• Title/Summary/Keyword: Lattice defect

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Kinetics and Mechanisms of the Oxidation of Carbon Monoxide on Ni-Doped $\alpha-Fe_2O_3$

  • Kim, Keu-Hong;Jun, Jong-Ho;Choi, Jae-Shi
    • 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.

Numerical Analysis of Transmission Characteristics on Photonic-Bandgap Structures in Millimeter Wave Band (밀리미터파 대역에서 유전체 PBG 구조의 투과 특성 해석)

  • 한진원;김기영;손종렬;태흥식
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2002.11a
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    • pp.380-383
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    • 2002
  • 본 논문에서는 20㎓~50㎓ 대역에서 2 차원 PBG(Photonic-Bandgap) 구조의 투과 특성을 RCWA(Rigorous coupled-wave analysis)방법에 의한 Transfer matrix로 해석하였다. Square lattice의 PBG 구조에 대하여 TE 편파에서 유전율의 변화와 결함(defect)의 유무에 대한 투과 특성을 고찰하였다.

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Adsorption Mechanism of Radioactive Cesium by Prussian Blue (프러시안 블루(PB)의 방사성 세슘 흡착 메커니즘 연구)

  • Jang, Sung-Chan;Kim, Jun-Yeong;Huh, Yun Suk;Roh, Changhyun
    • Journal of Radiation Industry
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    • v.9 no.3
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    • pp.127-130
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    • 2015
  • Since the accident at the Fukushima Daiichi power plant, Prussian blue (PB) has attracted increasing attention as a material for use in decontaminating the environment. We have focused the fundamental mechanism of specific $Cs^+$ adsorption into PB in order to develop high-performance PB-based $Cs^+$ adsorbents. The ability of PB to adsorb Cs varies considerably according to its origin such as what synthesis method was used, and under what conditions the PB was prepared. It has been commonly accepted that the exclusive abilities of PB to adsorb hydrated $Cs^+$ ions are caused by regular lattice spaces surrounded by cyanido-bridged metals. $Cs^+$ ions are trapped by simple physical adsorption in the regular lattice spaces of PB. $Cs^+$ ions are exclusively trapped by chemical adsorption via the hydrophilic lattice defect sites with proton-exchange from the coordination water. Prussian blue are believed to hold great promise for the clean-up of $^{137}Cs$ contaminated water around nuclear facilities and/or after nuclear accidents.

A study on electrical characteristics of ceramics capacitor for temperature compensation (온도보상용 세라믹 커패시터의 전기적 특성에 관한 연구)

  • 홍경진;정우성;김태성;이은학;이준웅
    • Electrical & Electronic Materials
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    • v.8 no.5
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    • pp.640-647
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    • 1995
  • In this study, the BaTiO$\sub$3/ capacitor add to MnO$\sub$2/ like depressor and shifter were investigated for temperature or voltage compensation by structural and electrical analysis. The relative density of BCTM, generating poly crystall and formation of lattice defect, has a 90[%] over as the CaTiO$\sub$3/ come out to control grain size. The current density of BCTM2 increased non-ohmic in high-electric field but that BCTM3 and BCTM4 had a few changing. The BCTM3 and BCTM4 unformated grain boundary shown temperature compensation properties, so that the dielectric constant was low value. The curie point was near 140[.deg. C] in BCTM1 and BCTM4, but BCTM3 and BCTM4 not shown the curie point. It is found that the charging energy of BCTM4 was changed 6[%] according to rising temperature from room temperature to 417[K]. The formation of BaMnO$\sub$3/ was low dielectric constant to change frequency and temperature.

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Image Processing and Deep Learning-based Defect Detection Theory for Sapphire Epi-Wafer in Green LED Manufacturing

  • Suk Ju Ko;Ji Woo Kim;Ji Su Woo;Sang Jeen Hong;Garam Kim
    • Journal of the Semiconductor & Display Technology
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    • v.22 no.2
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    • pp.81-86
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    • 2023
  • Recently, there has been an increased demand for light-emitting diode (LED) due to the growing emphasis on environmental protection. However, the use of GaN-based sapphire in LED manufacturing leads to the generation of defects, such as dislocations caused by lattice mismatch, which ultimately reduces the luminous efficiency of LEDs. Moreover, most inspections for LED semiconductors focus on evaluating the luminous efficiency after packaging. To address these challenges, this paper aims to detect defects at the wafer stage, which could potentially improve the manufacturing process and reduce costs. To achieve this, image processing and deep learning-based defect detection techniques for Sapphire Epi-Wafer used in Green LED manufacturing were developed and compared. Through performance evaluation of each algorithm, it was found that the deep learning approach outperformed the image processing approach in terms of detection accuracy and efficiency.

