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김대희;김대현;서화일;김영철
- 반도체디스플레이기술학회지
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- 제7권4호
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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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Kim, Jae Il;Lee, In Gee
- Journal of Magnetics
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- 제6권3호
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- pp.80-82
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- 2001
We have investigated magnetism of $Fe_2 /Ir_4$(001) superlattice in terms of a first-principles calculation by using an all-electron full-potential linearized augmented plane-wave (FLAPW) method within the generalized gradient approximation (GGA). We considered two magnetic states, the ferromagnetic (FM) and antiferromagnetic (AFM) coupled states between the Fe layers. It was found that the FM state was energetically more stable than the AFM one by 0.166 eV. Calculated magnetic moments of the Fe layers were, in absolute values, 2.45$\mu_B$ and 2.30 $\mu_B$for the FM and AFM states, respectively. We also found that the Ir layers had very small magnetic moments less than 0.1 $\mu_B$ for both magnetic states. In all the magnetic states, the subinterface Ir layers were coupled antiferromagnetically to the interface Ir layers, while the interface Ir layers were always coupled frerromagnetically to the interface Fe layers. These results contradicted to recent experimental reports of magnetically "dead"Fe layers in Fe/Ir superlattices for which the Fe layer thickness was less than two atomic layers. We attributed that the experimentally observed "dead"Fe layers were due to possible interdiffusion between Ir and Fe layers.en Ir and Fe layers.
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김대희;서화일;김영철
- 대한금속재료학회지
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- 제46권12호
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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.
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