• Title/Summary/Keyword: epitaxial film

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A Possible Origin of Ferromagnetism in Epitaxial BiFeO3 thin Films

  • Chang, Jae-wan;Jang, Hyun M.;Kim, Sang-Koog
    • Journal of Magnetics
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    • v.11 no.3
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    • pp.108-110
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    • 2006
  • We successfully enhanced the performance of a spin valve by inserting an ultra-thin layer of partially oxidized Fe in the pinned and free layers. With the exchange bias field kept large, the spin valve reached a GMR of 12%, which corresponded to a 55% increase in GMR when we compared it with that of spin valves without any inserted layer. The layer of partially oxidized Fe was more effective for improving the properties of the spin valve than the layer of partially oxidized $Co_{90}Fe_{10}$. Considering all the results, we can contribute the significant improvement to the combined effect of the modified local electronic structures at the Fe impurities and theenhanced spin-dependent reflections at the $\alpha-Fe_{2}O_{3} phase in the magnetic layer.

Electrical properties of Ultra-Shallow Junction formed by using Epitaxial $CoSi_{2}$ Thin Film as Diffusion Source ($CoSi_{2}$ 에피박막을 확산원으로 이용하여 형성한 매우 얇은 접합의 전기적 특성)

  • Koo, Bon-Cheol;Shim, Hyun-Sang;Jung, Yun-Sil;Bae, Kyoo-Sik
    • Korean Journal of Materials Research
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    • v.8 no.5
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    • pp.470-473
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    • 1998
  • $As^+$ was ion-implanted onto $CoSi_{2}$ thin films formed by rapidly thermal-annealed Co/Ti bilayers. Then the specimens were drive-in annealed at 500~100$0^{\circ}C$ to form ultra-shallow $n^+$p junction diodes and to measure their 1- V characteristics. When drive-in annealed at 50$0^{\circ}C$ for 280 sec., 50 nm thick ultra-shallow junctions were formed and di¬odes showed the best 1- V characteristics with low leakage current. In particular. the leakage current was 2 orders lower than that of diodes formed by using Co monolayer. It was attributed to uniform $CoSi_{2}$/Si interfaces.

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Characterization of AlN Thin Films Grown by Plasma Assisted Molecular Beam Epitaxy on Si Substrate (실리콘 기판위에 플라즈마 분자선 에피택시를 이용하여 성장된 질화알루미늄 박막의 특성분석)

  • 홍성의;한기평;백문철;조경익;윤순길
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.13 no.10
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    • pp.828-833
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    • 2000
  • Growth characteristics and microstructure of AIN thin films grown by plasma assisted molecular beam epitaxy on Si substrates have been investigated. Growing temperature and substrate orientation were chosen as major variables of the experiment. Reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the micorstructure of the films. On Si(100) substrates, AlN thin films were grown along the hexagonal c-axis preferred orientation at temperature range 850-90$0^{\circ}C$. However on Si(111), the AlN films were epitaxially grown with directional coherency in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112) at 85$0^{\circ}C$ and the epitaxial coherencry seemed to be slightly distorted with increasing temperature. The microstructure of AlN thin films on Si(111) substrates showed that the films include a lot of crystal defects and there exist micro-gaps among the columns.

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Characterization of AlN thin films grown by plasma assisted molecular beam epitaxy on Si substrates (실리콘 기판 위에 플라즈마 분자선 에피택시를 이용하여 성장된 질화알루미늄 박막의 특성분석)

  • 홍성의;한기평;백문철;조경익
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2000.07a
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    • pp.111-114
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    • 2000
  • Growth characteristics and microstructure of AlN thin films grown by plasma assisted molecular beam epitaxy on Si substrates have been investigated. Growing temperature and substrate orientation were chosen as major variables of the experiment. Reflection high energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscopy (AFM) and transmission electron microscopy/diffraction (TEM/TED) techniques were employed to characterize the microstructure of the films. On Si(100) substrates, AlN thin films were grown along the hexagonal c-axis preferred orientation at temperature range 850-90$0^{\circ}C$. However on Si(111), the AlN films were epitaxially grown with directional coherency in AlN(0001)/Si(111), AlN(1100)/Si(110), and AlN(1120)/Si(112) at 85$0^{\circ}C$ and the epitaxial coherencry seemed to be slightly distorted with increasing temperature. The microstructure of AlN thin films on Si(111) substrates showed that the films include a lot of crystal defects and there exist micro-gaps among the columns.

