device. BaTiO3 thin films were formed by rf-magnetron sputtering technique. Amorphous and polycrystalline BaTiO3 thin films were deposited at the substrate temperatures of room temperature and 55$0^{\circ}C$, respectively. Two kinds of films prepared under these conditions showed high resistivity and high dielectric constant. The figure of merit (=$\varepsilon$r$\times$Eb.d) of polycrystalline BaTiO3 thin film was very high (8.43$\mu$C/$\textrm{cm}^2$). The polycrystalline BaTiO3 showed a substantial amount of leakage current (I), under the high electric field above 0.5 MV/cm. The double layered BaTiO3 thin film, i.e., amorphous BaTiO3 layer coated polycrystalline BaTiO3 thin film, was prepared by the new stacking method and showed very good dielectric and insulating properties. It showed a high dielectric constant fo 95 and leakage current density of 25 nA/$\textrm{cm}^2$ (0.3MV/cm) with the figure of merit of 20$\mu$C/$\textrm{cm}^2$. The leakage current density in the double layered BaTiO3 was much smaller than that in polycrystalline BaTiO3 under the high electric field. The saturated brightness of the devices using double layered BaTiO3 was about 220cd/$m^2$. Threshold voltage of TFEL devices fabricated on double layered BaTiO3 decreased by 50V compared to the EL devices fabricated on amorphous BaTiO3.

• 한국결정성장학회지
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• 제9권5호
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• pp.486-492
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• 1999

본 실험에서는 D.C magnetron sputtering을 사용하여 Mn-Ir/Ni-Fe/buffer/Si 다층박막의 교환결합 자계와 보자력에 영향을 주는 인자를 미세구조의 관점에서 분석하였다. (111) 우선방위에 상관없이 모든 시편에서 155 Oe 이상의 교환결합 자계가 발생하였다. Mn-Ir/Ni-Fe 의 계면에서 Mn-Ir의 결정립 크기와 게면 거칠기가 Mn-Ir/Ni-Fe 다층박막의 교환결합 자계와 보자력에 가장 많은 영향을 주는 것을 알 수 있었다. Mn-Ir/Ni-Fe/Cu/Ni-Fe/buffer/Si spin-valve 다층박막에서 각 층의 두께와 하지층에 따른 자기저항비와 coulping field을 분석하였다. Mn-Ir(10 nm)/Ni-Fe(7.5 nm)/Cu(2 nm)Ni-Fe(6 nm)/Ta (5 nm)/Si에서 최대 자기저항비가 발생하였다. 강자성체의 결정립 크기가 거대자기저항비에 영향을 주는 것을 알 수 있었다. 그리고 계면 거칠기와 강자성체의 결정립 크기가 coulping field 에 많은 영향을 주는 것을 알 수 있었다.

• 한국표면공학회지
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• 제40권2호
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• pp.91-97
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• 2007

In this study we investigated the oxygen effect on the nucleation and its residual stress during unbalanced magnetron sputtering. Up to 0.5% in oxygen flow rate, cubic phase (c-BN) was dominated with extremely small fraction of Hexagonal phase (h-BN) of increasing trend with oxygen concentration, whereas hexagonal phase is dominated beyond 0.75% flow rate. Interestingly, the residual stress in cubic-phase-dominated films was substantially reduced with small amount of oxygen (${\sim}0.5%$) down to a low value comparable to the h-BN case. This may be because oxygen atoms break B-N $sp^3$ bonds and make B-O bonds more favorably, increasing $sp^2$ bonds preference, as revealed by FTIR and NEXAFS. It was confirmed by experimental facts that the threshold bias voltage for nucleation and growth of cubic phase were increased from -55 V to -70 V and from -50 V to -60 V respectively. The reduction of residual stress in O-added c-BN films is seemingly resulting from the microstructure of the films. The oxygen tends to increase slightly the amount of h-BN phase in the grain boundary of c-BN and the soft h-BN phase of 3D network including surrounding nano grains of cubic phase may relax the residual stress of cubic phase.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.453-453
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• 2010

