25 results on '"Chung, Yong-An"'
Search Results
2. Ab initio investigation of interfacial layer formation in the Mo/Si boundary for extreme ultraviolet lithography.
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Kang, In-Yong and Chung, Yong-Chae
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PHYSICAL & theoretical chemistry , *CONDUCTION electrons , *ELECTRON distribution , *ELECTRONIC structure , *DENSITY functionals - Abstract
The energetics and the electronic structure of the Si/Mo(110) surface were investigated using the density functional theory calculations in an attempt to clarify the initial stage of silicide layer formation. The energy barriers for the migration of Si adatom to an adjacent hollow site passing the bridge site were calculated to be 0.64 eV [Mo (110)] and 0.74 eV [Si-substituted Mo (110)]. In order to analyze the bonding nature between Si adatom and Mo (110) surface, layer density of states and total valence electron density were obtained. It can be reasonably inferred that Mo 4d states mainly contributed to the bonding between Mo and Si and, consequently, four Mo–Si covalent bonds were formed around the Si atom at the hollow site. [ABSTRACT FROM AUTHOR]
- Published
- 2008
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3. An improved method, based on Whipple’s exact solution, for obtaining accurate grain-boundary diffusion coefficients from shallow solute concentration gradients.
- Author
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Chung, Yong-Chae and Wuensch, Bernhardt J.
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KIRKENDALL effect , *DIFFUSION - Abstract
Presents information on a study that used an equation developed by Le Claire to obtain a grain-boundary diffusion product from the measured solute concentration gradients produced under conditions of constant surface concentration in grain-boundary diffusion experiments. Whipple's solution for the solute distribution in a grain-boundary diffusion experiment; Analysis of the gradients produced by out-diffusion.
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- 1996
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4. Molecular dynamics simulation of the thin film deposition of Co/Cu(111) with Pb surfactant.
- Author
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Kim, Byung-Hyun and Chung, Yong-Chae
- Subjects
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SURFACE active agents , *THIN films , *MOLECULAR dynamics , *COBALT , *COPPER , *LEAD - Abstract
Using molecular dynamics simulation, the effect of Pb surfactant for the thin film growth of Co atoms on Cu(111) substrate was investigated. Specifically, the behavior of Co atoms being deposited on Cu(111) substrate with predeposited Pb layer was extensively investigated and compared with the case of without Pb layer to explain the effect of Pb surfactant. It was observed that Pb layer was floating during the Co deposition. It was, quantitatively, found that Pb surfactant played an important role in suppression of active diffusion of Co atoms, which was accomplished by the increase in the surface diffusion barrier energy. The energy change in the deposited Co adatom on the Cu(111) substrate with predeposited Pb layer showed that the approaching Co adatom penetrated into the Pb layer; then, the Co adatom settled down on the Cu(111) substrate. Consequently, Pb atoms around Co adatom suppressed the further diffusion of Co adatom. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
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5. Ab initio investigations on atomistic behaviors and magnetic properties in Fe–Cu multilayer system.
- Author
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Kim, Chiho and Chung, Yong-Chae
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MAGNETICS , *MAGNETIZATION , *FORCE & energy , *FUNCTIONAL analysis , *PHYSICS - Abstract
Using the density functional theory calculations, the surface diffusion and incorporation processes for Fe–Cu multilayer system were investigated. The minimum energy path calculations revealed that the hollow site of Cu(001) and Fe(001) surfaces was the most stable adsorption site, and the energy barriers for the surface diffusion were 1.04 eV for Fe/Cu(001) and 0.50 eV for Cu/Fe(001) systems. During the process, small fluctuation of magnetic moment, as amount of 0.11μB for Fe adatom and 0.02μB for Cu adatom, was observed. The energy barrier for the incorporation of the Fe adatom into the surface layer of Cu substrate was 0.75 eV, and the energy gain of the system was 0.92 eV. At the substitutional site, the magnetic moment for Fe adatom was decreased by 2.64μB. The Cu adatom required a relatively small energy barrier, 0.50 eV, for incorporation into the Fe substrate; however, it was found that, after the process, the total energy was rather increased by 0.37 eV. [ABSTRACT FROM AUTHOR]
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- 2007
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6. Surface alloy formation of Co on Al surface: Molecular dynamics simulation.
