• Title, Summary, Keyword: Orthorhombic-NiSi

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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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Structural Study of Interface Layers in Tetragonal-NiSi (010)/Si using Density Functional Theory (밀도범함수를 이용한 정방정계-NiSi (010)/Si 계면 층의 구조 연구)

  • Kim, Dae-Hee;Kim, Dae-Hyun;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.22 no.5
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    • pp.377-381
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    • 2009
  • Tetragonal-NiSi (010)/Si superstructures were calculated for studying the interface structure using density functional theory, The orthorhombic-NiSi was changed to the tetragonal-NiSi to be matched with the Si surface for epitaxy interface. The eight interface models were produced by the type of the Si surfaces, The tetragonal-NiSi (010)/Si (020)[00-1] superstructure was energetically the most favorable, and the interface thickness of this superstructure was the shortest among the tetragonal-NiSi (010)/Si superstructures. However, in the case of tetragonal-NiSi (010)/Si (010)[00-1] superstructure, it was energetically the most unfavorable, and the interface thickness was the longest. The energies and interface thicknesses of tetragonal-NiSi (010)/Si superstructures were influenced by the coordination number of Ni atoms and the bond length between atoms located at the interface.

Optical Properties of Photoferroelectic Semiconductors IV.(Optical Properties of SbSI:V, SbSeI:V, BiSI:V, BiSeI:V, SbSI:Cr, SbSeI:Cr, BiSI:Cr, BiSeI:Cr, SbSI:Ni, SbSeI:Ni, BiSI:Ni and BiSeI:Ni Single Crystals) (Photoferroelectric 반도체의 광학적 특성 연구 IV. (SbSI:V, SbSeI:V, BiSI:V, BiSeI:V, SbSI:Cr, SbSeI:Cr, BiSI:Cr, BiSeI:Cr, SbSI:Ni, SbSeI:Ni, BiSI:Ni 및 BiSeI:Ni 단결정의 광학적 특성에 관한 연구))

  • Oh, Seok-Kyun;Hyun, Seung-Cheol;Yun, Sang-Hyun;Kim, Wha-Tek;Kim, Hyung-Gon;Choe, Sung-Hyu;Yoon, Chang-Sun;Kwun, Sook-Il
    • Journal of the Korean Vacuum Society
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    • v.2 no.2
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    • pp.236-245
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    • 1993
  • Single crystals, SbSI : V, SbSeI : V, BiSI : V, BiSeI : V, SbSI : Cr, SbSeI : Cr, BiSI : Cr, BiSeI : Cr, SbSI : Ni, SbSeI : Ni, BiSI : Ni, and BiSeI : Ni were grown by the vertical Bridgman method. It is found that the grown single crystals have an orthorhombic structure and the indirect optical transitions. The temperature dependence of energy gap shows the two reflection point related with the phase transitions and is well fitted with Varshni equation in the continuous region. The optical absorption peaks due to the doped impurities (V, Cr and Ni) are respectively attributed to the electron transitions between the split energy levels of $V^{+2}$, $Cr^{+2}$ and $Ni^{+2}$ ions sited at $T_d$ symmetry of the host lattice.

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Structural Study of Epitaxial NiSi on Si (001) Substrate by Using Density Functional Theory (DFT) (DFT를 이용한 Si (001) 기판의 에피택시 NiSi 구조 연구)

  • Kim, Dae-Hee;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Journal of the Semiconductor & Display Technology
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    • v.6 no.4
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    • pp.65-68
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    • 2007
  • An epitaxial NiSi structure on Si (001) substrate was studied by using density functional theory (DFT). Orhorhombic and B2-NiSi structures were compared first. B2 structure was further considered as it has same crystal structure as Si and the lattice mismatch between B2 and Si is small, compared to orthorhombic-NiSi. The lattice parameters of x- and y-direction in B2-NiSi structure were modified to match with those in Si (001). The size reduction of the lattice parameter of B2-NiSi to match with that of Si increased the lattice parameter of z-direction by 10.5%. Therefore, we propose that an optimum structure of NiSi for epitaxial growth on Si (001) is a tetragonal structure.

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Improvement of Glass Forming Ability of Ni-Zr-Ti Alloys by Addition of Si and Sn

  • Lee, Jin-Kyu;Kim, Won-Tae;Kim, Do-Hyang
    • Journal of Korea Foundry Society
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    • v.23 no.5
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    • pp.286-290
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    • 2003
  • 본 연구에서는 Ni-Zr-Ti의 3원계 합금을 기본으로 하여, Si 및 Sn 등의 원소를 첨가하여 Ni-rich 영역에서 벌크 비정질 합금을 제조하였다. $Ni_{59}Zr_{20}Ti_{16}Si_2Sn_3$ 조성의 합금에서 injection casting에 의하여 약 58 K의 과냉각액상영역을 가지고 있는 직경 3 mm의 벌크 비정질 시편을 제조하였다. 이러한 우수한 비정질 형성능은 액상온도의 저하로 인해 낮은 온도까지 액상이 쉽게 과냉되기 때문인 것으로 사료된다. $Ni_{59}Zr_{20}Ti_{16}Si_5$ 합금은 두 단계에 걸쳐 결정화가 일어나는 반면, $Ni_{59}Zr_{20}Ti_{16}Si_2Sn_3$ 합금은 단일 단계에 의해 orthorhombic $Ni_{10}{(Zr,Ti)}_7$ 결정상과 cubic NiTi 결정상으로 결정화가 일어난다. 벌크 비정질 $Ni_{59}Zr_{20}Ti_{16}Si_2Sn_3$ 합금의 경우 압충강도는 2.7 GPa, 연신율은 약 2% 정도의 값을 가진다.