In this study, zinc germanate ($Zn_2GeO_4$) thin films has been synthesized by using radio frequency magnetron sputtering and the divalent manganese-activated luminescence was characterized. X-ray diffraction patterns of the as-deposited $Zn_2GeO_4$:Mn films showed only a broad feature, indicative of an amorphous structure. Scanning electron microscopy images revealed that the as-deposited $Zn_2GeO_4$:Mn has a smooth surface morphology. The $Zn_2GeO_4$:Mn films were found to be crystallized by annealing in air ambient at temperatures as low as $700^{\circ}C$. The annealed $Zn_2GeO_4$:Mn possessed a rhombohedral polycrystalline structure. The broad-band photoluminescent emission spectrum from 470 to 650nm was obtained at room temperature from the $Zn_2GeO_4$:Mn films. The emission peak was centered at around 535nm in the green range, which originates from the intrashell transition of manganese $3d^5$ electrons from $^4T_1$ excited-state level to the $^6A_1$ ground state. The PL emission spectrum had an asymmetric line shape, which results from the $^3d_5$ electron transitions of divalent manganese ions located at different sites of the zinc germanate host crystal lattice. Electroluminescent devices were fabricated using $Zn_2GeO_4$:Mn as an emission layer. The fabricated devices showed a green EL emission similar to the PL emission. The CIE chromaticity color coordinates of the EL emission were determined to be x=0.308 and y=0.657.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 추계학술대회 논문집 전기물성,응용부문
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• pp.23-25
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• 2001

In this work, the $Ta_2O_5$ thin films were deposited on Pt/n-Si substrate by reactive magnetron sputtering and the RTA treatment at temperatures range from 650 to $750^{\circ}C$ in $O_2$ and vacuum. X-ray diffraction analysis, FE SEM, dielectric properties and leakage current density have been used to study the structural and electrical properties of the $Ta_2O_5$ thin films. XRD result showed that as- deposited films were amorphous and the annealed films crystallized (<$700^{\circ}C$) into ${\beta}-Ta_2O_5$. The crystallinity increased with temperature in terms of an increase in the intensity of the diffracted peaks(${\beta}-Ta_2O_5$) and annealing in oxygen reduced defect dang1ing Ta-O bonds. As deposited $Ta_2O_5$ films show the leakage current density $10^{-7}$ to $10^{-8}$ (A/$cm^2)$ at low electric fields (<200 kV/cm) However, it was found leakage current density of $Ta_2O_5$ thin films decreased with $O_2$ ambient annealing. The dielectric constant of the as deposited $Ta_2O_5$ thin films was ${\varepsilon}_r$ $9{\sim}11$ but the dielectric constant was increased after RTA treatment in $O_2$ ambient more then in vacuum.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.102-103
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• 2008

Magnetron Sputtering, MOCVD, Thermal Evaporation에 의해 성장된 ZnO layer에 대한 Dependency Temperature Photoluminescence (PL)를 이용하여 비교 분석을 통해 Deep level emission에 대해 연구하였다. Sputter에 의해 성장된 ZnO 박막은 Violet, Green, Orange-red 영역의 $Zn_i$, $V_o$, $O_i$의 defect에 의한 Deep level emission을 보였고, MOCVD에 의해 성장된 박막은 비교적 산소양이 낮은 성장 조건에서는 blue-green 영역에서, 산소양이 높은 조건에서의 박막은 Orange-red 영역의 Deep level emission을 보였다. Blue-green 영역에서의 emission은 온도가 증가함에 따라 다른 Barrier를 보였는데, 이는 $V_{Zn}$와 $V_o$에 의한 것임을 알 수 있었다. 한편, ZnO nanorods는 $V_o$에 의한 Green 영역에서의 Deep level emission을 보였다.

• 열처리공학회지
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• 제24권6호
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• pp.338-342
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• 2011

Ga doped ZnO (GZO) thin films were deposited with RF magnetron sputtering on glass substrate and then the effect of post deposition annealing at nitrogen atmosphere on the structural, optical and electrical properties of the films was investigated. The post deposition annealing process was conducted for 30 minutes at different temperature of 150, 300 and $450^{\circ}C$, respectively. As increase annealing temperature, GZO films show the increment of the prefer orientation of ZnO (002) diffraction peak in the XRD pattern and the optical transmittance in a visible wave region was also increased, while the electrical sheet resistance was decreased. The figure of merit obtained in this study means that GZO films which vacuum annealed at $450^{\circ}C$ have the highest optoelectrical performance in this study.