The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Kwang S. Kim - One of the best experts on this subject based on the ideXlab platform.
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hydrogen detachment of the hydrated hydrohalogen acids upon attaching an excess Electron
Journal of Chemical Physics, 2008Co-Authors: Han Myoung Lee, Kwang S. KimAbstract:High level ab initio calculations are employed to investigate the excess Electron attachment to the hydrated hydrohalogen acids. The excess Electron leads to the dissociation of hydrogen halide acids, which results in the release of a hydrogen radical. Neutral HCl, HBr, and HI are dissociated by tetrahydration. Upon binding an excess Electron, these hydrated hydrohalogen acids show that (i) the H–X bond strength weakens with redshifted H–X stretching frequencies, (ii) HX can have a bound-Electron State, a dissociated structure, or a zwitter-ionic structure, and (iii) HCl∕HBr is dissociated by tri/mono-hydration, while HI is dissociated even without hydration. This dissociation is in contrast to the case of Electron attachment to hydrated hydrogen fluoric acids for which HF is not dissociated by more than ten water molecules.
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novel structures for the excess Electron State of the water hexamer and the interaction forces governing the structures
Physical Review Letters, 1997Co-Authors: Sik Lee, Jongseob Kim, Sang Joo Lee, Kwang S. KimAbstract:The geometrical and Electronic structures of partially hydrated Electron systems, in particular, the water hexamer, which have been controversial for decades, have been clarified by an exhaustive search for possible low-lying energy structures. Several competing interaction forces governing the conformation have been examined for the first time. The low-lying energy structures are hybrid (or partially internal and partially surface) excess Electron States. Our prediction is evidenced from excellent agreements with available experimental data. The vertical Electron-detachment energies are mainly determined by the number of dangling H atoms $({\mathrm{H}}_{d})$.
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structure vertical Electron detachment energy and o h stretching frequencies of e h2o 12
Journal of Chemical Physics, 1997Co-Authors: Jongseob Kim, Sik Lee, Jung Mee Park, Jin Yong Lee, Kwang S. KimAbstract:The first comprehensive ab initio study is performed on an excess Electron bound to the water dodecamer to find out if this wet Electron can be regarded as a precursor of the fully solvated Electron. Various structures of the wet Electron are explored using ab initio calculations. Among a number of possible geometries categorized as unbounded, surface, internal, and partially internal excess-Electron States, the lowest-energy conformer is predicted to be a structure of a partially internal State. The predicted vertical Electron-detachment energy of this structure is in good agreement with the experimental value of Coe et al. [J. Chem. Phys. 92, 3980 (1990)]. This indicates that in the experiment the partially internal excess-Electron State structure would have been detected. The Electronic structure, interactions between the excess Electron and dangling H atoms (e⋯ H interaction), and red-shifts of the O–H stretching frequencies with strong IR intensities are discussed.
M H White - One of the best experts on this subject based on the ideXlab platform.
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an analytical retention model for sonos nonvolatile memory devices in the excess Electron State
Solid-state Electronics, 2005Co-Authors: Yu Wang, M H WhiteAbstract:We present an analytical retention model for scaled SONOS devices in the excess Electron State. In this model, trap-to-band tunneling and thermal excitation discharge mechanisms are considered to be responsible for the temperature-dependent Electron decay behaviors in SONOS devices. We assume an arbitrary trap distribution in energy within the charge-storage silicon nitride. Simulated retention characteristics are compared with experiment results measured on SONOS devices with a gate dielectric stack consisting of a 1.8 nm tunnel oxide, a 10 nm oxynitride and a 4.5 nm blocking oxide. We obtain good agreement between simulations and measurements for temperatures from 22 to 225 °C. We also extract the trap distribution in the nitride with this model. Finally, we discuss the influence of the gate dielectric properties (thickness, trap energy, etc.) and temperature on data retention of SONOS devices.
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an analytical retention model for sonos nonvolatile memory devices in the excess Electron State
International Semiconductor Device Research Symposium, 2003Co-Authors: Yu Wang, M H WhiteAbstract:For the first time, we present a SONOS retention model that incorporates both T-B and TE detrapping mechanisms. First, the influences of gate dielectric thickness, temperature and trap energy on the Electron decay are discussed, based on calculations of detrapping time constants. Next, an analytical SONOS retention model is presented, considering an arbitary trap energy distribution in the silicon nitride. Finally, the model is verified with a good agreement between measured and simulated SONOS retention characteristics at temperatures from 22/spl deg/C to 225/spl deg/C.
