• Title, Summary, Keyword: Tetragonal-NiSi

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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.

Structural Study of Tetragonal-Ni1-xPdxSi/Si (001) Using Density Functional Theory (DFT) (Density Functional Theory (DFT)를 이용한 Tetragonal-Ni1-xPdxSi/Si (001)의 구조 연구)

  • Kim, Dae-Hee;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Korean Journal of Materials Research
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    • v.18 no.9
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    • pp.482-485
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    • 2008
  • Tetragonal-$Ni_{1-x}Pd_x$Si/Si (001) structure was studied by using density functional theory (DFT). An epitaxial interface between $2{\times}2{\times}4$ (001) tetragonal-NiSi supercell and $1{\times}1{\times}2$ (001) Si supercell was first constructed by adjusting the lattice parameters of B2-NiSi structure to match those of the Si structure. We chose Ni atoms as a terminating layer of the B2-NiSi; the equilibrium gap between the tetragonal-NiSi and Si was calculated to be 1.1 ${\AA}$. The Ni atoms in the structure moved away from the original positions along the z-direction in a systematic way during the energy minimization. Two different Ni sites were identified at the interface and the bulk, respectively. The two Ni sites at the interface have 6 and 7 coordination numbers. The Ni sites with coordination number 6 at the interface were located farther away from the interface, and were more favorable for Pd substitution.

Structural Study of Tetragonal-Ni1-xMxSi/Si (001) (M = Co, Pd, Pt): First Principles Calculation (Tetragonal-Ni1-xMxSi/Si (001) (M = Co, Pd, Pt) 구조연구 : 제 1 원리계산)

  • Kim, Dae-Hee;Seo, Hwa-Il;Kim, Yeong-Cheol
    • Korean Journal of Metals and Materials
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    • v.46 no.12
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    • pp.830-834
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    • 2008
  • NiSi is currently being employed in 45 nm CMOS devices as a contact material. We employed a first principles calculation to understand the movements of atoms when Co, Pd, and Pt were added to tetragonal-NiSi on Si (001). The Ni atoms in the tetragonal-NiSi/Si (001) favored away from the original positions along positive c-direction in a systematic way during the energy minimization. Two different Ni sites were identified at the interface and the bulk, respectively. The Ni site at the interface farther away from the interface was more favorable for Pd and Pt substitution. Co, however, prafered the bulk site to the interface site, unlike Pd and Pt.

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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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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Possibility of Magnetocapacitor for Multilayered Thin Films

  • Hong, Jong-Soo;Yoon, Sung-Wook;Kim, Chul-Sung;Shim, In-Bo
    • Journal of Magnetics
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    • v.17 no.2
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    • pp.78-82
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    • 2012
  • CoNiFe(CNF)/$BaTiO_3(BTO)$/CoNiFe(CNF) multilayered thin films were deposited on Pt/Ti/$SiO_2$/Si substrates by using pulsed laser deposition (PLD) system. We fabricated three different thin films of BTO, BTO/CNF and CNF/BTO/CNF for magneto-capacitor and studied their crystalline structure, surface and interface morphology, and magnetic and electrical properties. When three different structures of multilayered thin film were compared, magnetization of CNF/BTO/CNF thin films was decreased by magnetic and dielectric interaction. Also we confirmed that capacitance of CNF/BTO/CNF multilayered thin film was enhanced as being near tetragonal structure with increasing of c/a ratio because of atomic bonding at interface between BTO dielectric and CNF magnetic materials. Finally, we studied the change of the capacitance of CNF/BTO/CNF multilayered thin film with magnetic field for emergence of magnetocapacitance and suggested a possibility of enhanced capacitance.