Silicon (Si) is currently the basis of most of our nanodevice technology and ultrathin materials based on Si would have the great advantage of easy integration into existing circuitry. Recently, it has been demonstrat...
Silicon (Si) is currently the basis of most of our nanodevice technology and ultrathin materials based on Si would have the great advantage of easy integration into existing circuitry. Recently, it has been demonstrated using molecular-dynamics calculations that two-dimensional ultrathin layered Si can be formed by cooling fluid Si confined in a slit pore [T. Morishita et al., Phys. Rev. B 77, 081401(R) (2008)]. Here we investigate, using ab initio density-functional theory, the structural and electronic properties of ultrathin double layer Si with and without hydrogenation or substitutional doping. We show that such materials have very desirable electronic properties, being able to be changed from metallic to semiconducting. They may also act as p-type or n-type semiconductors upon partial hydrogenation or substitutional doping of phosphorus. We suggest that these materials may be of great importance to production of nanoelectronic devices and sensors.
New materials and structures have been developed for efficient organic solar cells, dye-sensitized solar cells (DCSs) and organic thin-film solar cells (OPVs). In this paper, the authors discuss various strategies for...
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New materials and structures have been developed for efficient organic solar cells, dye-sensitized solar cells (DCSs) and organic thin-film solar cells (OPVs). Some strategies for achieving high photon-to-electricity ...
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New materials and structures have been developed for efficient organic solar cells, dye-sensitized solar cells (DCSs) and organic thin-film solar cells (OPVs). Some strategies for achieving high photon-to-electricity conversion efficiency in these solar cells are discussed, focusing on nanostructured materials. In the case of DSCs, unlike TiO2 nanoparticles, TiO2 nanotubes with suitable dimensions are expected to work as efficient light scatterers as well as to give large surface areas for charge separation. A strategy for designing triarylamine-functionalized ruthenium dyes, which display the high efficiency, is also proposed. Furthermore, OPVs based on donor/acceptor (D/A) block copolymers are discussed, focusing on the phase separation of donor and acceptor segments and their domain sizes.
By using the local-density approximation in density functional theory, we explore the possibility of a metallic layered compound derived from hexagonal boron nitride (h-BN). We find that the intercalation process of p...
By using the local-density approximation in density functional theory, we explore the possibility of a metallic layered compound derived from hexagonal boron nitride (h-BN). We find that the intercalation process of potassium atoms into the interlayer spacing of h-BN is exothermic with a formation energy of approximately 1.6 eV per potassium atom, and that the electronic structure of potassium-intercalated h-BN under equilibrium interlayer distance is metallic, in which electrons are injected into unoccupied, nearly-free-electron states. The calculated Fermi surfaces of the compound exhibit characteristics similar to that of graphite intercalation compounds doped with alkali/alkali-earth metals.
Vacancy-type defects in plasma immersion B-implanted Si were probed by a monoenergetic positron beam. A positron annihilates with an electron and emits two 511 keV γ-quanta. Doppler broadening spectra of the annihila...
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ISBN:
(纸本)9781424458660;9781424458691
Vacancy-type defects in plasma immersion B-implanted Si were probed by a monoenergetic positron beam. A positron annihilates with an electron and emits two 511 keV γ-quanta. Doppler broadening spectra of the annihilation radiation were measured and compared with spectra calculated using the first-principles calculations. For the as-doped sample, the vacancy-rich region was found to be localized within 0-10 nm from the surface, and the major defect species were determined to be divacancy-B complexes. After spike rapid thermal annealing at 1075°C, those complexes were annealed out, and turned to B clusters such as icosahedral B 12 distributed between 4 nm and 32 nm from the surface. We will demonstrate that that the positron annihilation technique is sensitive to point defects in shallow junctions formed on Si substrates without influence of B atoms located in the substitutional site.
We study electronic structure of the (0001) surfaces of graphite with a rhombohedral stacking arrangement by performing the first-principles total-energy calculations based on the density functional theory. We find th...
We study electronic structure of the (0001) surfaces of graphite with a rhombohedral stacking arrangement by performing the first-principles total-energy calculations based on the density functional theory. We find that ferrimagnetic spin polarization occurs on the (0001) surfaces of rhombohedral graphite. Detailed analyses of energy bands, spin densities, and wave-function distribution unequivocally reveal the nature of the ferrimagnetic spin polarization, which is associated with the peculiar surface-localized state that possesses the same characteristics as the edge-localized states of graphite flakes.
The first cluster‐based public computing for Monte Carlo simulation in Indonesia is introduced. The system has been developed to enable public to perform Monte Carlo simulation on a parallel computer through an integ...
The first cluster‐based public computing for Monte Carlo simulation in Indonesia is introduced. The system has been developed to enable public to perform Monte Carlo simulation on a parallel computer through an integrated and user friendly dynamic web interface. The beta version, so called publicMC@BATAN, has been released and implemented for internal users at the National Nuclear Energy Agency (BATAN). In this paper the concept and architecture of publicMC@BATAN are presented.
The susceptibility of four MAX phases (Ti2AlC, Cr2AlC, Ti3AlC2, and Ti3SiC2) to high-temperature thermal dissociation in vacuum has been investigated using in-situ neutron diffraction. In high vacuum, these phases dec...
The susceptibility of four MAX phases (Ti2AlC, Cr2AlC, Ti3AlC2, and Ti3SiC2) to high-temperature thermal dissociation in vacuum has been investigated using in-situ neutron diffraction. In high vacuum, these phases decomposed above 1400°C through the sublimation of M and A elements, forming a surface coating of MC. The apparent activation energies for the decomposition of sintered Ti3SiC2, Ti3AlC2, and Ti2AlC were determined to be 179.3, -71.9, and 85.7 kJ mol−1, respectively. The spontaneous release of Ti2AlC and TiC from de-intercalation during decomposition of Ti3AlC2 resulted in a negative activation energy.
We have investigated the processes of invention of PAN (Polyacrylonitrile) carbon fiber and its technology transfer to private companies. From this investigation and analysis, we have found a new R&D management mo...
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We have investigated the processes of invention of PAN (Polyacrylonitrile) carbon fiber and its technology transfer to private companies. From this investigation and analysis, we have found a new R&D management model, named "excited-oscillation model". This model suggests that both the top-down management and the personal motivation should be in phase and synergetic with each other. In this paper, the results and concept of the above model are described in detail.
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