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Your search keyword '"Galvão Gobato, Y."' showing total 100 results
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100 results on '"Galvão Gobato, Y."'

1. Aharonov-Bohm interference in quantum ring exciton: effects of built-in electric fields

Author

Teodoro, M. D., Campo Jr., V. L., Lopez-Richard, V., Marega Jr., E., Marques, G. E., Galvao-Gobato, Y., Iikawa, F., Brasil, M. J. S. P., AbuWaar, Z. Y., Dorogan, V. G., Mazur, Yu. I., Benamara, M., and Salamo, G. J.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

We report a comprehensive discussion of quantum interference effects due to the finite structure of excitons in quantum rings and their first experimental corroboration observed in the optical recombinations. Anomalous features that appear in the experiments are analyzed according to theoretical models that describe the modulation of the interference pattern by temperature and built-in electric fields., Comment: 6 pages, 7 figures

Published
2009
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8. Revealing the impact of strain in the optical properties of bubbles in monolayer MoSe2

Author

Covre, F. S., primary, Faria, P. E., additional, Gordo, V. O., additional, de Brito, C. Serati, additional, Zhumagulov, Y. V., additional, Teodoro, M. D., additional, Couto, O. D. D., additional, Misoguti, L., additional, Pratavieira, S., additional, Andrade, M. B., additional, Christianen, P. C. M., additional, Fabian, J., additional, Withers, F., additional, and Galvão Gobato, Y., additional

Published
2022
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19. Effects of Be acceptors on the spin polarization of carriers in p-i-n resonant tunneling diodes.

Author

Awan, I. T., Galeti, H. V. A., Galvão Gobato, Y., Brasil, M. J. S. P., Taylor, D., and Henini, M.

Subjects
BERYLLIUM, SPIN polarization, ELECTROLUMINESCENCE, RESONANT tunneling diodes, QUANTUM wells, ELECTRON paramagnetic resonance, SPINTRONICS
Abstract

In this paper, we have investigated the effect of Be acceptors on the electroluminescence and the spin polarization in GaAs/AlAs p-i-n resonant tunneling diodes. The quantum well emission comprise two main lines separated by ~20meV attributed to excitonic and Be-related transitions, which intensities show remarkably abrupt variations at critical voltages, particularly at the electron resonant peak where it shows a high-frequency bistability. The circular-polarization degree of the quantum-well electroluminescence also shows strong and abrupt variations at the critical bias voltages and it attains relatively large values (of ~–75% at 15 T). These effects may be explored to design novel devices for spintronic applications such as a high-frequency spin-oscillators. [ABSTRACT FROM AUTHOR]

Published
2014
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21. Optical properties of large area WS2 grown by chemical vapor deposition

Author

Orsi Gordo, V., Covre, F.S., Galeti, H.V.A., Galvão Gobato, Y., Henini, M., Huang, C.C., and Hewak, D.W.

Subjects
Condensed Matter::Materials Science
Abstract

Transition metal dichalcogenides (TMDs) have attracted great attention for fundamental physics and possible application as optoelectronic devices [1-5]. Monolayers of TMDs are direct gap semiconductors with optical transition in inequivalent at K and K´ valleys and distinct optical selection rules due to the combination of spin-orbit interaction and broken inversion symmetry. As a consequence, optical excitation with circularly polarized light results in circularly polarized emission. Actually, recent studies for TMDs have evidenced important valley polarization degree and large excitonics effects as well particularly at lower temperatures [1-5]. In this work, we have investigated optical properties from large are a monolayers of WS2 on 295nm SiO2/Si grown by Van der Waals Epitaxy Chemical Vapor Deposition. Particularly , we have investigated polarization resolved photoluminescence (PL ) spectra for different light excitation intensities and temperatures using a 532 nm solid state laser. The s + and s - light excitation and detection were obtained using appropriate quarter wave plates and linear polarizers. At lower temperatures, we have observed different PL peaks for the WS2 monolayer. The temperature and laser power dependence of PL spectra evidences that the observed peaks are associated to neutral (X), charged excitons (X- ) and biexcitons (XX). Therefore, our results reveal important many -body interactions in atomically thin WS2 semiconductor.

Published
2017

22. Optical and spin properties of localized and free excitons in GaBi ₓAs₁-ₓ /GaAs multiple quantum wells

Author

Balanta, M.A.G., Kopaczek, J., Orsi Gordo, V., Santos, B.H.B., Rodrigues, A.D., Galeti, H.V.A., Richards, R.D., Bastiman, F., David, J.P.R., Kudrawiec, R., and Galvão Gobato, Y.

Subjects
Condensed Matter::Materials Science, Condensed Matter::Other, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect
Abstract

Raman spectroscopy and magneto-photoluminescence measurements under high magnetic fields were used to investigate the optical and spin properties of GaBiAs/GaAs multiple quantum wells (MQWs). An anomalous negative diamagnetic energy shift was observed at higher temperatures and higher laser intensities, which was associated to a sign inversion of hole effective mass in these structures. In addition, an enhancement of the polarization degree with decreasing of laser intensity was observed (experimental condition where the emission is dominated by localized excitons). This effect was explained by changes of spin relaxation and exciton recombination times due to exciton localization by disorder.

