• Journal of the Korean Ceramic Society
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• v.46 no.4
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• pp.425-428
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• 2009

We performed a density functional theory study to investigate the interaction of DEMS (diethoxymethylsilane) with the H-terminated Si (001) surface. The optimum structure of DEMS was first calculated by a first principles study. The dissociation probability of the O-C bond of DEMS was higher than the other seven bonds based on the bond energy calculation. When the fragmented DEMS groups reacted with the H-terminated Si (001) surface, it was the most favorable among the eight reactions to form a bond between the Si atom on the surface and the O atom of a fragmented DEMS group (($C_2H_5O$)Si($CH_3$)(H)-O-) by forming a $C_2H_6$ as by-product.

• Proceedings of the Korean Vacuum Society Conference
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• 2002.02a
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• pp.71-71
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• 2002

• Journal of the Korean Vacuum Society
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• v.14 no.2
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• pp.97-102
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• 2005

NO adsorption can be used in synthesizing oxynitride thin films which have potential application in nanodevices. However, it is very difficult to understand the oxynitridation Process since too many factors are involved in it. In this paper, we present our first-principles molecular dynamics calculation of the NO molecule adsorption on the Si(001) surface as the initial stage of the oxynitridation process. The previous first-principles calculation has argued the NO molecule is dissociated with a very small activation barrier, 0.07eV, which acutally corresponds to 1.60eV considering thermodynamics. This is in clear contrast to the observation that NO is dissociated at temperatures as low as 20K From extensive searches of NO on the Si(001) surface, we have found the new dissociation processes that have the much lower activation energies, less than 0.01 eV. We also present the dissociation and penetration processes with the corresponding activation energies and discuss their experimental implications.

• Proceedings of the Korean Magnestics Society Conference
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• 2009.12a
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• pp.72-73
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• 2009

First-principles calculations were carried out to investigate the effects of Al impurities on bcc Fe magnetism by considering SOC. No significant solid solution hardening effect was found. Albeit the effects of the SOC by Al on spin magnetic moments were minor, there are sizeable orbital magnetic effects. It is concluded that the orbital magnetism due to the Al impurity is strongly related with the impurity screening of the system as seen in Si impurity case [3], but the effects of Al impurity is stronger than those of Si impurity in terms of orbital magnetism.

• Korean Journal of Materials Research
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• v.26 no.1
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• pp.42-46
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• 2016

The properties of zinc oxynitride semiconductors and their associated thin film transistors are studied. Reactively sputtered zinc oxynitride films exhibit n-type conduction, and nitrogen-rich compositions result in relatively high electron mobility. Nitrogen vacancies are anticipated to act as shallow electron donors, as their calculated formation energy is lowest among the possible types of point defects. The carrier density can be reduced by substituting zinc with metals such as gallium or aluminum, which form stronger bonds with nitrogen than zinc does. The electrical properties of gallium-doped zinc oxynitride thin films and their respective devices demonstrate the carrier suppression effect accordingly.

• Journal of Magnetics
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• v.14 no.1
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• pp.1-6
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• 2009

The magnetic properties of ${Bi_x}{Ca_{1-x}}{MnO_3}$ for x = 0.12, 0.13, 0.14, 0.15, and 0.16 were examined by measuring magnetic susceptibility, resistivity and electron magnetic resonance at different temperatures. ${Bi_x}{Ca_{1-x}}{MnO_3}$ showed complicated magnetic structure that varies with temperature and composition, particularly around Bi composition x. 0.15. The aim of this study was to determine how the magnetic and physical properties of ${Bi_x}{Ca_{1-x}}{MnO_3}$ change in this region. In addition, first principles calculations of the magnetic phase of ${Bi_x}{Ca_{1-x}}{MnO_3}$ for x = 0, 0.125, 0.25 were carried out, and the spin state, electric and magnetic characteristics are discussed.

• Journal of Magnetics
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• v.4 no.4
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• pp.107-110
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• 1999

In order to investigate the magnetism of Ru submonolayer on Pb(001), we have performed first-principles calculations for half-layer of Ru on Pd(001) using the full-potential linearzed augmented plane wave (FLAPW) method. We have found that the magnetic moment of Ru for 0.5 layer is 2.21 B. It is found that substrate Pd layers are polarized by the 0.5 Ru overlayer to have significant magnetic moments. Our results are compared with those obtained by the anomalous Hall effect. The calculated electronic structures, i,e., the spin densities and density of states are presented and discussed in relation with magnetic properties.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.373-376
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• 2016

Transition metal dichalcogenides (TMDs) such as $MoS_2$ is the thinnest semiconductor, exhibits promising prospects in the applications of optoelectronics, catalysis and hydrogen storage devices. Uniform and high quality $MoS_2$ is highly desirable in large area for its applications on commercial scale and fundamental research. Many experimental techniques i.e CVD have been developed to successfully synthesis $MoS_2$ on large scale, here in this work atomistic detail to understand the growth mechanism is addressed which was greatly overlooked. Here based on first principles calculation we found that polarity of seeding promter (crystal violet considerd in this work) controls the growth mechanism. It is also found that molybdenum destroys the precursor while sulfur adsorption with precursor is favorable.

• Journal of the Korean Magnetics Society
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• v.18 no.6
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• pp.201-205
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• 2008

In order to investigate the origin of the band gap in the half-metallic Heusler alloy, $Co_2MnSi$, through the electronic structure calculation, we have calculated the electronic structures for the compounds consisted of parts of Heusler structures, i.e. zinc-blende CoMn, half-Heusler CoMnSi, and artificial $Co_2Mn$, using the full-potential first-principles band calculation method. By investigating the band hybridization and energy gap for the calculated density of states for these compounds, we found that the the origin of the band gap is not consistent with the explanation discussed by Galanakis et al. We have also discussed the magnetism for these compounds by the calculated number of majority- and minority-spin electrons.

• Journal of the Korean Chemical Society
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• v.17 no.6
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• pp.395-405
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• 1973

By use of an Integral Hellmann-Feynman formula, the cubic crystal field splitting 1O Dq in $KNiF_3$ is calculated from first principles. Numerical values of covalency parameters and necessary integrals are quoted from Sugano and Shulman. The result, 7100$cm^{-1}$, is in excellent agreement with the observed value, 7250$cm^{-1}$. It is found that higher order perturbation energy correction is of the same order of magnitude as 10 Dq itself and is, therefore, essential tin calculating 10 Dq from first principles. It is also found that the point charge potential is the dominant part of the crystal field potential.