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Characterization of Lattice Thermal Conductivity in Semiconducting Materials (반도체 재료의 격자열전도도 분석)

  • Lim, Jong-Chan;Yang, Heesun;Kim, Hyun-Sik
    • Journal of the Microelectronics and Packaging Society
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    • v.27 no.4
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    • pp.61-65
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    • 2020
  • Suppressing lattice thermal conductivity of thermoelectric materials is one of the most popular approach to improve their thermoelectric performance. However, accurate characterization of suppressed lattice thermal conductivity is challenging as it can only be acquired by subtracting other contributions to thermal conductivity from the total thermal conductivity. Here we explain that electronic thermal conductivity (for all materials) and bipolar thermal conductivity (for narrow band gap materials) need to be determined accurately first to characterize the lattice thermal conductivity accurately. Methods to calculate Lorenz number for electronic thermal conductivity (via single parabolic model and using a simple equation) and bipolar thermal conductivity (via two-band model) are introduced. Accurate characterization of the lattice thermal conductivity provides a powerful tool to accurately evaluate effect of different defect engineering strategies.

A study on the identification of HPHT diamond by the photoluminescence (PL을 이용한 HPHT 처리된 다이아몬드 감별에 관한 연구)

  • 김영출;김판채
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.13 no.1
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    • pp.31-35
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    • 2003
  • The PL data bases reveal the fact that a part of lattice of HPHT treated diamond is reconfigured by the reduction, elimination, generation, and movement of vacancies and interstitials as well as of impurity elements. In particular, this very sensitive method clearly illustrated that minute amount of nitrogen impurities is present in all of these type IIa diamonds, and reveal the presence of a considerable number of point defects dispersed throughout the crystal lattice.

Dissolution of Protons in Oxides

  • Norby, Truls
    • The Korean Journal of Ceramics
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    • v.4 no.2
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    • pp.128-135
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    • 1998
  • The paper gives a brief introduction to protonic defects and their chemistry, thermodynamics and transport in oxides. The temperature dependence of the equilibrium concentration of protons is illustrated and compared for different acceptor-doped oxides. The difficulties of saturating as well as emptying the oxides of protons are discussed. In order to illustrate the possibility of lattice relaxation of defects, a conceptual study is made of a case where the enthalpy of dissolution of protons(water) at the cost of oxygen vacancies is assumed dependent on the concentration of vacancies. It is shown how this changes the behavior of hydration curves vs temperature and water vapour pressure. finally, a discussion is given on the water uptake in heavily oxygen deficient oxides; how water uptake may affect order-disorder in the oxygen sublattice and eventually lead to defective, disordered or ordered oxyhydroxides or hydroxides of potential interest as intermediate temperature proton conductions.

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Crystallinity and Internal Defect Observation of the ZnTe Thin Film Used by Opto-Electronic Sensor Material (광소자로 사용되는 ZnTe박박의 결정성에 따른 결함 관찰)

  • Kim, B.J.
    • Journal of the Korean institute of surface engineering
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    • v.35 no.5
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    • pp.289-294
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    • 2002
  • ZnTe films have been grown on (100) GaAs substrate with two representative problems. The one is lattice mismatch, the other is thermal expansion coefficients mismatch of ZnTe /GaAs. It claims here, the relationship of film thickness and defects distribution with (100) ZnTe/GaAs using hot wall epitaxy (HWE) growth was investigated by transmission electron microscopy (TEM). It analyzed on the two-sort side using TEM with cross-sectional transmission electron microscopy (XTEM) and high-resolution electron microscopy (HREM). Investigation into the nature and behavior of dislocations with dependence-thickness in (100) ZnTe/ (100) GaAs hetero-structures grown by transmission electron microscopy (TEM). This defects range from interface to 0.7 $\mu\textrm{m}$ was high density, due to the large lattice mismatch and thermal expansion coefficients. The defects of low density was range 0.7$\mu\textrm{m}$~1.8$\mu\textrm{m}$. In the thicker range than 1.8$\mu\textrm{m}$ was measured hardly defects.