- Author
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Kim, Sang-Pil, Chung, Yong-Chae, Lee, Seung-Cheol, Lee, Kwang-Ryeol, and Lee, Kyu-Hwan
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ALLOYS , *COBALT alloys , *ALUMINUM alloys , *MOLECULAR dynamics - Abstract
Control of the interface structure of atomic scale multilayers is a fundamental issue to improve the performance of spin electronic devices. Deposition behavior of Co on Al surface at 300 K was investigated by molecular dynamics simulation. The deposited Co resulted in the formation of CoAl surface alloy regardless of the Al surface orientation. Structure of the surface alloy was dependent on the substrate orientation. Crystalline B2 structure was formed on Al (001) surface. On the contrary, amorphous mixed layers were evolved on Al (011) and (111) surfaces. In the case of Al (001) surface, 4 ML of the surface alloy were observed, which is consistent with the previous experimental observation. The present work shows that the formation of CoAl surface alloy should be considered even at the low substrate temperature and the low incident energy of deposited atoms. [ABSTRACT FROM AUTHOR]
- Published
- 2003
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7. Using Bayesian Inference for Linear Phase Log FIR Filter Design.
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Chung-Yong Chan and Goggans, Paul M.
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INFERENCE (Logic) , *BAYESIAN analysis , *IMPULSE response , *SIGNAL processing , *ATTENUATION (Physics) - Abstract
This article presents the use of the Bayesian inference framework in the design of linear-phase finite impulse-response (FIR) filter. Given a desired frequency magnitude response in dB scale and a prescribed maximum number of taps allowed in a design, the developed method automatically determines the specific taps (and their corresponding non-zero valued coefficients) required to meet the design requirements. Since the taps to be used are automatically determined, it follows that the length of the filter is also automatically determined as the filter length corresponds to the order of the last tap used. The length of the filter and the number of taps used determine the complexity of the designed filter, and the ability to design filters of complexity appropriate to the requirements is the primary advantage of using the Bayesian inference framework for filter design. To demonstrate the method, two FIR lowpass filter design problems taken from the literature are presented as examples. In these examples, the given design specifications include the passband and stopband edge frequencies, the maximum passband ripple and the minimum stopband attenuation. The obtained results demonstrate that using the Bayesian inference framework for design can yield filter designs of lower complexity than conventional design techniques while continuing to satisfy all design requirements. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
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8. Antenna Array Design as Inference.
- Author
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Goggans, Paul M. and Chan, Chung-Yong
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ANTENNA arrays , *BAYESIAN analysis , *RADIATORS , *ESTIMATION theory , *ANTENNAS (Electronics) - Abstract
This paper describes the use of the Bayesian inference framework for the design of linear antenna arrays. The principal advantage of using the Bayesian inference framework for array design is that it makes possible the automatic determination of the number of radiators required to meet given design requirements. The inference framework achieves this by making accessible to the array designer powerful computational tools developed for the simultaneous solution of parameter estimation and model selection problems. [ABSTRACT FROM AUTHOR]
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- 2008
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9. Assigning Priors for Ordered and Bounded Parameters.
- Author
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Goggans, Paul M. and Chung-Yong Chan
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DISTRIBUTION (Probability theory) , *PROBLEM solving , *PARAMETER estimation , *DENSITY functionals , *PROBABILITY theory - Abstract
In this paper, we address the problem of assigning a prior probability density function (pdf) for N parameters defined as x = {x1,x2,...,xN} that are known to be ordered and bounded. We introduce transformation functions that relate the original parameters x to new parameters u = {u1,u2,u3,...,uN} that have independent and uniform prior pdfs over the range (0,1). Results are initially derived for the three-parameter case and then extended to the N-parameter case. The transformation presented here is compared with an alternative transformation developed by Skilling. [ABSTRACT FROM AUTHOR]
- Published
- 2007
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10. Effect of nucleated Cu phase on magnetic properties and electronic structures in bcc Fe: Ab initio study.
- Author
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Choi, Heechae, Kim, Chiho, and Chung, Yong-Chae
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BODY-centered cubic metals , *IRON , *MAGNETIC properties of metals , *NUCLEATION , *COPPER , *DENSITY functionals - Abstract
Using the first-principles calculations, the change in magnetism and electronic structures during Cu nucleation in bcc Fe system was investigated. For modeling the Fe-rich bcc FeCu alloy, FexCu1-x (x≥0.75) were employed in the supercell system. Nonmagnetic Cu atoms were precipitated on the (100) plane of bcc Fe crystal, whereas the magnetized Cu atoms preferred to be precipitated on the (110) plane. Magnetization energies showed a linear decrease as the Cu concentration increased in bcc Fe. The magnetic moments of Fe atoms increased for larger concentration of Cu atoms. Electron density of states showed that the enhanced magnetic moment of Fe atoms resulted from the shift of minority spin states toward higher levels, which was associated with the bond formation between Cu and Fe atoms. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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11. Sound Decay Analysis in Acoustically Coupled Spaces Using a Re-Parameterized Decay Model.
