• Title, Summary, Keyword: orthorhombic

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Study of Pd substitution in orthorhombic-NiSi/Si (010) structure: First principles calculation (Orthorhombic-NiSi/Si (010) 구조의 Pd 치환 연구: 제 1 원리 계산)

  • Kim, Dae-Hee;Kim, Dae-Hyun;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Journal of the Semiconductor & Display Technology
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    • v.7 no.4
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    • pp.41-44
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    • 2008
  • NiSi is less stable than the previously-used $CoSi_2$ at high temperature. Some noble metals, such as Pd and Pt, have been added to NiSi to improve its thermal stability. We employed a first principles calculation to understand the Pd segregation at the interface. An orthorhombic structure of NiSi was used to construct an orthorhombic-NiSi/Si (010). Lattice parameters along a- and c-axes in orthorhombic-NiSi were matched with those of Si for epitaxy contact. The optimized $1\times4\times1$ orthorhombic-NiSi (010) and $1\times2\times1$ Si (010) superstructures were put together to construct the orthorhombic-NiSi/Si (010), and the superstructure was relieved in calculation to minimize its total free energy. The optimized interface thickness of the superstructure was $1.59\AA$. Pd atom was substituted in Ni and Si sites located near interface. Both Ni and Si sites located at the interface were favorable for Pd substitution.

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Structural study of interface layers in orthorhombic-NiSi (010)/Si using density functional theory (Density Functional Theory를 이용한 orthorhombic-NiSi (010)/Si 계면 층의 구조 연구)

  • Kim, Dae-Hee;Kim, De-Hyun;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.107-108
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    • 2008
  • We calculated orthorhombic-NiSi (010)/Si superstructure. Orthorhombic-NiSi was changed to tetragonal structure to be matched with Si substrate. Eight models were produced by the type of Si substrate. In the case of orthorhombic-NiSi (010)/Si (020)[00-1], it was the most favorable energetically and the shortest of the distance between two superstructures. However, in the case of orthorhombic-NiSi (010)/Si (010)[00-1], it was the most unfavorable energetically and the longest of the distance. The energy and distance of orthorhombic-NiSi (010)/Si superstructure were changed by the coordination number of Ni atom and the bond length of atom-atom at the interface.

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Electronic Structures of Giant Magnetocaloric $Gd_5Si_2Ge_2$ Alloy

  • Rhee, Joo-Yull
    • Journal of Korean Vacuum Science & Technology
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    • v.6 no.4
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    • pp.153-157
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    • 2002
  • The electronic structures of Gd$_{5}$Si$_2$Ge$_2$ compound, which has a giant magnetocaloric effect, in the monoclinic and orthorhombic phases were calculated using the tight-binding linear-muffin-tin-orbital method within the atomic-sphere approximation. The calculated total energies of the monoclinic and orthorhombic structures in the paramagnetic phase confirm that the orthorhombic structure is more stable than monoclinic structure. The density of states (DOS) at the Fermi level of the orthorhombic phase is higher than that of the monoclinic phase in the paramagnetic phase, fulfilling the Stoner criterion. The calculated charge density verified the breaking of Ge(Si)-Ge(Si) bonding in the basal plane upon the orthorhombic-monoclinic phase transition. The DOS curve fairly well reproduces the photoemission spectrum.m.

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The Specficity of Phase Transitions of Lead Monoxide (산화납의 특이상전이)

  • 김정욱;최성철;이응상
    • Journal of the Korean Ceramic Society
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    • v.30 no.8
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    • pp.623-628
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    • 1993
  • Lead monoxide has two phases at room temperature. One is a yellow orthorhombic phase, the other is a redtetragonal phase. Sometimes two phases are hybrided. The specificity of phase transitions of lead oxide is found during the milling of the batch including lead oxide. The pure orthorhombic phase of PbO can be transformed to the tetragonal phase perfectly by wet ball milling (milling liquid is distilled water) without thermal energy. However, when ethyl alcohol, isopropyl alcohol and aceton are used as milling liquid, respectively, the hybrid form of orthorhombic andtetragonal phases is obtained by wet ball milling. From the hybrid form heat-treated at $600^{\circ}C$ for 3hrs, this work results that mechanical phase transition of orthorhombic phase make a new form as distorted type orthorhombic phase of PbO.