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charge retention of scaled sonos nonvolatile memory devices at elevated temperatures
Solid-state Electronics, 2000Co-Authors: Yang Yang, M H WhiteAbstract:Abstract The charge retention characteristics in scaled SONOS nonvolatile memory devices with an effective gate oxide thickness of 94 A and a tunnel oxide of 15 A are investigated in a temperature range from room temperature to 175°C. Electron charge decay rate is sensitive to the temperature, whereas hole charge decay rate remains essentially constant. Based on experimental observations and an amphoteric trap model for nitride traps, an analytical model for charge retention of the excess Electron State is developed. Using this thermal activated Electron retention model, the trap distribution in energy within the nitride film is extracted.
Hyoung Joon Choi - One of the best experts on this subject based on the ideXlab platform.
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low velocity anisotropic dirac fermions on the side surface of topological insulators
Physical Review B, 2011Co-Authors: Chang Youn Moon, Hyoung Joon ChoiAbstract:We report anisotropic Dirac-cone surface bands on a side-surface geometry of the topological insulator Bi$_2$Se$_3$ revealed by first-principles density-functional calculations. We find that the Electron velocity in the side-surface Dirac cone is anisotropically reduced from that in the (111)-surface Dirac cone, and the velocity is not in parallel with the wave vector {\bf k} except for {\bf k} in high-symmetry directions. The size of the Electron spin depends on the direction of {\bf k} due to anisotropic variation of the noncollinearity of the Electron State. Low-energy effective Hamiltonian is proposed for side-surface Dirac fermions, and its implications are presented including refractive transport phenomena occurring at the edges of tological insulators where different surfaces meet.
Susumu Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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interface Electronic structure at the topological insulator ferrimagnetic insulator junction
Journal of Physics: Condensed Matter, 2017Co-Authors: Y Kubota, Koichi Murata, Jun Miyawaki, Kenichi Ozawa, Mehmet C Onbasli, Tetsuroh Shirasawa, Baojie Feng, Sh Yamamoto, Roya Liu, Susumu YamamotoAbstract:An interface Electron State at the junction between a three-dimensional topological insulator film, Bi2Se3, and a ferrimagnetic insulator film, Y3Fe5O12 (YIG), was investigated by measurements of angle-resolved photoElectron spectroscopy and x-ray absorption magnetic circular dichroism. The surface State of the Bi2Se3 film was directly observed and localized 3d spin States of the Fe3+ in the YIG film were confirmed. The proximity effect is likely described in terms of the exchange interaction between the localized Fe 3d Electrons in the YIG film and delocalized Electrons of the surface and bulk States in the Bi2Se3 film.
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interface Electronic structure at the topological insulator ferrimagnetic insulator junction
arXiv: Mesoscale and Nanoscale Physics, 2016Co-Authors: Y Kubota, Koichi Murata, Jun Miyawaki, Kenichi Ozawa, Mehmet C Onbasli, Tetsuroh Shirasawa, Baojie Feng, Sh Yamamoto, Roya Liu, Susumu YamamotoAbstract:An interface Electron State at the junction between a three-dimensional topological insulator (TI) film of Bi2Se3 and a ferrimagnetic insulator film of Y3Fe5O12 (YIG) was investigated by measurements of angle-resolved photoElectron spectroscopy and X-ray absorption magnetic circular dichroism (XMCD). The surface State of the Bi2Se3 film was directly observed and localized 3d spin States of the Fe3+ State in the YIG film were confirmed. The proximity effect is likely described in terms of the exchange interaction between the localized Fe 3d Electrons in the YIG film and delocalized Electrons of the surface and bulk States in the Bi2Se3 film. The Curie temperature (TC) may be increased by reducing the amount of the interface Fe2+ ions with opposite spin direction observable as a pre-edge in the XMCD spectra.
S Poykko - One of the best experts on this subject based on the ideXlab platform.
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silicon vacancy in sic a high spin State defect
Applied Physics Letters, 1999Co-Authors: L Torpo, Risto M Nieminen, Kari Laasonen, S PoykkoAbstract:We report results from spin-polarized ab initio local spin-density calculations for the silicon vacancy (VSi) in 3C– and 2H–SiC in all its possible charge States. The calculated Electronic structure for SiC reveals the presence of a stable spin-aligned Electron-State t2 near the midgap. The neutral and doubly negative charge States of VSi in 3C–SiC are stabilized in a high-spin configuration with S=1 giving rise to a ground State, which is a many-Electron orbital singlet 3T1. For the singly negative VSi, we find a high-spin ground-State 4A2 with S=3/2. In the high-spin configuration, VSi preserves the Td symmetry. These results indicate that in neutral, singly, and doubly negative charge States a strong exchange coupling, which prefers parallel Electron spins, overcomes the Jahn–Teller energy. In other charge States, the ground State of VSi has a low-spin configuration.