- Author
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Goggans, Paul M., Xiang, Ning, Chan, Chung Yong, and Chi, Ying
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DECAY schemes (Radioactivity) , *ENERGY levels (Quantum mechanics) , *RADIOACTIVE decay , *ARCHITECTURAL acoustics , *PARAMETER estimation - Abstract
The sound energy decay characteristics of coupled spaces are of increasing interest to architectural acousticians. Coupled spaces occur naturally in concert halls and theaters due to the presence, for example, of balconies, orchestra pits, and stage houses. In addition, many new halls have incorporated hard chambers coupled to the primary space to achieve a flexible variation of the acoustics. In certain conditions, sound energy in these coupled spaces decays with two or more distinct exponential rate constants. The presence of multiple decay rates can have a distinct impact on a hall’s perceived acoustical quality. In previous papers we describe our initial work to apply Bayesian inferential methods to the problem of determining multiple decay times in coupled spaces using Schroeder energy decay functions derived from measured room impulse responses. In our previous work, relatively little prior information about parameters of the decay model is incorporated in the inference calculations in spite of the fact that much information regarding both the possible range of the parameters and the relationship between the parameters is known. In this paper we describe our recent efforts to incorporate this prior information into the inference calculations by re-parameterizing the multi-exponential decay model. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]
- Published
- 2004
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12. Atomic behavior of carbon atoms on a Si removed 3C-SiC (111) surface during the early stage of epitaxial graphene growth.
- Author
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Hwang, Yubin, Lee, Eung-Kwan, Choi, Heechae, Yun, Kyung-Han, Lee, Minho, and Chung, Yong-Chae
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GRAPHENE , *POLYCYCLIC aromatic hydrocarbons , *EPITAXY , *CARBON , *SEMICONDUCTORS - Abstract
The understanding of the formation of graphene at the atomic scale on Si-terminated 3C-SiC for obtaining high-quality graphene sheets remains elusive, although epitaxial graphene growth has been shown to be a well-known method for economical mass production of graphene/SiC heterojunctions. In this paper, the atomic behavior of carbon atoms on a Si removed 3C-SiC (111) surface for the formation of graphene buffer layer during the early stage of epitaxial graphene growth was investigated using a molecular dynamics simulation. Observation of the behavior of the remaining carbon atoms on the Si-terminated 3C-SiC (111) surface after removal of the silicon atoms revealed that graphene clusters, which were formed by sp2-bonded carbon atoms, start to appear at annealing temperatures higher than 1300 K. Our simulations indicated that the structural stability of the whole system increased as the number of sp2-bonded carbon atoms on the Si-terminated 3C-SiC (111) surface increased. It was also found that the diffusion energy barrier for the migration of carbon atoms from the on-top site to the bridge site on the Si-terminated 3C-SiC (111) surface mainly determines the critical temperature of graphene cluster formation. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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13. Energetics of Pb heterostructures formation on the Cu (111) in the early stage of the deposition process.
- Author
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Lee, Eung-Kwan, Choi, Heechae, Lee, Soon-Gun, and Chung, Yong-Chae
- Subjects
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HETEROSTRUCTURES , *LEAD , *MOLECULAR dynamics , *DENSITY functionals , *COPPER - Abstract
The structural and self-assembling characteristic of Pb heterostructures on the Cu (111) substrate in the early stage of the deposition process were investigated using a molecular dynamics simulation and density functional theory. The Pb islands formed on the Cu (111) surface were observed to diffuse actively in lateral directions following the layer-by-layer growth mode. A heptameric hexagonal island was found to be most stable under highly nonequilibrium conditions. This result can be explained by the tendency of Pb heterostructures, which have minimum surface energy, to have the maximum number of Pb–Pb bondings. In addition, the atomic binding energy, the surface diffusion coefficient prefactor, and the surface diffusion energy barrier for Pb adatoms were quantitatively calculated according to various shapes of Pb islands to determine the stability of the corresponding island. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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14. Geometric and magnetic properties of Co adatom decorated nitrogen-doped graphene.
