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Your search keyword '"Sousa J"' showing total 33 results
Start Over Author "Sousa J" Journal applied physics letters
33 results on '"Sousa J"'

7. Unveiling the (De)coupling of magnetostructural transition nature in magnetocaloric R5Si2Ge2 (R = Tb, Gd) materials

Author

Pereira, A. M., primary, Kampert, E., additional, Moreira, J. M., additional, Zeitler, U., additional, Belo, J. H., additional, Magen, C., additional, Algarabel, P. A., additional, Morellon, L., additional, Ibarra, M. R., additional, Gonçalves, J. N., additional, Amaral, J. S., additional, Amaral, V. S., additional, Sousa, J. B., additional, and Araújo, J. P., additional

Published
2011
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12. Resistive switching in nanostructured thin films

Author

Silva, H., primary, Gomes, H. L., additional, Pogorelov, Yu. G., additional, Stallinga, P., additional, de Leeuw, D. M., additional, Araujo, J. P., additional, Sousa, J. B., additional, Meskers, S. C. J., additional, Kakazei, G., additional, Cardoso, S., additional, and Freitas, P. P., additional

Published
2009
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26. Understanding the role played by Fe on the tuning of magnetocaloric effect in Tb5Si2Ge2.

Author

Pereira, A. M., dos Santos, A. M., Magen, C., Sousa, J. B., Algarabel, P. A., Ren, Y., Ritter, C., Morellon, L., Ibarra, M. R., and Araújo, J. P.

Subjects
IRON, TERBIUM, SILICON, GERMANIUM, MICROSTRUCTURE, PRESSURE, PHASE transitions, THERMODYNAMICS
Abstract

In this letter, it is shown that when replacing Ge by Fe in Tb5Si2Ge2 the structural transition still occurs and enhances the magnetocaloric effect (MCE) (up to 66%) with maximum of MCE at a critical Fe amount where the magnetic and structural transitions become fully coupled. It is observed that Fe concentration is able to mimic the effect of external pressure as it induces a complex microstructure, that tunes long range strain fields. This knowledge is crucial for the development of strategies toward materials with improved performance for efficient magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]

Published
2011
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27. O2(a1Δg) production at atmospheric pressure by microdischarge.

Author

Sousa, J. Santos, Bauville, G., Lacour, B., Puech, V., Touzeau, M., and Pitchford, L. C.

Subjects
*OXYGEN, *ATMOSPHERIC pressure, *ELECTRODES, *CATHODES, *ELECTRON configuration, *GLOW discharges
Abstract

We report experimental results showing that singlet oxygen O2(a1Δg) can be efficiently produced at atmospheric pressure in a three-electrode microcathode sustained discharge (MCSD) configuration. This configuration consists of a microhollow cathode discharge (MHCD) acting as a plasma cathode to sustain a stable glow discharge between the MHCD and a third planar electrode placed at a distance of 8 mm. Experiments were performed in He/O2/NO mixtures. O2(a1Δg) number densities higher than 1016 cm-3 were measured in the MCSD afterglow at total flow rates up to 30 ln/mn, resulting in O2(a1Δg) fluxes above 10 millimole per hour (mmol/h). [ABSTRACT FROM AUTHOR]

Published
2008
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28. Dielectric mismatch effects on the electronic and optical properties of GaN/HfO2 quantum wells.

Author

Pereira, T. A. S., de Sousa, J. S., Farias, G. A., Freire, J. A. K., Degani, M. H., and Freire, V. N.

Subjects
*DIELECTRICS, *ELECTRONICS, *QUANTUM wells, *ELECTRONS, *ATOMS, *IONS, *ELECTRONIC structure
Abstract

In this work, we demonstrate that the image charges effect induced by the dielectric mismatch strongly modifies the electronic structure of GaN/HfO2 quantum wells (QWs) in such a way that the ideal QW confinement model is no longer suitable for the description of these systems. Particularly, two different confinement regimes were observed for narrow and wide QWs. In the former, electrons, light and heavy holes are spatially localized in the same region. In wide QWs, heavy holes are confined in the interfacial regions due to the strong attraction of the image charges, which does not occur for electrons and light holes. As a consequence, optical transitions involving electrons and heavy holes become less efficient in wide QWs. [ABSTRACT FROM AUTHOR]

Published
2005
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29. Gate inversion effect in Si1-xGex/HfO2/Si metal-oxide-semiconductor devices.

Author

Costa e Silva, J., de Oliveira, E. L., de Sousa, J. S., Freire, J. A. K., Freire, V. N., and Farias, G. A.

Subjects
POLYCRYSTALLINE semiconductors, SEMICONDUCTORS, POLYCRYSTALS, DIELECTRICS, OXIDES, AMORPHOUS semiconductors
Abstract

The electrical properties of polycrystalline Si1-xGex/HfO2/Si metal-oxide-semiconductor (MOS) devices are investigated theoretically by solving self-consistently the Poisson and Schrödinger equations. Our calculations demonstrate that the combination of HfO2 as dielectric film and polycrystalline gates causes charge inversion in both substrate and gate layer for ultrathin oxide layers. This effect is a consequence of the high dielectric constant of HfO2, and it is expected to occur for all high-κ-based polygated MOS devices. However, the relative doping concentration between polycrystalline gate and substrate can be used to decrease the effect of gate inversion. [ABSTRACT FROM AUTHOR]

Published
2005
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33. Understanding the role played by Fe on the tuning of magnetocaloric effect in Tb5Si2Ge2.

Author

Pereira, A. M., dos Santos, A. M., Magen, C., Sousa, J. B., Algarabel, P. A., Ren, Y., Ritter, C., Morellon, L., Ibarra, M. R., and Araújo, J. P.

Subjects
*IRON, *TERBIUM, *SILICON, *GERMANIUM, *MICROSTRUCTURE, *PRESSURE, *PHASE transitions, *THERMODYNAMICS
Abstract

In this letter, it is shown that when replacing Ge by Fe in Tb5Si2Ge2 the structural transition still occurs and enhances the magnetocaloric effect (MCE) (up to 66%) with maximum of MCE at a critical Fe amount where the magnetic and structural transitions become fully coupled. It is observed that Fe concentration is able to mimic the effect of external pressure as it induces a complex microstructure, that tunes long range strain fields. This knowledge is crucial for the development of strategies toward materials with improved performance for efficient magnetic refrigeration applications. [ABSTRACT FROM AUTHOR]

Published
2011
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