• Bulletin of the Korean Chemical Society
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• v.5 no.1
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• pp.41-44
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• 1984

The oxidation of carbon monoxide has been investigated on Ni-doped ${\alpha}-Fe_2O_3$ catalyst at 300 to $450^{\circ}$. The oxidation rates have been correlated with 1.5-order kinetics; first with respect to CO and 1/2 with respect to $O_2$. Carbon monoxide is adsorbed on lattice oxygen of Ni-doped ${\alpha}-Fe_2O_3$, while oxygen appears to be adsorbed on oxygen vacancy formed by Ni-doping. The conductivities show that adsorption of CO on O-lattice produces conduction electron and adsorption of $O_2$ on O-vacancy withdraws the conduction electron from vacancy. The adsorption process of CO on O-lattice is rate-determining step and dominant defect of Ni-doped ${\alpha}-Fe_2O_3$ is suggested from the agreement between kinetic and conductivity data.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.3
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• pp.89-95
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• 2001

The CZ-silicon crystal was annealed at $1350^{\circ}C$ to dissolve the vacancy type grown-in defects. A this temperature, the equilibrium concentration of the oxygen in the silicon crystal is around $1.7{\times}10^{18}$ which induces the oxygen undersaturation in the silicon crystal. This situation results in the faster dissolution of the grown-in defects in the bulk of the silicon wafer than near the surface. This indicates the possibility that the presence of the higher concentration of silicon interstitial hinders the dissolution of the grown-in defects, which were known to compose of the vacancy clusters with surrounding silicon oxide film. This expectation was confirmed by the observation that the slower dissolution of the grown-in defects near the surface of the silicon wafer in the oxygen atmosphere than in the argon atmosphere. This result is quite opposite to the previous argument hat presence of the excess silicon interstitial leads to faster dissolution of the vacancy type defects.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.61-64
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• 2008

$Pr_{0.3}Sr_{0.7}Co_{0.3}Fe_{0.7}O_{3-\delta}$ (PSCF3737) was prepared and characterized as a cathode material for intermediate temperature-operating solid oxide fuel cell (IT-SOFC). X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), extended X-ray absorption fine structure (EXAFS), and electrical property measurement were carried out to study cathode performance of the material. XPS and EXAFS results proved that oxygen vacancy concentration was decreased and lattice constants of the perovskite structure material were increased by doping Fe up to 70 mol% at B-site of the crystal structure, which also extended the distance between oxygen and neighbor atoms. Thermal expansion coefficient (TEC) of PSCF3737 is smaller than that of $Pr_{0.3}Sr_{0.7}CoO_{3-\delta}$(PSC37) due to lower oxygen vacancy concentration. PSCF3737 showed better cathode performance than PSC37. It might be due good adhesion by a smaller difference of TEC between $Gd_{0.1}Ce_{0.9}O_2$ (CGO91) and electrode. Composite material PSCF3737-CGO91 showed better compatibility of TEC than PSCF3737. However, PSCF3737-CGO91 did not represent higher electrochemical property than PSCF3737 due to decreased reaction sites by CGO91.

• Korean Journal of Materials Research
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• v.17 no.9
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• pp.458-462
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• 2007

The effect of oxygen in the synthesis of oxide nanowires by using carbothermal reduction process have been studied thermodynamically and kinetically. By using laboratory air, ZnO nanowires could be fabricated in the carbothermal reduction process and a metal oxidation process. As the processing pressure decreases, the diameter of the nanowires decreases and the oxygen vacancy increases. As the processing pressure increases, the oxygen vacancy decreases and the shape of the ZnO becomes plate-like.

• Nuclear Engineering and Technology
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• v.51 no.5
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• pp.1398-1405
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• 2019

We use a molecular dynamics simulation to explore thermal transport in oxide nuclear fuels with point defects. The effect of vacancy and substitutional defects on the thermal conductivity of plutonium dioxide and uranium dioxide is investigated. It is found that the thermal conductivities of these fuels are reduced significantly by the presence of small amount of vacancy defects; 0.1% oxygen vacancy reduces the thermal conductivity of plutonium dioxide by more than 10%. The missing of larger atoms has a more detrimental impact on the thermal conductivity of actinide oxides. In uranium dioxide, for example, 0.1% uranium vacancies decrease the thermal conductivity by 24.6% while the same concentration of oxygen vacancies decreases the thermal conductivity by 19.4%. However, uranium substitution has a minimal effect on the thermal conductivity; 1.0% uranium substitution decreases the thermal conductivity of plutonium dioxide only by 1.5%.