- Author
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Lee, Sangho, Lee, Minho, and Chung, Yong-Chae
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MAGNETIC properties , *COBALT , *MAGNETIC properties of metals , *ADATOMS , *GRAPHENE , *SPINTRONICS - Abstract
The potential for nitrogen doped graphene with dispersed Co metal atoms as a candidate material for future spintronic applications was studied using first-principles calculations. Among the three types of defective structures, the pyridinic and pyrrolic systems were demonstrated to be structurally stable since the binding energy between the Co adatom and these substrate layers exceeded the cohesive energy of Co metal alone. Also, Co adatom on these two structures showed high magnetic moment values, which surpassed that of the Co metal bulk. From these results, it is shown that the pyridinic and pyrrolic N defects on graphene have a positive effect on the geometric stability and magnetic property of decorated Co atoms. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
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15. Ferroelectric control of magnetic anisotropy of FePt/BaTiO3 magnetoelectric heterojunction: A density functional theory study.
- Author
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Lee, Minho, Choi, Heechae, and Chung, Yong-Chae
- Subjects
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FERROELECTRICITY , *MAGNETIC anisotropy , *HETEROJUNCTIONS , *ELECTRONIC structure , *ELECTRONIC density of states - Abstract
Using ab-initio simulations, we investigated the effects of ferroelectric polarization on the magnetic anisotropy of FePt/BaTiO3 heterojunctions. The changed electronic structure at the interface of FePt and BaTiO3 reduced the magnetic anisotropy energy (MAE) under ferroelectric polarization. Through the electronic density of states analysis, it was found that the MAE change is mainly due to the changed hybridization state between d-orbitals of interface Ti and Fe atoms. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
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16. Effects of interfacial bonding in the Si-carbon nanotube nanocomposite: A molecular dynamics approach.
- Author
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Kim, Byung-Hyun, Lee, Kwang-Ryeol, Chung, Yong-Chae, and Gunn Lee, June
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INTERFACIAL bonding , *CARBON nanotubes , *NANOCOMPOSITE materials , *MOLECULAR dynamics , *NANOELECTRONICS , *ELASTICITY - Abstract
We investigated the effects of interfacial bonding on the mechanical properties in the Si-carbon nanotube (CNT) nanocomposite by a molecular dynamics approach. To describe the system appropriately, we used a hybrid potential that includes Tersoff, AIREBO (adaptive intermolecular reactive empirical bond order), and Lennard-Jones potentials. With increasing bonding strength at the interface of Si matrix and CNT, toughness as well as Young's modulus and maximum strength increased steadily. CNT pull-out and load transfer on the strong CNT were identified as the main mechanisms for the enhanced properties. At optimum bonding, crack tip was deflected around CNT and the fracture proceeded in plastic mode through Si matrix owing to the strong reinforcement of CNT, and resulted in a further enhancement of toughness. At maximum bonding, however, only load transfer is operative and the fracture returned to brittle mode. We concluded that a strong interface as long as the CNT maintains its structural integrity is desirable to realize the optimum result. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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17. Effects of biaxial strains on the magnetic properties of Co-graphene heterojunctions.
- Author
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Lee, Sangho, Choi, Heechae, and Chung, Yong-Chae
- Subjects
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GRAPHENE , *MAGNETIC moments , *ORBITAL hybridization , *ATOMS , *MAGNETIC properties - Abstract
Using the ab initio calculations, the changes of the magnetic properties of Co atoms on graphene for biaxial strains on graphene were investigated. Our calculation results showed that the compression of graphene changed the magnetic moments of Co adatoms more significantly than the elongation of graphene. From the 3d-electron density of states of Co atoms, the changes of magnetic properties of Co atoms on graphene were found to result from the significant hybridization between Co 3dyz and C 2pz orbitals. It was demonstrated that this 3d-electron hybridization of Co/graphene system originated from the strain-induced change of the local atomic structure. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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18. Electronic effect of Na on Cu(In,Ga)Se2 solar cells.
- Author
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Cho, Dae-Hyung, Lee, Kyu-Seok, Chung, Yong-Duck, Kim, Ju-Hee, Park, Soo-Jeong, and Kim, Jeha
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SOLAR cells , *ELECTRIC properties of thin films , *CONDUCTION electrons , *BAND gaps , *PHOTOVOLTAIC cells , *ELECTRIC conductivity - Abstract
We report the effect of Na on the electronic properties of Cu(In,Ga)Se2 (CIGS) thin-film solar cells with a structure of grid/ITO/i-ZnO/CdS/CIGS/Mo/SiOx/soda-lime glass (SLG). The diffusion of Na from the SLG into the CIGS layer was systematically controlled by varying the thickness of SiOx. As the Na content increased, the hole concentration of CIGS was enhanced, while the band-gap was nearly constant, which led to a lower Fermi level in the CIGS towards its valence-band edge. The Na-induced increment in the built-in potential (Vbi) across the n-(ITO/i-ZnO/CdS)/p-CIGS junction yielded an increment of open-circuit voltage that well agreed with the calculated Vbi. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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19. Preparation of Syndiotactic Poly(vinyl alcohol)/Poly(vinyl pivalate/vinyl acetate) Microspheres with Radiopacity Using Suspension Copolymerization and Saponification.