Published
2016

23. Composition–Structure–Property Correlations in Rare-Earth-Doped Heavy Metal Oxyfluoride Glasses

Author

Doerenkamp, Carsten, Carvajal, Eduar, Magon, Claudio J., Faria, Walter J. G. J., Donoso, J. Pedro, Galvão Gobato, Y., de Camargo, Andrea S. S., and Eckert, Hellmut

Abstract

Structure–property correlations in oxyfluoride glasses have been explored in a series of lead fluoroborate and lead fluorogermanate glasses with nominal compositions (50 – x– y– z)B2O3–40PbO–y(Al2O3)–(10 + x)PbF2–zREF3and (50 – x– y)GeO2–40PbO–y(Al2O3)–(10 + x)PbF2–zREF3(x, y= 0, 10, 0 ≤ z≤ 0.5, RE = Eu, Yb). Starting from glasses with a fixed PbF2content of 10 mol %, we explore the effects of (1) increasing PbF2content to 20 mol % and (2) incorporating the intermediate oxide Al2O3at the expense of GeO2or B2O3. The emission characteristics studied on Eu-doped glasses are rationalized on the basis of structural information obtained by Raman, nuclear magnetic resonance (NMR), and pulsed electron paramagnetic resonance (EPR) spectroscopies on Yb-doped samples. In the Ge-oxyfluoride glasses, increasing PbF2content results in enhanced excited-state lifetimes of the rare-earth ions, and for this system, Eu3+emission profiles, NMR, and EPR results suggest an increased average number of fluoride ions in the first coordination sphere of the rare-earth ions. In contrast, the effect is much less apparent in the fluoroborate glasses. In both systems, Al2O3incorporation results in pronounced changes in the fluorine speciation, indicating the formation of aluminum–fluorine bonds.

Published
2024
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26. Electron and hole scattering in short-period InGaAs/InP superlattices.

Author

Pusep, Yu. A., Gold, A., Mamani, N. C., de Godoy, M. P. F., Galvão Gobato, Y., and LaPierre, R. R.

Subjects
ELECTRONS, PHOTOLUMINESCENCE, LUMINESCENCE, RELAXATION (Nuclear physics), SCATTERING (Physics)
Abstract

The combination of photoluminescence and magneto-transport measurements is used to study the single-particle relaxation time and the transport scattering time in short-period InGaAs/InP superlattices. Both the single-particle relaxation times of the electrons and of the holes were obtained in the same samples and were shown to be determined by the remote-impurity scattering. The transport scattering time for electrons was found to be dominated by the interface-roughness scattering with lateral length Λ=10 nm and height Δ = 0.13 nm. We also discuss the importance of multiple-scattering effects for small well widths and of alloy scattering for large well widths. [ABSTRACT FROM AUTHOR]

Published
2011
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27. Hole spin injection from a GaMnAs layer into GaAs–AlAs–InGaAs resonant tunneling diodes

Author

Rodrigues, D, Brasil, M, Orlita, M., Kunc, J., Galeti, H., Henini, M., Taylor, D, Galvão Gobato, Y, Laboratoire national des champs magnétiques intenses - Grenoble (LNCMI-G ), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), School of Physics [Atlanta], Georgia Institute of Technology [Atlanta], Universidade Federal de São Carlos [São Carlos] (UFSCar), and University of Nottingham, UK (UON)

Subjects
[PHYS]Physics [physics], [PHYS.COND]Physics [physics]/Condensed Matter [cond-mat], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2016

32. Magneto-optical properties of GaBiAs layers

Author

Carvalho, A R H, primary, Gordo, V Orsi, additional, Galeti, H V A, additional, Galvão Gobato, Y, additional, de Godoy, M P F, additional, Kudrawiec, R, additional, Lemine, O M, additional, and Henini, M, additional

Published
2014
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36. A comparative photoluminescence study on Mn-Free GaAs/AlAs and Mn-containing Ga 1-x Mn x As/AlAs quantum wells (QWs) grown on various orientations by MBE.

Author

Gunes, M., Erken, O., Gumus, C., Yalaz, E., Pesen, E., Ukelge, M. O., Arpapay, B., Serincan, U., Taykurt Daday, M., Galvão Gobato, Y., and Henini, M.

Subjects
PHOTOLUMINESCENCE, GALLIUM arsenide, QUANTUM wells, MOLECULAR beam epitaxy, EXCITON theory
Abstract

Optical properties of diluted magnetic semiconductor Ga0.999Mn0.001As/AlAs quantum well structures grown on (1 0 0 ), (1 1 0), (3 1 1)B and (4 1 1)B by molecular beam epitaxy are reported. Temperature-dependent spectral photoluminescence (PL) measurement was performed at temperatures between 15 and 300 K. The PL measurements showed that band gap of the alloy decreases with increasing lattice temperature regardless the growth orientations. S-shaped temperature dependence has been observed in the samples grown on (1 0 0), (3 1 1)B, (4 1 1)B orientations. PL emission energy is fitted with Varshni and Bose–Einstein Approximation to determine Debye temperature (β), (ΘE) and thermal expansion coefficient (α), the exciton–phonon coupling strength (aB). [ABSTRACT FROM AUTHOR]

Published
2016
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49. Photoinduced Enhancement of Luminescence Intensity in Poly (Vinyl Alcohol)-Poly(3-Thiopheneacetic Acid) (PVA-PTAA) Blends.

Author

Souza, J.M., Galvão, Gobato, Y., Vercik, A., and Pereira, E.C.

Subjects
*POLYMER networks, *POLYVINYL alcohol, *PHOTOLUMINESCENCE
Abstract

The photoluminescence (PL) behaviour of PVA-PTAA blends of different composition is investigated. It is observed that the interchain interaction have an important effect in this system leading to an unexpected decrease in the PL intensity as the PTAA content increase. An enhancement of the PL intensity as function of the time was also detected for all samples which were irradiated by laser. Using laser intensity of 18 W/cm 2 it was observed an increase of 93% in PVA-PTAA 1 wt% blend. Using this methodology it was possible to build an emission pattern. [ABSTRACT FROM AUTHOR]

Published
2002
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