RESUMEN
Direct growth of oxide film on silicon is usually prevented by extensive diffusion or chemical reaction between silicon (Si) and oxide materials. Thermodynamic stability of binary oxides is comprehensively investigated on Si substrates and shows possibility of chemical reaction of oxide materials on Si surface. However, the thermodynamic stability does not include any crystallographic factors, which is required for epitaxial growth. Adsorption energy evaluated by total energy estimated with the density functional theory predicted the orientation of epitaxial film growth on Si surface. For lower computing cost, the adsorption energy was estimated without any structural optimization (simple total of energy method). Although the adsorption energies were different on simple ToE method, the crystal orientation of epitaxial growth showed the same direction with/without the structural optimization. The results were agreed with previous simulations including structural optimization. Magnesium oxide (MgO), as example of epitaxial film, was experimentally deposited on Si substrates and compared with the results from the adsorption evaluation. X-ray diffraction showed cubic on cubic growth [MgO(100)//Si(100) and MgO(001)//Si(001)] which agreed with the results of the adsorption energy.
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Growth morphology of carbon clusters deposited on different substrates were investigated by theoretical and experimental approach. For theoretical approach, molecular dynamics was employed to evaluate an adsorptive stability of different size of carbon clusters placed on different substrates. The adsorptive stability was estimated by the difference of total energy of supercell designed as carbon cluster placed on a certain crystal plane of substrate. Among the simulations of this study, carbon cluster flatly settled down on the surface of SrTiO[Formula: see text](001). The result was experimentally verified with layer by layer growth of graphene by pulsed laser deposition in carbon dioxide atmosphere. The absorptive stability can be useful reference for screening substrate for any target material other than graphene.
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We have investigated the structural, optical band gap, and electrical properties of (Fe2O3)0.5x:(NiO)1 - 0.5x (x = 0.3, 0.4, 0.5, 0.6 and 0.7) epitaxial thin films grown on an atomically smooth substrate at room temperature. With increasing Fe2O3 content, the rock-salt structure of the thin films transformed to a spinel structure above x = 0.6. In terms of the local structure, the increased ratio of Fe2+ ions to Fe3+ ions indicates that the octahedral sites of FeO were continuously transformed into distorted octahedral and tetrahedral sites. On the other hand, the NiO matrix was not affected by the local structure change. Chemical composition of Fe2O3:NiO affected the crystal structure, the electrical conductivity and the optical band gap of direct transition (3.35 to 2.99 eV).
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Since the discovery of graphene by sticking and peeling scotch tape off graphite, it has also been prepared by other methods, such as thermal decomposition of SiC and chemical vapor deposition (CVD) with catalytic layer. Both the exfoliation and CVD methods impose to transfer the graphene layers on other insulating substrates for device applications. We reported that diamond grows in oxygen atmosphere (Yoshimoto M.; Nature1999, 399, 340-342) in which oxidative etching and depositing carbon compete under equivalent conditions. However, oxygen atmosphere is too intense for graphite growth. Although carbon dioxide (CO2) is produced after hydrocarbon combustion, it can be a gentle and tender oxidant in certain situations. Here, we show the direct growth of graphene on insulating substrates in 100% CO2 environment and observe its layer-by-layer growth on the stepped edge of an insulating substrate. The direct growth can have a significant advantage of excluding the necessary process of transferring the graphene on the insulating substrate over other common methods.
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Cubic type room-temperature (RT) epitaxial Li0.5Ni0.5O and NiO thin films with [111] orientation grown on ultra-smooth sapphire (0001) substrates were examined using synchrotron-based thin-film X-ray diffraction. The 1[Formula: see text]1 and 2[Formula: see text]2 rocking curves including six respective equivalent reflections of the Li0.5Ni0.5O and NiO thin films were recorded. The RT B1 factor, which appears in the Debye-Waller factor, of a cubic Li0.5Ni0.5O thin film was estimated to be 1.8â (4)â Å2 from its 1[Formula: see text]1 and 2[Formula: see text]2 reflections, even though the Debye model was originally derived on the basis of one cubic element. The corresponding Debye temperature is 281â (39)â K. Furthermore, the B2 factor in the pseudo-Debye-Waller factor is proposed. This parameter, which is evaluated using one reflection, was also determined for the Li0.5Ni0.5O thin film by treating Li0.5Ni0.5O and NiO as ideal NaCl crystal structures. A structural parameter for the atomic disorder is introduced and evaluated. This parameter includes the combined effects of thermal vibration, interstitial atoms and defects caused by Li doping using the two Debye-Waller factors.