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Synthesis of orthorhombic $LiMnO_2$ and its electrochemical properties

  • Kim, Jung-Min;Chung, Hoon-Taek
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.15 no.2
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    • pp.51-56
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    • 2005
  • We prepared orthorhombic $LiMnO_2$ by emulsion drying method. The thermo-gravimetric measurement and X-ray diffraction studies indicated that the orthorhombic $LiMnO_2$ phase was formed above $800^{\circ}C$ by oxygen evaporation process from $LiMn_2O_4$ and $Li_2MnO_3$. In this process, we could control the ordering of $LiMnO_2$ with heating rate. It was observed that electrochemical properties depended on the ordering of this material; the ordered one exhibited good capacity retention, whereas the disordered one suffered capacity fading upon cycling, especially in the 3 V region. Transmission electron microscopic (TEM) study showed that this difference is related with difference in the stress relieving effects in the samples.

Layered $LiCo_{x}Mn_{1-x}O_{2}$ as Cathode Materials for Li-Ion Batteries

  • Kumagai, Naoaki;Myung, Seung-Taek;Komaba, Shinichi
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.7-10
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    • 2001
  • Orthorhombic type $LiCo_{x}Mn_{1-x}O_{2}$(0 ${\times}$ 0.14) oxides have been synthesized by hydrothermal treatment of $(Co_{x}Mn_{1-x})_{3}O_{4}$ precursors and LiOH aqueous solution at $170^{\circ}C$. As-synthesized powders showed well-ordered ${\beta}-NaMnO_{2}$ structures, and the products were single crystalline particle oxides from TEM observations. The particle size decreased with increasing the amount of Co substituent. Much more improved capacity upon 100 cyclings was clearly seen in orthorhombic $LiCo_{0.1}Mn_{0.9}O_{2}$, comparing to orthorhombic $LiMnO_2$.

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Layered $LiCo_{x}Mn_{1-x}O_2$ as Cathode Materials for Li-Ion Batteries

  • Kumagai, Naoaki;Myung, Seung-Taek;Komaba, Shinichi
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.7-10
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    • 2001
  • Orthorhombic type $LiCo_{x}Mn_{1-x}O_2$ (0 x 0.14) oxides have been synthesized by hydrothermal treatment of ($Co_{x}Mn_{1-x}$)$_3O_4$ precursors and LiOH aqueous solution at $170^{\circ}C$. As-synthesized powders showed well-ordered ${\beta}$-$NaMnO_2$ structures, and the products were single crystalline particle oxides from TEM observations. The particle size decreased with increasing the amount of Co substituent. Much more improved capacity upon 100 cyclings was clearly seen in orthorhombic $LiCo_{0.1}Mn_{0.9}O_2$, comparing to orthorhombic $LiMnO_2$.

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Layered $LiCo_{x}Mn_{1-x}O_2$ as Cathode Materials for Li-Ion Batteries

  • Kumagai, Naoaki;Myung, Seung-Taek;Komaba, Shinichi
    • Electrical & Electronic Materials
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    • v.14 no.12
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    • pp.7-10
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    • 2001
  • Orthorhombic type LiCo$_{x}$Mn$_{1-x}$ O$_2$(0$\leq$x$\leq$0.14) oxides have been synthesized by hydrothermal treatment of (Co$_{x}$Mn$_{1-x}$ )$_3$O$_4$precursors and LiOH aqueous solution at 17$0^{\circ}C$. As-synthesized powders showed well-ordered $\beta$-MaMnO$_2$structures, and the products were single crystalline particle oxides from TEM observations. The particle size decreased with increasing the amount of Co substituent. Much more improved capacity upon 100 cyclings was clearly seen in orthorhombic LiCo$_{0.1}$Mn$_{0.9}$O$_2$, comparing to orthorhombic LiMnO$_2$./TEX>.EX>.

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Three Kinds of Reflections with Phase Angle 0 or $\pi$ In Triclinic, Monoclinic and Orthorhombic Systems (Triclinic, Monoclinic 및 Orthorhombic Systems에서 Phase Angle 0 또는 $\pi$를 갖는 3종류의 Reflections)

  • Kim, Young-Sang;Jaejung Ko;Kang, Sang-Ook;Lee, Young-Joo;Eugene Kang;Shu, Il-Hwang
    • Korean Journal of Crystallography
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    • v.14 no.1
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    • pp.13-15
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    • 2003
  • For all primitive centric space groups in the triclinic, monoclinic and orthorhombic systems, either phase 0 or π can be allocated to three different kinds of reflections in order to specify the origin at one of the eight centers of symmetry. and the same holds for all primitive acentric space groups belonging to the point group 222. If these phased reflections are used as a basic set, more and more phased reflections with better accuracy could emerge in the process of direct methods.