Doping Dependence of Thermal Oxidation on n-type 4H-SiC

The doping dependence of dry thermal oxidation rates in n-type 4H-SiC was investigated. The oxidation was performed in the temperature range 1000C to 1200C for samples with nitrogen doping in the range of 6.5e15/cm3 to 9.3e18/cm3, showing a clear doping dependence. Samples with higher doping concentrations displayed higher oxidation rates. The results were interpreted using a modified Deal-Grove model. Linear and parabolic rate constants and activation energies were extracted. Increasing nitrogen led to an increase in linear rate constant pre-exponential factor from 10-6m/s to 10-2m/s and the parabolic rate constant pre-exponential factor from 10e9m2/s to 10e6m2/s. The increase in linear rate constant was attributed to defects from doping-induced lattice mismatch, which tend to be more reactive than bulk crystal regions. The increase in the diffusion-limited parabolic rate constant was attributed to degradation in oxide quality originating from the doping-induced lattice mismatch. This degradation was confirmed by the observation of a decrease in optical density of the grown oxide films from 1.4 to 1.24. The linear activation energy varied from 1.6eV to 2.8eV, while the parabolic activation energy varied from 2.7eV to 3.3eV, increasing with doping concentration. These increased activation energies were attributed to higher nitrogen content, leading to an increase in effective bond energy stemming from the difference in C-Si (2.82eV) and Si-N (4.26eV) binding energies. This work provides crucial information in the engineering of SiO2 dielectrics for SiC MOS structures, which typically involve regions of very different doping concentrations, and suggests that thermal oxidation at high doping concentrations in SiC may be defect mediated.Comment: 13 pages. 9 figures, accepted as a transiction in IEEE electron device. TED MS#8035

Health-related quality of life among adult HIV positive patients : assessing comprehensive themes and interrelated associations

Acknowledgements We would like to thank all HIV doctors, HIV nurses and clinical nurse specialists for their help with the inclusion of patients in the study. We are further grateful to all patients who filled out the questionnaires.Peer reviewedPublisher PD

Componentes fenólicos en aceites de oliva vírgenes monovarietales de Argelia

The high oxidative stability of virgin olive oil is related to its high monounsaturated/polyunsaturated ratio and to the presence of antioxidant compounds, such as tocopherols and phenols. In this paper, the isolation of phenolic compounds from virgin olive oil from several Algerian varieties was tested and discussed in order to know its potential uses and benefits. Quantification of phenolic and o-diphenolic substances was performed using the traditional Folin-Ciocalteau method and the sodium molybdate reaction, respectively. The qualitative and quantitative characterizations of phenolic compounds were carried out by HPLC. The experimental results show that tyrosol, hydroxytyrosol and 4-HBA (4-hydroxybenzoic acid) are the main individual phenolic compounds identified in the varieties studied. The varieties with large fruits (Grosse du Hamma, Aghenfas, Azeradj, Aguenaou, Aberkane, Bouchouk de Guergour, X-Aghenfas, Rougette de Guelma, Sigoise) are clearly distinguished from the varieties with medium-sized and small fruits by having the highest levels of individual phenolic compounds. Moreover, varieties with small fruits (Hamra, Chemlal, Boughenfas, Limli, Aimel and Mekki) presented the highest levels of oleuropein.La alta estabilidad oxidativa de los aceites de oliva vírgenes está relacionada con su alta relación de ácidos grasos monoinsaturados/poliinsaturados y con la presencia de componentes antioxidantes, como tocoferoles y polifenoles. En este trabajo se llevó acabo un aislamiento y cuantificación de compuestos fenólicos de aceites de oliva virgenes de variedades argelinas, con el fin de conocer sus potenciales usos y beneficios. La cuantificación de los componentes fenólicos y o-difenólicos se realizó por método tradicional de Folin-Ciocalteu y mediante la reacción con molibdato de sodio, respectivamente. Los compuestos fenólicos individuales cualitativos y cuantitativos en los extractos y en una mezcla estándar fueron determinados por HPLC. Los resultados experimentales muestran que el tirosol, hidroxitirosol y el 4-HBA (ácido 4-hidroxibenzoico) son los principales compuestos fenólicos individuales identificados en el conjunto de la población de las variedades estudiadas. Por otra parte, la población de las variedades con frutos grandes (Grosse du Hamma, Aghenfas, Azeradj, Aguenaou, Aberkane, Bouchouk de Guergour, X-Aghenfas, Rougette de Guelma, Sigoise) se distinguen claramente de las variedades con frutos medios y pequeños. Además, la población de variedades con frutos pequeños (Hamra, Chemlal, Boughenfas, Limli, Aimel y Mekki) presentó el nivel más alto en oleuropeína

Constructing living buildings: a review of relevant technologies for a novel application of biohybrid robotics

Biohybrid robotics takes an engineering approach to the expansion and exploitation of biological behaviours for application to automated tasks. Here, we identify the construction of living buildings and infrastructure as a high-potential application domain for biohybrid robotics, and review technological advances relevant to its future development. Construction, civil infrastructure maintenance and building occupancy in the last decades have comprised a major portion of economic production, energy consumption and carbon emissions. Integrating biological organisms into automated construction tasks and permanent building components therefore has high potential for impact. Live materials can provide several advantages over standard synthetic construction materials, including self-repair of damage, increase rather than degradation of structural performance over time, resilience to corrosive environments, support of biodiversity, and mitigation of urban heat islands. Here, we review relevant technologies, which are currently disparate. They span robotics, self-organizing systems, artificial life, construction automation, structural engineering, architecture, bioengineering, biomaterials, and molecular and cellular biology. In these disciplines, developments relevant to biohybrid construction and living buildings are in the early stages, and typically are not exchanged between disciplines. We, therefore, consider this review useful to the future development of biohybrid engineering for this highly interdisciplinary application.publishe

Plasmon-phonon coupling in large-area graphene dot and antidot arrays

Nanostructured graphene on SiO2 substrates pave the way for enhanced light-matter interactions and explorations of strong plasmon-phonon hybridization in the mid-infrared regime. Unprecedented large-area graphene nanodot and antidot optical arrays are fabricated by nanosphere lithography, with structural control down to the sub-100 nanometer regime. The interaction between graphene plasmon modes and the substrate phonons is experimentally demonstrated and structural control is used to map out the hybridization of plasmons and phonons, showing coupling energies of the order 20 meV. Our findings are further supported by theoretical calculations and numerical simulations.Comment: 7 pages including 6 figures. Supporting information is available upon request to author