• 한국진공학회지
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• 제7권4호
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• pp.355-360
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• 1998

250$\AA$과 1340$\AA$두께의 에피탁시($Ba_{0.5}Sr_{0.5}$)$TiO_3$(혹은 BST)박막을 MgO(001)단결정기 판에 펄스형 레이저 증착법(pulsed laser deposition)으로 제조한 후 방사광 X선 산란을 이 용하여 분석하였다. 박막은 초기에 MgO(001)단결정 기판과cube-on-cube관계로 증착되며, 박막이 성장함에 따라 이 관계를 계속 유지하면서 성장하는 것으로 판단된다. 한편 박막이 성장함에 따라 박막의 표면은 급격하게 거칠어지는 반면 기판과 박막 사이의 계면의 거칠기 는 크게 변하지 않았다. 에피탁시 BST박막의 초기상태에서는 c축이 기판과 수직한 방향으 로 배향된 정방정구조를 지녔으며, 아울러 기판의 수직(out-of-plane) 및 평형(in-plane)방향 으로의 모자익(mosaic)분포가 좁아짐을 확인하였다.

• 한국염색가공학회지
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• 제8권6호
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• pp.27-32
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• 1996

This research is to investigate the reaction kinetics by air-lift bioreactor using calcium hydroxide, the neutralization agent and immobilization media, for removing ethylene glycol remained after chemical pretreatment. It was found that the optimum hydraulic retention time was obtained as 24.2hours at the optimum F/M ratio of 1.32kg-$TCOD_{Mn}$/day.kg-MLVSS, and then, infiuent $TCOD_{Mn}$ and MLVSS concentration were 3,290mg/l and 2,472mg/l, respectively. During the steady state, the kinetics constants such as maximum specific substrate removal rate, half saturation velocity coefficient, yield coefficient and endogenous respiration coefficient were estimated in the base of $TCOD_{Mn}$ as substrate concentration. And they were 1.47day$^{-1}$, 3.95mg/l, 0.391 and 0.092day$^{-1}$, respectively. And also, the oxgen use coefficients for cell synthesis, a', and energy of maintenance, b', were obtained as 0.4kg-O$_{2}$/kg-$TCOD_{Mn}$ and 0.056day$^{-1}$, at the steady state by the experimental result of oxygen uptake rate.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2000년도 제18회 학술발표회 논문개요집
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• pp.122-122
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• 2000

Magnesium oxide is thermodynamically very stable, has a low dielectric constant and a low refractive index, and has been widely used as substrate for growing various thin film materials, particulary oxides of the perovskite structure. There has been a considerable interest in integrating the physical properties of these oxides with semiconductor materials such as GaAs and Si. In this regard, it is considered very important to be able to grow MgO buffer layers epitaxially on the semiconductors. Various oxide films can then be grown on such buffer layers eliminating the need for using MgO single crystal substrates. Vapor phase epitaxy of magnesium oxide has been accomplished on Si(001) substrates in a high vacuum chamber using the single precursor methylmagnesium tert-butoxide in the temperature range 750-80$0^{\circ}C$. For the epitaxy of the MgO films, SiC buffer layers had to be grown on Si(001). The films were characterized by reflection high energy electron diffraction (RHEED) in situ in the growth chamber, and x-ray diffraction (XRD), x-ray pole figure analysis, scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS) after the growth.

• 열처리공학회지
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• 제33권3호
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• pp.124-128
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• 2020

Recently, many studies on growth of single crystal diamond using MPECVD have been conducted. The heteroepitaxial method is one of the methods for growing diamonds on a large-area substrate, and research on synthesis of single crystal diamonds using SrTiO₃, MgO, and sapphire substrates has been attempted. In addition, research is being conducted to reduce the internal stress generated during diamond growth and to improve the crystallinity of the diamond. The compressive stress generated therein causes peeling and bowing from the substrate. This study aimed to synthesize heteroepitaxial single crystal diamonds with high crystallinity by surface modification. A diamond thin film was first grown on a sapphire/Ir substrate by MPECVD, and then etched with H₂ gas to modified the morphology and roughness of the surface. A secondary diamond layer was grown on the surface, and the internal stress, crystallinity of the diamond were investigated. As a result, the fabrication of single crystal diamonds with improved crystallinity was confirmed.

• 한국전기전자재료학회논문지
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• 제18권5호
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• pp.464-467
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• 2005

BiSrCaCuO superconducting ceramic thick films were fabricated by chemical process. The x ray diffraction pattern of the BiSrCaCuO thick films contained 110 K phase. The critical temperature of BiSrCaCuO thick films were Tc=95 K-97 K. The critical temperature and critical density of BiSrCaCuO thick film grown at $750 {\circ}C$ were Tc = 95 K and $Jc= 7{\times}10^{6} A/cm^{2}$ We obtained high-Jc as-grown BiSrCaCuO on an MgO substrate by low fressure CVD.