- Author
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Seok Lyoo, Won, Wook Cha, Jin, Young Kwak, Kun, Jae Lee, Young, Yong Jeon, Han, Sik Chung, Yong, and Kyun Noh, Seok
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POLYVINYL acetate , *POLYVINYL alcohol , *SUSPENSIONS (Chemistry) , *POLYMERIZATION , *MICROSPHERES , *NANOPARTICLES , *TOMOGRAPHY - Abstract
To prepare Poly(vinyl pivalate/vinyl acetate) [P(VPi/VAc)] microspheres with radiopacity, the suspension copolymerization approach in the presence of aqueous radiopaque nanoparticles was used. After, The P(VPi/VAc) microspheres with radiopacity were saponified in heterogeneous system, and then P(VPi/VAc) microspheres without aggregates were converted to s-PVA/P(VPi/VAc) microspheres of skin/core structure through the heterogeneous surface saponification. Radiopacity of microspheres was confirmed with Computed tomography (CT). [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
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20. Effects of suboxide layers on the electronic properties of Si(100)/SiO2 interfaces: Atomistic multi-scale approach.
- Author
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Kim, Byung-Hyun, Kim, Gyubong, Park, Kihoon, Shin, Mincheol, Chung, Yong-Chae, and Lee, Kwang-Ryeol
- Subjects
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SILICON research , *SILICON oxide , *INTERFACES (Physical sciences) , *ELECTRONIC structure , *MOLECULAR dynamics - Abstract
A multi-scale approach connecting the atomistic process simulations to the device-level simulations has been applied to the Si(100)/SiO2 interface system. The oxidation of Si(100) surface was simulated by the atomic level molecular dynamics, the electronic structure of the resultant Si/suboxide/SiO2 interface was then obtained by the first-principles calculations, and finally, the leakage currents through the SiO2 gate dielectric were evaluated, with the obtained interface model, by the non-equilibrium Green's function method. We have found that the suboxide layers play a significant role for the electronic properties of the interface system and hence the leakage currents through the gate dielectric. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
21. Stress evolution during the oxidation of silicon nanowires in the sub-10 nm diameter regime.
- Author
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Kim, Byung-Hyun, Ariesto Pamungkas, Mauludi, Park, Mina, Kim, Gyubong, Lee, Kwang-Ryeol, and Chung, Yong-Chae
- Subjects
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OXIDATION , *NANOWIRES , *MOLECULAR dynamics , *ATOMIC structure , *POTENTIAL energy surfaces - Abstract
Using a reactive molecular dynamics simulation, the oxidation of Si nanowires (Si-NWs) with diameters of 5, 10, and 20 nm was investigated. The compressive stress at the interface between the oxide and the Si core decreased with increasing curvature in the sub-10 nm regime of the diameter, in contrast to the theory of self-limiting oxidation where rigid mechanical constraint of the Si core was assumed. The Si core of the thinner Si-NW was deformed more with surface oxidation, resulting in a lower compressive stress at the interface. These results explain the experimental observation of full oxidation of very thin Si-NWs. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
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22. Interfacial reaction-dominated full oxidation of 5 nm diameter silicon nanowires.