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P-TYPE Zn Diffused by Ampoule-tube Method into $GaAs_{0.40}P_{0.60}$ and the Properties of Electroluminescence (기상 확산법에 의한 P-Type Zn 확산과 GaAs0.6P0.4의 전계발광 특성)

  • Kim, Da-Doo;So, Soo-Jin;Song, Min-Jong;Park, Choon-Bae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.11a
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    • pp.510-513
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    • 2003
  • Our Zn diffusion into n-type $GaAs_{0.40}P_{0.60}$ used ampoule-tube method to increase IV. N-type epitaxial wafers were preferred by $H_2SO_4$-based pre-treatment. $SiO_2$ thin film was deposited by PECVD for some wafers. Diffusion times and diffusion temperatures respectability are 1, 2, 3 hr and 775, $805^{\circ}C$. LED chips were fabricated by the diffused wafers at Fab. The peak wavelength of all chips showed about $625{\sim}650\;nm$ and red color. The highest IV is about 270 mcd at the diffusion condition of $775^{\circ}C$, 3h for the wafers which didn't deposit $SiO_2$ thin films. Also, the longer diffusion time is the higher IV for the wafers which deposit $SiO_2$ thin films.

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Growth and characterization of ZnO thin films on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy (R-면 사파이어 기판 위에 플라즈마 분자선 에피탁시법을 이용한 산화아연 박막의 성장 및 특성평가)

  • Han, Seok-Kyu;Hong, Soon-Ku;Lee, Jae-Wook;Lee, Jeong-Yong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2006.06a
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    • pp.155-156
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    • 2006
  • Single crystalline ZnO fims were successfully grown on r-plane sapphire substrate by plasma-assisted molecular beam epitaxy. Epitaxial relationship between the ZnO film and the-r-plane sapphire was determined to be [-1101]$Al_2O_3\;{\parallel}$ [0001]ZnO, [11-20]$Al_2O_3\;{\parallel}$ [-1100]ZnO based on the in-situ RHEED analysis and confirmed again by HRXRD measurements. Grown (11-20) ZnO films showed faceted structure along the <0001> direction and the RMS roughness was about 4 nm.

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Fabrication and Electrical Transport Characteristics of All-Perovskite Oxide DyMnO3/Nb-1.0 wt% Doped SrTiO3 Heterostructures

  • Wang, Wei Tian
    • Korean Journal of Materials Research
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    • v.30 no.7
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    • pp.333-337
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    • 2020
  • Orthorhombic DyMnO3 films are fabricated epitaxially on Nb-1.0 wt%-doped SrTiO3 single crystal substrates using pulsed laser deposition technique. The structure of the deposited DyMnO3 films is studied by X-ray diffraction, and the epitaxial relationship between the film and the substrate is determined. The electrical transport properties reveal the diodelike rectifying behaviors in the all-perovskite oxide junctions over a wide temperature range (100 ~ 340 K). The forward current is exponentially related to the forward bias voltage, and the extracted ideality factors show distinct transport mechanisms in high and low positive regions. The leakage current increases with increasing reverse bias voltage, and the breakdown voltage decreases with decrease temperature, a consequence of tunneling effects because the leakage current at low temperature is larger than that at high temperature. The determined built-in potentials are 0.37 V in the low bias region, and 0.11 V in the high bias region, respectively. The results show the importance of temperature and applied bias in determining the electrical transport characteristics of all-perovskite oxide heterostructures.