• 한국재료학회지
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• 제27권9호
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• pp.495-500
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• 2017

Oxide layers were formed by an environmentally friendly plasma electrolytic oxidation (PEO) process on AZ91 Mg alloy. PEO treatment also resulted in strong adhesion between the oxide layer and the substrate. The influence of the KF electrolytic solution and the structure, composition, microstructure, and micro-hardness properties of the oxide layer were investigated. It was found that the addition of KF instead of KOH to the $Na_2SiO_3$ electrolytic solution increased the electrical conductivity. The oxide layers were mainly composed of MgO and $Mg_2SiO_4$ phases. The oxide layers exhibited solidification particles and pancake-shaped oxide melting. The pore size and surface roughness of the oxide layer decreased considerably with an increase in the concentration of KF, while densification of the oxide layers increased. It is shown that the addition of KF to the basis electrolyte resulted in fabricating of an oxide layer with higher surface hardness and smoother surface roughness on Mg alloys by the PEO process. The uniform thickness of the oxide layer formed on the Mg alloy substrates was largely determined by the electrolytic solution with KF, which suggests that the composition of the electrolytic solution is one of the key factors controlling the uniform thickness of the oxide layer.

• 한국진공학회지
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• 제5권1호
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• pp.62-66
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• 1996

$(Ba_{1-x}Sr_xTiO_3$ (BST) thin films have been grown on Pt-coated MgO by metal -organic chemical vapor deposition. X-ray diffraction results showed that BST films were grown on a Pt/MgO substrate with (100) preferred orientation perpendicular to the surface. The lineawr relationship of P-E curve obtained form hysteresis loop measurement indicated that the BST films had a Curie transitions below room temperature . Films deposited at $900^{\circ}C$ exhibited a smooth and dense microstructure, a dielectric constant of 202, and a dissipation facotr of 0.02 at 100kHz. The leakage current density of the BST films is about $2\times10^{-10} \;A/\textrm{cm}^2$$ at an applied electric field of 0.2 MV/cm. The electrical behavior on the current-voltage characteristics is well explained by the bulk-limited Pool-Frenkel emission.

• 한국표면공학회지
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• 제29권5호
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• pp.415-423
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• 1996

Thin film technologies for fabricating SQUIDs involve etching and deposition procedures with the proper substrate materials and $YBa_2Cu_3O_{7-d}$ (YBCO) as the high $T_c$ superconductor. YBCO were prepared on various substrates of MgO, $SrTiO_3$, and $LaAlO_3$ by using off-axis magnetron sputtering methods and annealing in-situ. The parameters of film fabrication processes had been optimized to yield good quality films in terms of the critical temperature $T_c$ and the critical current density $J_c$. The optimized processes yielded $T_C$>90K along with $J_c$>$10_6A$$extrm{cm}^2$ at 77K and>$2\times10_7A/Cm^2$ at 5K. We fabricated step-edge type dc-SQUIDs and directly coupled magnetometers, producing step edges on MgO(100) substrates by etching with Ar-ion beam, depositing YBCO material on them, then patterning them by using ion-milling technique. Circuitizing washer-shape SQUIDs to possess a pair of step-edge junctions of 2-5$\mu$ line width with a high angle>$50^{\circ}C$ , we examined their I-V characteristics thoroughly and Shapiro steps clearly as we irradiate microwaves of 8-20 GHz frequency.

• Progress in Superconductivity
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• 제6권1호
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• pp.69-73
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• 2004

Ni alloy tape is electropolished to be used as a metal substrate for fabrication of IBAD (ion-Beam Assisted Deposition)-MgO texture template fur HTS coated conductor. Electropolishing is needed to obtain a very smooth surface of Ni alloy tape because the in-plane texture of templates is sensitive to the roughness of metal substrate. The critical current of YBCO coated conductor depends on the texture of YBCO that depends on the texture of the IBAD MgO layer. And so the smoothness of the metal substrate is directly related to the superconducting properties of the coated conductor. In this study, we have prepared a reel-to-reel electropolishing apparatus to polish the Ni alloy tapes for IBAD. Various electropolishing conditions were investigated to improve the surface roughness. Hastelloy tape is continuously electropolished with high polishing current density (0.5 ∼ 2 A/$\textrm{cm}^2$) and fast processing time (1 ∼ 3 min). Polished hastelloy tapes have surface roughness(RMS) of below 1 nm on a 5 ${\times}$ 5 $\mu\m^2$ from AFM and SEM.

• Journal of Korean Vacuum Science & Technology
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• 제5권1호
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• pp.1-6
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• 2001

We measured the simultaneous, time-resolved spectra of photon emission, electron emission, and frictional force during the abrasion single crystal MgO with a diamond stylus in vacuum. phE and EE signal can be detected with millisecond resolution during the wear of a single crystal MgO substrate with a diamond stylus. The emissions and wear behavior are strong function of surface condition, load and stylus velocity. Measurement on annealed vs as-received material show that the luminescence is primarily due to deformation, and the electron emission is primarily due to fracture. These emissions provide insight into the processes responsible for catastrophic failure of ceramics in wear applications.