- Author
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Kim, Ilsoo, Park, Tae-Eon, Lee, Ki-Young, Ha, Ryong, Kim, Byung-Hyun, Chung, Yong-Chae, Lee, Kwang-Ryeol, and Choi, Heon-Jin
- Subjects
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SILICON nanowires , *CHEMICAL vapor deposition , *NANOSTRUCTURED materials , *OXIDATION , *SEMICONDUCTOR doping - Abstract
While almost all Si nanostructures, including Si nanowires (SiNWs), Si nanocrystals, and Si nanotrench-like structures on a supra- or sub-10 nm scale exhibit self-limiting oxidative behavior, herein we report full oxidation of SiNWs 5 nm in diameter. We investigated the oxidative behavior of SiNWs with diameters of 5 nm and compared our findings with those for SiNWs with diameters of 30 nm. Single-crystalline SiNWs 5 and 30 nm in diameter were grown by a chemical vapor deposition (CVD) process using Ti as a catalyst. The SiNWs were then oxidized at 600-1000 °C for 30 min to 240 min in O2. The thicknesses of the resulting oxide layers were determined by transmission electron microscopy (TEM). As expected, the SiNWs 30 nm in underwent self-limiting oxidation that was parabolic in nature. However, under the same conditions, the SiNWs 5 nm in diameter underwent full oxidation that was linear in nature. Atomic-scale molecular dynamic simulations revealed that the compressive stress in the oxide layer, which is generated owing to the increase in the volume of the oxide formed, decreased in the case of the SiNWs 5 nm in diameter. It is likely that this decrease in the compressive stress results in a lowering of the energy barrier for the diffusion of oxygen into the oxide layer, leading to the full oxidation of the SiNWs 5 nm in diameter. It is also responsible for the oxidation in the case of SiNWs 5 nm in diameter being interfacial reaction-dominated as opposed to the diffusion dominated-oxidation typical for SiNWs. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
23. Effects of uniaxial strains on the magnetic properties and the electronic structures of Fe/graphene system: An ab initio study.
- Author
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Choi, Heechae, Lee, Eung-Kwan, Cho, Sung Beom, and Chung, Yong-Chae
- Subjects
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MAGNETIC moments , *ELECTRONIC structure , *GRAPHENE , *IRON , *ADATOMS - Abstract
Using ab initio calculations, we investigated the changes of the magnetic moment and electronic structures of Fe adatoms on strained graphene sheets. By the uniaxial tensile strains in armchair and zig-zag directions on graphene sheets, the amounts of charge transfers from graphene 2pz orbital to Fe adatom 3d orbitals were linearly increased. The magnetic moments of Fe, however, show the tendency of linear decrements with the uniaxial tensile strains. The increased Fe magnetic moments by uniaxialy graphene compressions resulted from the shifting of spin-minority states of electrons while the decreased Fe magnetic moments were due to the reduction in the spin-majority states of 3dxy-orbitals of the Fe adatom. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
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24. Surface structures and magnetic anisotropies of a Fe/Pt (001) surface: An ab initio study.
- Author
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Lee, Eung-Kwan, Choi, Heechae, Hwang, Yubin, and Chung, Yong-Chae
- Subjects
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PROPERTIES of matter , *ANISOTROPY , *CRYSTALLOGRAPHY , *PARTICLES (Nuclear physics) , *NUCLEAR physics - Abstract
Using ab initio calculations, we obtained the surface phase diagram of a Fe/Pt(001) surface and the magnetic anisotropy energies of the equilibrium Fe/Pt(001) surface structures. From the obtained surface phase diagram, Fe-rich L12 B and perpendicular L10 B were found to be the most stable Fe-Pt surface phases. The calculated magnetic anisotropy energies of the Fe-rich L12 B and perpendicular L10 B Fe/Pt(001) structures revealed that the magnetic easy axes of the surface structures prefer to align in the [001] direction. Through systematic calculations, we showed that the magnetic anisotropy reduction in Fe/Pt(001) originates from the changed electron filling in the 3dz2 orbital of Fe atoms due to the surface formation. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
25. Interface-dependent magnetic anisotropy of Fe/BaTiO3: A first principles study.
- Author
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Choi, Heechae, Hwang, Yubin, Lee, Eung-Kwan, and Chung, Yong-Chae
- Subjects
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ANISOTROPY , *PHYSICAL & theoretical chemistry , *STEREOCHEMISTRY , *MAGNETIC properties , *PROPERTIES of matter , *CONSTITUTION of matter - Abstract
Using first principles calculations, we investigated interface structure effects on the magnetic properties of the Fe/BaTiO3 system. On the BaO-terminated surface, a Fe monolayer is formed as two Fe atoms are adsorbed on the top sites of Ba and O in the (1×1) surface unit and a Fe monolayer (ML) is formed on the TiO2-terminated surface as two Fe atoms are adsorbed on the two O top sites. The magnetic anisotropy energy of Fe was higher on the TiO2-terminated surface (1.5 eV) than on the BaO-terminated surface (0.5 eV). The decomposed electron density of the states showed that the stronger hybridization of Fe with the TiO2 layer than with the BaO layer is the most important reason for the higher magnetic anisotropy energy. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
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