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48 results on '"Hortelano, V."'

1. Nano-Ratchet sets free electrical power even without intentional excitation

Author

Weidlich, H., Hortelano, V., Masselink, W. T., Mahler, G., Hey, R., and Takagaki, Y.

Subjects
Physics - General Physics
Abstract

In theory ratchets enable energy harvesting by rectifying electrical fluctuations in conductors and semiconductors. Certain rectification effects in nanostructures have been demonstrated earlier. But these were not found to be usable for energy harvesting, as they were not accomplished by asymmetric transmission probabilities in the nanochannels, but rather by other secondary effects. We propose and experimentally prove a nano-ratchet effect directly linked to an asymmetry in the equilibrium transmission probability, which becomes possible when a magnetic field is present. Remarkably, the current/voltage do not disappear even without any intentional external excitation. The rectification is manifested to be highly efficient to the extent that generation of energy out of environmental electrical noises is achieved., Comment: manuscript and supplementary information

Published
2015

7. Magnetic-field-induced transport asymmetry in two-terminal circular ballistic bends.

Author

Hortelano, V., Weidlich, H., Masselink, W. T., and Takagaki, Y.

Subjects
*RECTIFICATION (Electricity), *MAGNETIC fields, *STRENGTH of materials, *ELECTRON gas, *QUANTUM mechanics
Abstract

A recent experiment [Hortelano et al., Semicond. Sci. Technol. 32, 125005 (2017)] reported a rectification effect that appeared in curved narrow ballistic channels of a two-dimensional electron gas when the strength of a magnetic field applied to the channels was tuned. The phenomenon was reproduced by classical billiard simulations as resulting from a transmission asymmetry caused by diffuse boundary scattering. However, this manifests breakdown of a commonly used simple model for diffuse boundary since the magnetic-field dependence of the transmission in two-terminal geometries has to be symmetric in equilibrium. We demonstrate here that this tendency of the system predicted by the billiard simulations is a real transmission asymmetry effect that emerges in the nonequilibrium transport. We perform nonequilibrium quantum-mechanical simulations with taking into account Coulomb repulsion. Experimental observations are presented to demonstrate consistencies with the numerical results. [ABSTRACT FROM AUTHOR]

Published
2019
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16. Influence of metal organic chemical vapour deposition growth conditions on vibrational and luminescent properties of ZnO nanorods.

Author

Montenegro, D. N., Hortelano, V., Martínez, O., Martínez-Tomas, M. C., Sallet, V., Muñoz-Sanjosé, V., and Jiménez, J.

Subjects
*METAL organic chemical vapor deposition, *CHEMICAL vapor deposition, *LUMINESCENCE, *NANORODS, *ZINC oxide
Abstract

A detailed optical characterization by means of micro Raman and cathodoluminescence spectroscopy of catalyst-free ZnO nanorods grown by atmospheric-metal organic chemical vapour deposition has been carried out. This characterization has allowed correlating the growth conditions, in particular the precursors partial-pressures and growth time, with the optical properties of nanorods. It has been shown that a high Zn supersaturation can favor the incorporation of nonradiative recombination centers, which can tentatively be associated with ZnI-related defects. Characterization of individual nanorods has evidenced that ZnI-related defects have a tendency to accumulate in the tip part of the nanorods, which present dark cathodoluminescence contrast with respect to the nanorods bottom. The effect of a ZnO buffer layer on the properties of the nanorods has been also investigated, showing that the buffer layer improves the luminescence efficiency of the ZnO nanorods, revealing a significant reduction of the concentration of nonradiative recombination centers. [ABSTRACT FROM AUTHOR]

Published
2013
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20. Composition profiles in InP/InAsP quantum well structures under the effect of reactives gases during dry etching processes — Luminescence and SIMS

Author

Landesman, Jean-Pierre, Jimenez, José, Hortelano, V., Léger, Yoan, Folliot, Herve, Delhaye, Thomas, Torres, Alfredo, Rhallabi, A., Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Fonctions Optiques pour les Technologies de l'informatiON (FOTON), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Université européenne de Bretagne - European University of Brittany (UEB)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Télécom Bretagne-Centre National de la Recherche Scientifique (CNRS), Institut des Sciences Chimiques de Rennes (ISCR), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes-Centre National de la Recherche Scientifique (CNRS), Institut des Matériaux Jean Rouxel (IMN), Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS), Institut National des Sciences Appliquées (INSA)-Université de Rennes (UNIV-RENNES)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Ecole Polytechnique de l'Université de Nantes (EPUN), Université de Nantes (UN)-Université de Nantes (UN), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Université européenne de Bretagne - European University of Brittany (UEB)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-École Nationale Supérieure des Sciences Appliquées et de Technologie (ENSSAT)-Télécom Bretagne-Centre National de la Recherche Scientifique (CNRS), Université de Rennes (UR)-Institut National des Sciences Appliquées - Rennes (INSA Rennes), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Ecole Nationale Supérieure de Chimie de Rennes (ENSCR)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Université de Nantes (UN)-Université de Nantes (UN)-Ecole Polytechnique de l'Université de Nantes (EPUN), and Université de Nantes (UN)-Université de Nantes (UN)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[PHYS.COND.CM-MS]Physics [physics]/Condensed Matter [cond-mat]/Materials Science [cond-mat.mtrl-sci], ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2014

22. Effect on Ordering of the Growth of GaInP Layers on (111)-GaAs Faces

Author

Martinez O., Hortelano V., Jimenez J., Parra V., Pelosi C., Attolini G., and Prutskij T.