Formation of $CoSi_2$ Film and Double Heteroepitaxial Growth of $Si/epi-CoSi_2/Si$(111) by Solid Phase Epitaxy (고상 에피택시에 의한 초박막 $CoSi_2$ 형성과 $Si/epi-CoSi_2/Si$(111)의 이중헤테로 에피택셜 성장)

  • Choi, Chi-Kyu;Kang, Min-Sung;Moon, Jong;Hyun, Dong-Geul;Kim, Kun-Ho;Lee, Jeong-Yong
    • Korean Journal of Materials Research
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    • v.8 no.2
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    • pp.165-172
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    • 1998
  • Epitaxial ultrathin films of $CoSi_2$ and double heteroepitaxial structure of Si/$CoSi_2$/Si(lll) were prepared on Si(111)-$7\times{7}$ substrate by in situ solid-phase epitaxy in a ultrahigh vacuum(LHV). The phase, chemical composition, crystallinity, and the microsructure of the Si/$CoSi_2$/Si(lll) interface were investigated by 2-MeV $^4He^{++}$ ion backscattering spectrometry, X-ray diffraction, and high-resolution transmission electron microscopy. The growth mode of the Co film was the Stransky-Krastanov type with texture when the substrate temperature was room temperature. A-type $CoSi_2$ ultrathin film was grown by deposition of about 50A Co on Si(ll1)-$7\times{7}$ substrate followed by in situ annealing at $700^{\circ}C$ for 10 min. The matching face relationships were $CoSi_2$[110]//Si[110] and $CoSi_2$(002)//Si(002) with no misorientation angle. The A-type $CoSi_2$/Si(lll) interface was abrupt and coherent. The best epi-Si/epi-$CoSi_2$2(A-type)/Si(lll) structure was obtained by deposition of Si film on the CoSii at $500^{\circ}C$ followed by in situ annealing at $700^{\circ}C$ for 10 min in UHV.

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Characterization of epitaxial layers on beta-gallium oxide single crystals grown by EFG method as a function of different crystal faces and off-angle (EFG 법으로 성장시킨 β-Ga2O3 단결정의 다양한 결정면, off-angle에 따른 epitaxial layer의 특성 분석)

  • Min-Ji Chae;Sun-Yeong Seo;Hui-Yeon Jang;So-Min Shin;Dae-Uk Kim;Yun-Jin Kim;Mi-Seon Park;Gwang-Hee Jung;Jin-Ki Kang;Hae-Yong Lee;Won-Jae Lee
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.34 no.4
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    • pp.109-116
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    • 2024
  • β-Ga2O3 is a representative ultra-wide bandgap (UWBG) semiconductor that has attracted much attention for power device applications due to its wide-bandgap of 4.9 eV and high-breakdown voltage of 8 MV/cm. In addition, because solution growth is possible, it has advantages such as fast growth rate and lower production cost compared to SiC and GaN [1-2]. In this study, we have successfully grown Si-doped 10 mm thick Si-doped β-Ga2O3 single crystals by the EFG (Edge-defined Film-fed Growth) method. The growth direction and growth principal plane were set to [010] / (010), respectively, and the growth speed was 7~20 mm/h. The as-grown β-Ga2O3 single crystal was cut into various crystal planes (001, 100, ${\bar{2}}01$) and off-angles (1o, 3o, 4o), and then surface processed. After processed, the homoepitaxial layer was grown on the epi-ready substrate using the HVPE (Halide vapor phase epitaxy) method. The processed samples and the epi-layer grown samples were analyzed by XRD, AFM, OM, and Etching to compare the surface properties according to the crystal plane and off-angle.

Synthesis of La0.7Sr0.3Mn1-xIrxO3 thin-films in search of superconductivity

  • Byeongjun Seok;Youngdo Kim;Donghan Kim;Jongho Park;Changyoung Kim
    • Progress in Superconductivity and Cryogenics
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    • v.25 no.2
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    • pp.10-13
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    • 2023
  • High-TC superconductivity (HTSC) has been the central issue in the field of condensed matter physics for decades. An essential part of the research on superconductivity is finding new exotic superconductors. It was recently suggested that Ir-substituted La0.7Sr0.3MnO3 (LSMIO) is a new high-TC superconductor. However, systematic studies to experimentally verify the superconductivity have not been done. Here, we report the growth processes of LSMIO thin films and their electrical transport properties. We observed a clear negative correlation between the intensity of the laser utilized for film deposition and the Curie temperature of the deposited film. We attributed this effect to the suppression of Sr concentration in the LSMIO films as the laser intensity increased. However, our LSMIO films show conventional ferromagnetism instead of HTSC. To realize the HTSC in LSMIO systems, further exploration of diverse compositions of LSMIO compounds is essential.