Strain-dependent Optical Emission In In1 - Xgaxas/inp Quantum Wells

InGaAs/InP strained-layer modulation -doped quantum wells were studied by photoluminescence. The combination of the built-in strain and the quantum confinement in this system leads to a strong valence band mixing yielding direct and indirect band gap structures. We demonstrate that the optical emission line shape is strongly dependent on the valence band dispersion and it is a good method to distinguish between direct and indirect structures. The application of an external biaxial tensile strain to the samples provides an additional evidence of direct-to-indirect band gap transition in strained heterostructures.641515330111533014Gershoni, D., Vandenberg, J.M., Hamm, R.A., Temkin, H., Panish, M.B., (1987) Phys. Rev. B, 36, p. 1320Gershoni, D., Temkin, H., Vandenberg, J.M., Chu, S.N.G., Hamm, R.A., Panish, M.B., (1988) Phys. Rev. Lett., 60, p. 448Gershoni, D., Temkin, H., Panish, M.B., Hamm, R.A., (1989) Phys. Rev. B, 39, p. 5531Chao, C.Y.-P., Chuang, S.L., (1992) Phys. Rev. B, 46, p. 4110Sugawara, M., Okazaki, N., Fujii, T., Yamazaki, S., (1993) Phys. Rev. B, 48, p. 8102Michler, P., Hangleiter, A., Moritz, A., Fuchs, G., Härle, V., Scholz, F., (1993) Phys. Rev. B, 48, p. 111991Triques, A.L.C., Brum, J.A., (1995) Proceedings of the 22nd International Conference on the Physics of Semiconductors, Vancouver, Canada, 1994, 2, pp. 1328-1331. , edited by D.J. Lockwood (World Scientific)Weihofen, R., Weiser, G., Starck, Ch., Simes, R.J., (1995) Phys. Rev. B, 51, p. 4296Dalfors, J., Lundström, R., Holtz, P.O., Radamson, H.H., Monemar, B., Wallin, J., Landgren, G., (1997) Appl. Phys. Lett., 71, p. 503Hosea, T.J.C., Rowland, G., (1998) Supercond. Sci. Technol., 13, p. 207Tudury, H.A.P., Ribeiro, E., Iikawa, F., Brum, J.A., Bernussi, A.A., Carvalho W., Jr., Gobbi, A., unpublishedBastard, G., Brum, J.A., (1986) IEEE J. Quantum Electron., 22, p. 1625Bastard, G., (1992) Wave Mechanics Applied to Semiconductor Heterostructures, , Les Editions de Physique, ParisBaptizmanskii, V.V., Novak, I.I., Titovets, Yu.F., (1979) Sov. Phys. Solid State, 21, p. 1915Liarokapis, E., Richter, W., (1992) Meas. Sci. Technol., 3, p. 347Thewalt, M.L.W., Harrison, D.A., Reinhart, C.F., Wolk, J.A., Lafontaine, H., (1997) Phys. Rev. Lett., 79, p. 26

Assessment of the stresses produced on the bone implant/tissue interface to the different insertion angulations of the implant - a three-dimensional analysis by the finite elements method

The present study aimed to assess the stresses produced on the surface of the bone tissue around dental implants with three different insertion angulations subjected to axial and oblique loading. The study was created according to the recommendations of the Checklist for Reporting In-vitro Studies (CRIS). The Straumann? bone level RC (4.1 x 10 mm) implant, Cone Morse connection (CM), RC Straumann Variobase? with abutment (3.5 mm) was placed in the region of element 16, with the platform positioned at the height of the bone crest. Three assessment models were produced: model M1 or control - implant perpendicular to the bone crest; model M2 - implant angulated at 17° relative to the bone crest; and model M3 - implant angulated at 30° relative to the bone crest. The masticatory loads were simulated with 100 N of intensity and two loading patterns (axial and oblique) were applied to each model. Then, the models were exported to the finite elements simulation software Ansys Workbench V19.2 (Ansys Inc., Canonsburg, PA, USA). To assess the finite elements, qualitative and quantitative analyses were performed. It was observed that, under axial loading, qualitatively, the peaks occurred in the cavosurface region, palatal aspect in M1 and M2, and buccal aspect in M3. Quantitatively, the greatest angulation resulted in a low stress peak. Under oblique loading, qualitatively, the peaks occurred in the cavosurface region, buccal aspect in the three groups. Quantitatively, the greatest angulation of the implant resulted in an increase in stress peaks on the buccal aspect. Under axial loading, the three insertion angulations of the implant - M1, M2, and M3 - were clinically viable. When subjected to oblique loading, the 30° angulation (M3) suggested a significant risk of bone loss and it was contraindicated

Implant insertion angle and depth : peri-implant bone stress analysis by the finite element method

The study aimed to assess the influence of different implant insertion angles and depths on the stresses produced on the surface of peri-implant bone tissue under axial and oblique loading. The entire study followed the recommendations of the Checklist

Improving geometric road design through a virtual reality visualization technique

Traffic accidents could often be avoided with more in-depth studies of traffic and the geometric layout, using, for example, driving simulators to simulate traffic conditions. The objective of this study is to qualitatively evaluate three types of visualization techniques for examining a road project (one in a 2D printed project and the others using a driving simulator in a virtual immersion system and screen visualization). The results were evaluated by the Analytic Hierarchy Process-AHP method, used to establish different weights for the analyzed variables. For this, a questionnaire was applied to undergraduate students in Civil Engineering to compare the techniques. The results show that the immersive simulation visualization has sufficient quality and can contribute to the validation of geometric designs

Enhancement of carrier lifetimes in type-II quantum dot/quantum well hybrid structures

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORWe investigate optical transitions and carrier dynamics in hybrid structures containing type-I GaAs/AlGaAs quantum wells (QWs) and type-II GaSb/AlGaAs quantum dots (QDs). We show that the optical recombination of photocreated electrons confined in the QWs with holes in the QDs and wetting layer can be modified according to the QW/QD spatial separation. In particular, for low spacer thicknesses, the QW optical emission can be suppressed due to the transference of holes from the QW to the GaSb layer, favoring the optical recombination of spatially separated carriers, which can be useful for optical memory and solar cell applications. Time-resolved photoluminescence (PL) measurements reveal non-exponential recombination dynamics. We demonstrate that the PL transients can only be quantitatively described by considering both linear and quadratic terms of the carrier density in the bimolecular recombination approximation for type-II semiconductor nanostructures. We extract long exciton lifetimes from 700 ns to 5 mu s for QDs depending on the spacer layer thickness. Published by AIP Publishing.We investigate optical transitions and carrier dynamics in hybrid structures containing type-I GaAs/AlGaAs quantum wells (QWs) and type-II GaSb/AlGaAs quantum dots (QDs). We show that the optical recombination of photocreated electrons confined in the QWs with holes in the QDs and wetting layer can be modified according to the QW/QD spatial separation. In particular, for low spacer thicknesses, the QW optical emission can be suppressed due to the transference of holes from the QW to the GaSb layer, favoring the optical recombination of spatially separated carriers, which can be useful for optical memory and solar cell applications. Time-resolved photoluminescence (PL) measurements reveal non-exponential recombination dynamics. We demonstrate that the PL transients can only be quantitatively described by considering both linear and quadratic terms of the carrier density in the bimolecular recombination approximation for type-II semiconductor nanostructures. We extract long exciton lifetimes from 700 ns to 5 mu s for QDs depending on the spacer layer thickness.120817FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR2012/11382-9 , 2014/17141-9Sem informaçãoSem informaçã