Subjects
raman, luminescence, Ingap, ordering
Abstract

GaInP, an essential material for multijunction structures of III-V compounds for solar cells, can achieve better photovoltaic responses when grown on (111)GaAs faces, due to the large internal electric fields generated by the off-diagonal strain. In this work, we explored metalorganic chemical vapor deposition growth of GaInP layers on (001)-, (111)Ga-, and (111)As-GaAs substrates, using different phosphine flow rates. The structural and optical properties of the layers have been studied by micro-Raman spectroscopy, microphotoluminescence, and cathodoluminescence. Problems such as composition control, growth rate, and the presence of ordered phases are addressed.

Published
2010

24. Stresses in SiC MEMS test structures

Author

Bosi M., Attolini G., Watts B. E., Frigeri C., Rossi F., Poggi A., Roncaglia A., Mancarella F., Martinez O., and Hortelano V.

Subjects
SiC, Stress
Abstract

This work presents the growth and characterisation of b SiC films on silicon by CVD, performed in a horizontal, cold-walled reactor. Test structures of different geometries were used to determine the stresses in the film fabricated either by etching through the silicon from underneath the wafer to produce membranes or an attack from the front to reveal cantilevers. Membranes and cantilevers presented both compressive and tensile strain, depending on film thickness. The mechanisms for the cause of the strain, due to both thermal and lattice mismatch and chemical effects, are compared. The evolution of the stresses as a function of film thickness can be correlated with changes in morphology and crystal structure. For very thin films the crystal structure is highly defected as confirmed by X ray crystallography and electron microscopy. The XRD data gives ambiguous information regarding the crystallinity of the film; however, when this data was correlated with information from high resolution microscopy it was possible to interpret the diffraction data correctly. As the film becomes thicker the crystal lattice relaxes even though compressive stresses are still observed in the MEMS test structures. The use of µ-Raman spectroscopy as an auxiliary tool for assessing local stresses is also discussed.

Published
2009

47. Nanodot and nanocrystal pattern formation and luminescent properties of BiB3O6 glasses after moderate energy ion beam sputtering

Author

Plaza, J.L., Martínez, O., Hortelano, V., Bensalah, H., and Diéguez, E.

Subjects
*NANOCRYSTALS, *LUMINESCENCE, *SPUTTERING (Physics), *ARGON, *ATOMIC force microscopy, *PHOTOLUMINESCENCE measurement, *RAMAN microscopy
Abstract

Abstract: In this work we study the nanopatterning effect on the surface of BIBO glasses by means of Ion Beam Sputtering (IBS), using moderate energy (<5kV) Ar ions. The analysis, changing the energy of the Ar ions, has demonstrated the formation of nanodots, nanorripples, and nanopyramids. We have also analysed the dependence of the nanopatterns on the sample thickness for the same experimental conditions. The sizes of the nanodots have been analysed by AFM, while their optical properties studied by means of μ−Raman/μ-photoluminescence techniques. [Copyright &y& Elsevier]

Published
2012
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48. Modification of the optical and structural properties of ZnO nanowires by low-energy Ar+ ion sputtering.

Author

Allah RF, Ben T, González D, Hortelano V, Martínez O, and Plaza JL

Abstract

The effects of low-energy (≤2 kV) Ar+ irradiation on the optical and structural properties of zinc oxide (ZnO) nanowires (NWs) grown by a simple and cost-effective low-temperature technique were investigated. Both photoluminescence spectra from ZnO NW-coated films and cathodoluminescence analysis of individual ZnO NWs demonstrated obvious evidences of ultraviolet/visible luminescent enhancement with respect to irradiation fluence. Annihilation of the thinner ZnO NWs after the ion bombardment was appreciated by means of high-resolution scanning electron microscopy and transmission electron microscopy (TEM), which results in an increasing NW mean diameter for increasing irradiation fluences. Corresponding structural analysis by TEM pointed out not only significant changes in the morphology but also in the microstructure of these NWs, revealing certain radiation-sensitive behavior. The possible mechanisms accounting for the decrease of the deep-level emissions in the NWs with the increasing irradiation fluences are discussed according to their structural modifications.

Published
2013
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