• 한국초전도ㆍ저온공학회논문지
• /
• 제22권2호
• /
• pp.21-25
• /
• 2020

We investigated the flux pinning property of GdBa₂Cu₃O_7-x (GdBCO) films on top of La_0.7Sr_0.3MnO₃ (LSMO) nanoparticles deposited by a surface decoration. Both GdBCO films and LSMO nano particles were deposited by pulsed laser deposition and the number of laser pulses were varied from 80 to 320 in order to control the density of the LSMO nanoparticles. The magnetization data at 77 K showed that the critical current density (J_c) was enhanced in all of the GdBCO films with LSMO nanoparticles and that the J_c enhancement was found to be inversely proportional to the LSMO nanoparticle density. Structural analyses revealed that LSMO nanoparticles induce a compressive strain in the GdBCO films resulting in a disordering in the CuO₂ plane. Therefore, the enhanced flux pinning property in the GdBCO with LSMO nanoparticles was attributed to the competing effect between the increase of pinning centers and the increase of compressive strain in the superconducting phase.

• 한국재료학회지
• /
• 제14권6호
• /
• pp.413-419
• /
• 2004

Recently, Silicon On Insulator (SOI) devices emerged to achieve better device characteristics such as higher operation speed, lower power consumption and latch-up immunity. Nevertheless, there are many detrimental defects in SOI wafers such as hydrofluoric-acid (HF)-defects, pinhole, islands, threading dislocations (TD), pyramid stacking faults (PSF), and surface roughness originating from quality of buried oxide film layer. Although the number of defects in SOI wafers has been greatly reduced over the past decade, the turn over of high-speed microprocessors using SOI wafers has been delayed because of unknown defects in SOI wafers. A new characterization method is proposed to investigate the crystalline quality, the buried oxide integrity and some electrical parameters of bonded SOI wafers. In this study, major surface defects in bonded SOI are reviewed using HF dipping, Secco etching, Cu-decoration followed by focused ion beam (FIB) and transmission electron microscope (TEM).

• Carbon letters
• /
• 제13권1호
• /
• pp.56-59
• /
• 2012

The defect sites on chemical vapor deposition grown graphene are investigated through the selective electrochemical deposition (SED) of Au nanoparticles. For SED of Au nanoparticles, an engineered potential pulse is applied to the working electrode versus the reference electrode, thereby highlighting the defect sites, which are more reactive relative to the pristine surface. Most defect sites decorated by Au nanoparticles are situated along the Cu grain boundaries, implying that the origin of the defects lies in the synthesis of uneven graphene layers on the rough Cu surface.

• Journal of Electrochemical Science and Technology
• /
• 제9권4호
• /
• pp.282-291
• /
• 2018

The pristine fluorine-doped $SnO_2$ (abbreviated as FTO) inverse opal (IO) was developed using a 410 nm polystyrene bead template. The nanolayered copper tungsten oxide ($CuWO_4$) was decorated on the FTO IO film using a facile electrochemical deposition, subsequently followed by annealing at $500^{\circ}C$ for 90 min. The morphologies, crystalline structure, optical properties and photoelectrochemical characteristics of the FTO and $CuWO_4$-decorated FTO (briefly denoted as $FTO/CuWO_4$) IO film were investigated by field emission scanning electron microscopy, X-ray diffraction, UV-vis spectroscopy and electrochemical impedance spectroscopy, showing FTO IO in the hexagonally closed-pack arrangement with a pore diameter and wall thickness of about 300 nm and 20 nm, respectively. Above this film, the $CuWO_4$ was electrodeposited by controlling the cycling number in cyclic voltammetry, suggesting that the $CuWO_4$ formed during 4 cycles (abbreviated as $CuWO_4$(4 cycles)) on FTO IO film exhibited partial distribution of $CuWO_4$ nanoparticles. Additional distribution of $CuWO_4$ nanoparticles was observed in the case of $FTO/CuWO_4$(8 cycles) IO film. The $CuWO_4$ layer exhibits triclinic structure with an indirect band gap of approximately 2.5 eV and shows the enhanced visible light absorption. The photoelectrochemical (PEC) behavior was evaluated in the 0.5 M $Na_2SO_4$ solution under solar illumination, suggesting that the $FTO/CuWO_4$(4 cycles) IO films exhibit a photocurrent density ($J_{sc}$) of $0.42mA/cm^2$ at 1.23 V vs. reversible hydrogen electrode (RHE, denoted as $V_{RHE}$), while the FTO IO and $FTO/CuWO_4$(8 cycles) IO films exhibited a $J_{sc}$ of 0.14 and $0.24mA/cm^2$ at $1.23V_{RHE}$, respectively. This difference can be explained by the increased visible light absorption by the $CuWO_4$ layer and the favorable charge separation/transfer event in the cascading band alignment between FTO and $CuWO_4$ layer, enhancing the overall PEC performance.