RESUMEN
Thin-film epitaxy is critical for investigating the original properties of materials. To obtain epitaxial films, careful consideration of the external conditions, i.e. single-crystal substrate, temperature, deposition pressure and fabrication method, is significantly important. In particular, selection of the single-crystal substrate is the first step towards fabrication of a high-quality film. Sapphire (single-crystalline α-Al2O3) is commonly used in industry as a thin-film crystal-growth substrate, and functional thin-film materials deposited on sapphire substrates have found industrial applications. However, while sapphire is a single crystal, two types of atomic planes exist in accordance with step height. Here we discuss the need to consider the lattice mismatch for each of the sapphire atomic layers. Furthermore, through cross-sectional transmission electron microscopy analysis, we demonstrate the uniepitaxial growth of cubic crystalline thin films on bistepped sapphire (0001) substrates.
RESUMEN
The core-level and valence-band electronic structures of LixNi1-xO epitaxial thin films with x = 0, 0.27, and 0.48 were studied by hard X-ray photoelectron spectroscopy. A double peak structure, consisting of a main peak and a shoulder peak, and a satellite structure were observed in the Ni 2p3/2 core-level spectra. The intensity ratio of the shoulder to main peak in this double peak structure increased with increasing lithium content in LixNi1-xO. This lithium doping dependence of the Ni 2p3/2 core-level spectra was investigated using an extended cluster model, which included the Zhang-Rice (ZR) doublet bound states arising from a competition between O 2p - Ni 3d hybridization and the Ni on-site Coulomb interaction. The results indicated that the change in the intensity ratio in the main peak is because of a reduction in the ZR doublet bound states from lithium substitutions. This strongly suggests that holes compensating Li doping in LixNi1-xO are of primarily ZR character.
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Non-Hodgkin lymphomas of the sinonasal region have been the subject of numerous studies. Previous reports have suggested that nasal lymphomas occurring in Orientals are mostly of the natural killer cell (NK)/T-cell phenotype which contrasts with the preponderance of the B-cell type in western populations. Recent studies indicated that NK/T-cell lymphoma constitutes the clinical condition of lethal midline granuloma. These reports led us to question whether all NK/T lymphomas are always lethal midline granuloma. We have investigated a series of 15 cases of non-Hodgkin lymphomas in the nasal and/or paranasal sinuses clinically, immunohistochemically and for the presence of Epstein-Barr virus (EBV). This study showed that the presence of EBV was common in nasal NK/T lymphoma, and this type of lymphoma was clearly highly frequent in other types of nasal lymphoma in our department. Moreover, in 4 cases of NK/T-cell lymphomas, the clinical features of lethal midline granuloma did not appear, indicating that NK/T lymphomas are not always lethal midline granuloma.
Asunto(s)
Neoplasias Óseas/patología , Neoplasias Óseas/radioterapia , Linfoma no Hodgkin/patología , Linfoma no Hodgkin/radioterapia , Paladar Duro/patología , Paladar Duro/efectos de la radiación , Neoplasias de los Senos Paranasales/patología , Neoplasias de los Senos Paranasales/radioterapia , Adulto , Anciano , Anciano de 80 o más Años , Antígenos CD20/inmunología , Neoplasias Óseas/inmunología , Complejo CD3/inmunología , Antígeno CD56/inmunología , Femenino , Humanos , Inmunohistoquímica , Hibridación in Situ , Japón , Linfoma no Hodgkin/inmunología , Masculino , Persona de Mediana Edad , Paladar Duro/inmunología , Neoplasias de los Senos Paranasales/inmunología , Dosificación RadioterapéuticaRESUMEN
We reviewed the records of 724 patients diagnosed with peritonsillar abscess who had been admitted to our hospital between January 1988 and December 1999. We analyzed their clinical features, disease course, and treatment. The male:female ratio was 3:1, and approximately two-thirds of these patients were between 20 and 39 years of age. The most common aerobic bacteria cultured from patients' pus were alpha-hemolytic streptococci. Severe complications---including deep neck infections and mediastinitis--were seen in 13 patients (1.8%). This complication rate suggests that patients with peritonsillar abscess should undergo immediate incision and drainage rather than needle aspiration.