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Diaz-Ballester A.,CSIC - National Center of Microelectronics | Castillo-Anguera S.,CSIC - National Center of Microelectronics | Rafi J.M.,CSIC - National Center of Microelectronics | Gomez-Martinez R.,CSIC - National Center of Microelectronics | And 6 more authors.
2014 IEEE 9th IberoAmerican Congress on Sensors, IBERSENSOR 2014 - Conference Proceedings | Year: 2014

By providing a permanent electric polarization, electrets have a wide range of applications in different fields like sensors and actuators, energy harvesting or biomedicine. Stable electrets with silicon-based compatible technology are particularly pursued. In this work, different dielectric layer stacks, including SiO2, Si3N4, AL2O3 and AlN, are evaluated in terms of charge storage and retention. The corona charging characteristics are analyzed and local micro-breakdowns of the dielectric layers are observed for critical electric fields in the range of 6-7 MV/cm. A hexamethyldisilazane (HMDS) surface treatment is confirmed to provide an effective protection for electret charge retention. Unfortunately for potential applications involving liquids, the charge is found to vanish after electret surface soaking with either deionized water or ethanol. In principle, deeper charge storage in the electret dielectric layers could be achieved by using an alternative method based on charge injection by means of a direct contact. The results of first attempts with such alternative technique are also reported. © 2014 IEEE.

Elizalde E.,Campus UAB
Nuovo Cimento della Societa Italiana di Fisica C | Year: 2013

The role of the Riemann zeta function as a regularization tool is briefly review and a general scheme for the physically relevant quadratic and linear cases is discussed. The use and importance of the Chowla-Selberg series formula, together with its non-trivial extensions, to deal with situations where the spectrum is known explicitly is stressed. The derivation of such formulas is shown to rely on other fundamental expressions of mathematics, as the Poisson summation formula and Jacobi's theta function identity. Their uses in the zeta regularization of infinite quantities in quantum field theory is sketched. The second part of the paper addresses operator zeta functions, regularized traces and residues, and the multiplicative anomaly or defect of the determinant, together with potential applications. © Società Italiana di Fisica.

Del-Rosario-Calaf G.,Catalonia Institute for Energy Research IREC | Sumper A.,Catalonia Institute for Energy Research IREC | Sumper A.,Polytechnic University of Catalonia | Granados X.,Campus UAB | And 3 more authors.
Physics Procedia | Year: 2012

Electric power utilities usually use conventional grid simulators to perform simulations for grid design, operation and maintenance studies. Connection of superconducting devices, such as HTS cables, to real grids addresses the need for including specially-designed models in such studies. A 1G HTS cable user-written model suitable for dynamic simulations is developed and it is applied in a sample test grid to analyze its dynamic behavior under fault conditions. © 2011 Published by Elsevier B.V. Selection and/or peer-review under responsibility of the Guest Editors.

Herrero E.,Campus UAB | Ribas I.,Campus UAB | Jordi C.,University of Barcelona
Experimental Astronomy | Year: 2014

Stellar activity patterns are responsible for jitter effects that are observed at different timescales and amplitudes in the measurements currently obtained from photometric, spectroscopic and astrometric time series observations. These effects are usually considered just noise, and the lack of a characterization and correction strategy represents one of the main limitations for exoplanet sciences. Precise simulations of the stellar photosphere based on the most recent available models for main sequence stars can provide synthetic time series data. These may help to investigate the relation between activity jitters and stellar parameters when considering different active region patterns. Moreover, jitters can be analysed at different wavelength scales in order to design strategies to remove or minimize them from the passbands defined for specific instruments or space missions. In this work we present a model for a spotted rotating photosphere built from the contribution of a fine grid of surface elements, including all significant effects affecting the flux intensities and the wavelength of spectral features. The resulting time series data generated with this simulator are used in order to design strategies to minimize the effects of activity jitter from EChO infrared observations. An approach is presented to remove activity signals from the full infrared light curve by using the simultaneously obtained data in the visible range. Then, a similar strategy is used to correct data focused ontransit observations, and a methodology to remove the effects of non-occulted spots from transit depth measurements is presented. These procedures provide a correction of the transit data to a few times 10-5 for significantly active stars, which is within EChO noise standards. © 2014 Springer Science+Business Media Dordrecht.

Constant A.,Campus UAB | Constant A.,Montpellier University | Godignon P.,Campus UAB | Caboni A.,Campus UAB | And 2 more authors.
AIP Conference Proceedings | Year: 2010

The electrical properties of SiO2/3C-SiC structures fabricated by rapid thermal processing (RTP) using oxynitridation and hydrogenation processes have been examined. It is shown that the growth of the SiO2 films in a RTP chamber is one order of magnitude faster than in a conventional furnace. As well as being fast, this process leads to oxide films with quality comparable or even better than the one grown in classical furnaces. It is revealed that with respect to oxides grown in N2O gas, without any pre-annealing step, hydrogenation by H2 surface pre-treatment reduces the density of interface traps and effective oxide charge in SiO2 layers. The improvement in the quality of the SiO2/3C-SiC interface by H2 pre-oxidation annealing is discussed. © 2010 American Institute of Physics.

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