• Transactions on Electrical and Electronic Materials
• /
• 제5권4호
• /
• pp.143-147
• /
• 2004

Surface defects and bulk defects on SOI wafers are studied. Two new metrologies have been proposed to characterize surface and bulk defects in epitaxial layer transfer (ELTRAN) wafers. They included the following: i) laser scattering particle counter and coordinated atomic force microscopy (AFM) and Cu-decoration for defect isolation and ii) cross-sectional transmission electron microscope (TEM) foil preparation using focused ion beam (FIB) and TEM investigation for defect morphology observation. The size of defect is 7.29 urn by AFM analysis, the density of defect is 0.36 /cm$^2$ at as-direct surface oxide defect (DSOD), 2.52 /cm$^2$ at ox-DSOD. A hole was formed locally without either the silicon or the buried oxide layer (Square Defect) in surface defect. Most of surface defects in ELTRAN wafers originate from particle on the porous silicon.

• Applied Biological Chemistry
• /
• 제45권3호
• /
• pp.179-184
• /
• 2002

한국산 검정콩 종피의 천연색소로의 이용가능성을 알아보기 위하여 온도, 당류, 유기산류, 비타민 C 그리고 금속 이온의 영향을 살펴보았다. 검정콩 색소의 열안정성은 다른 안토시아닌 계열의 색소와 비교할 때 유사하거나 더 안정한 것으로 나타났다. 당류의 영향에서는 타 색소와는 달리 농색화 현상은 일어나지 않았고 저장성에서는 모두 포도당에서 양호하였다. 유기산에서는 모든 첨가구에서 색의 강도가 증가하였으며 비타민 C 첨가의 경우 안토시아닌 색소에 부정적인 영향을 나타내었고 금속이온의 영향에서는 $Cu^{2+}$와 $Zn^{2+}$ 이온에서 안정하였으며 $Mn^{2+}$에서는 불안정하였다. 이상의 결과를 종합해 볼 때 검정콩 종피색소는 pH 3에서 다른 색소와 비교하여 상당히 안정한 색소임을 알 수 있었다.

• 박물관보존과학
• /
• 제24권
• /
• pp.1-16
• /
• 2020

대구 달성 고분군 중 하나인 55호분에서 발견된 부장품 중 삼엽문이자태도의 재보존처리와 제작 기법에 관한 연구이다. 이자태도는 모도가 2점, 자도가 4점이 부착된 이합도이고 출토된 완형으로는 유일하다. 과거 2회의 보존처리가 실시된 기록이 있으며 이번에 균열부 보강제 교체를 위한 재보존처리와 함께 컴퓨터 단층촬영(CT), XRF분석, 실체현미경 관찰을 통해 유물의 재질, 성분, 제작 기법을 조사하였다. 주성분은 구리(Cu)이고 금색 부분에서는 금(Au)과 수은(Hg)이 함께 검출된 것으로 보아 구리에 수은 아말감 금도금을 한 금동으로 추정된다. 제작 기법을 조사한 결과 둥근 삼엽문의 환두부와 병부의 연결은 슴베 부분을 만들어 끼웠고 병판만 금속판으로 제작되어 있는 것을 보아 장식으로서의 기능이 높다고 판단할 수 있다. 상부 자도의 결합 방식은 모도와 같고, 하부 자도는 하나의 금속판을 재단하여 만들었다. 검초는 총 2개의 판을 재단하여 만들었고 상부 자도를 검초에 고정하기 위해 자도 도신부의 아래쪽에 지지대를 넣었으며 하부 자도는 검초 일부를 재단하여 안으로 꽂아 넣었다. 표현된 문양은, 환두부는 삼엽문, 병판은 횡주 연호문, 초구금구와 초미금구는 파상형 점열문, 어미형 초미금구는 점열문을 시문하여 제작되었다.

• Applied Biological Chemistry
• /
• 제46권3호
• /
• pp.251-256
• /
• 2003

한국산 인삼을 60% acetone으로 추출하여 Sepadex LH-20 gel column chromatography, MCI-CHP 20 gel column chromatography, ${\mu}-Bondapack\;C_{18}$ gel column chromatography을 이용하여 polyphenol 분획물을 3종류를 분리하여 항산화 효과, phospholipase $A_2$ 저해효과 및 암세포 증식억제 효과를 검토하였다. 항산화 효과에서 분획물 I은 150 ppm에서 $Cu^{2+},\;KO_2$ 그리고 $H_2O_2$에 대하여 각각 48.16%, 79.71%, 43.55%를 나타내었고 DPPH 수소공여능은 분획물 II가 200 ppm에서 35.17%의 라디칼소거능을 보였다. 분획물 III는 $Fe^{2+}$, OH가 존재 시 150 ppm에서 48.49%, 25%의 항산화효과를 나타내었다. Phospholipase $A_2$ 저해활성은 분획물 III이 $60\;{\mu}/ml$에서 48.9%의 활성을 나타냈다. HT 29 cell에 대한 인삼의 세포 독성은 분획물 II에서 0.25 mg/ml에서 73.29%의 가장 높은 억제능을 나타내었다.