• Journal of the Korean Ceramic Society
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• v.34 no.12
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• pp.1221-1226
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• 1997

The effects of sintering atmosphere and dopant addition on the behavior of densification and grain growth of SnO2 ceramics were investigated with consideration of defect chemistry. CoO and Nb2O5 were chosen as dopants, and oxygen and nitrogen were used for controlling of sintering atmospheres. With the decrease of oxygen partial pressure, densification was depressed due to evaporation of SnO2 ceramics. In the case of SnO2 sintering, the addition of CoO, which produced oxygen vacancy in SnO2 ceramics, led to acceleration of densification and grain growth. On the contrary, when Nb2O5 as a dopant producing Sn vacancy was added to SnO2 ceramics, densification and grain growth were simultaneously retarded. As results, it was conformed that diffusion of oxygen ions was rate determinant in densification and grain growth of SnO2 ceramics.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.216.1-216.1
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• 2015

본 연구에서는 용액 공정 기반 AZTO (Aluminum-Zinc-Tin Oxide, AlZnSnO) 박막 트랜지스터를 제작하여 Al (Aluminum) 도핑과 열처리 온도의 가변을 통한 특성 향상을 확인하였다. ZTO 용액의 Zn:Sn 비율(4:7)을 고정하고 Al 도핑(0~8.3%)과 열처리 온도($350{\sim}550^{\circ}C$)를 가변하였다. 실험 결과 Al 도핑이 증가할수록 드레인 전류는 감소하고 문턱 전압이 양의 방향으로 이동하면서 포화 이동도와 아문턱 기울기가 감소하였다. 열처리 온도가 증가할 때는 드레인 전류가 증가하고 문턱 전압은 음의 방향으로 이동하며 이동도와 아문턱 기울기가 증가하였다. Al 도핑은 강한 금속-산소 결합에 의해 oxygen vacancy와 전자 농도가 감소하게 하여 드레인 전류, 이동도, 아문턱 기울기의 감소와 양의 방향 문턱 전압 이동을 야기한다. 열처리 온도가 높아지면 반도체 층의 분자 구조가 더 밀집되고 oxygen vacancy 가 증가하며, 이는 전자 농도의 증가로 이어져 Al 도핑의 효과와 반대의 경향을 보인다. 실험 결과를 통해 Al:Zn:Sn=0.5:4:7의 비율과 $350^{\circ}C$ 열처리 조건에서 문턱 전압과 이동도, 아문턱 기울기, 전류 온오프 비($I_{on}/I_{off}$)가 각각 3.54V, $0.16cm^2/Vs$, 0.43 V/dec, $8.1{\times}10^5$으로 우수한 특성을 확인하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.1
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• pp.11-16
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• 2016

The conduction behavior and electron concentration change in a-IGZO thin-films according to the RTA (rapid thermal annealing) were studied. The electrical characteristics of TFTs (thin-film-transistors) annealed by different temperatures were measured. The sheet resistance, electron concentration, and oxygen vacancy of a-IGZO film were measured by the four-point-probe-measurement, hall-effect-measurement, and XPS analysis. The RTA process increased the driving current of IGZO TFTs but the VTH shifted to the negative direction at the same time. When the RTA temperature is higher than $250^{\circ}C$, the leakage current at off-state increased significantly. This is attributed to the increase of oxygen vacancy resulting in the increase of electron concentration. We demonstrate that the RTA is a promising process to adjust the VTH of TFT because the RTA process can easily modify the electron concentration and control the conductivity of IGZO film with short process time.

• Journal of the Korean Magnetics Society
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• v.16 no.4
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• pp.206-210
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• 2006

A room-temperature ferromagnetism has been observed for oxygen-deficient rutile and anatase $TiO_{2-{\delta}}$ films. XPS data revealed the existence of $Ti^{3+}$ ions, for compensating the charge imbalance caused by oxygen vacancies in the film. The observed ferromagnetism is attributable to the spin ($3d^1$) alignment of the $Ti^{3+}$ ions. Such spin alignment can happen through magnetic polaron formed by trapped electron in oxygen vacancy and magnetic $Ti^{3+}$ ions around it.

• Transactions on Electrical and Electronic Materials
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• v.15 no.6
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• pp.315-319
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• 2014

In this paper, we investigate visible light stress instability in radio frequency (RF) sputtered a-IGZO thin film transistors (TFTs). The oxygen flow rate differs during deposition to control the concentration of oxygen vacancies, which is confirmed via RT PL. A negative shift is observed in the threshold voltage ($V_{TH}$) under illumination with/without the gate bias, and the amount of shift in $V_{TH}$ is proportional to the concentration of oxygen vacancies. This can be explained to be consistent with the ionization oxygen vacancy model where the instability in $V_{TH}$ under illumination is caused by the increase in the channel conductivity by electrons that are photo-generated from oxygen vacancies, and it is maintained after the illumination is removed due to the negative-U center properties.