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Tarancon A.,CSIC - National Center of Microelectronics | Tarancon A.,Catalonia Institute for Energy Research IREC | Burriel M.,Imperial College London | Santiso J.,CIN2 | And 2 more authors.
Journal of Materials Chemistry | Year: 2010

In the context of solid oxide fuel cells (SOFCs) applications, mixed-ionic electronic conductors offer significant advantages over conventional cathodes especially in the intermediate-to-low range of temperatures where the performance of the cathode is of fundamental importance. An increasing number of layered oxide materials have been found to present excellent properties as mixed ionic-electronic conductors. Therefore, considerable efforts have been recently devoted to better understand and evaluate layered ordered structures. This article highlights the most important advances in this topic concentrating on both structural aspects and impact in cathode performance for SOFCs applications. © 2010 The Royal Society of Chemistry.

Fedorov G.,Georgetown University | Barbara P.,Georgetown University | Smirnov D.,Florida State University | Jimnez D.,Autonomous University of Barcelona | And 2 more authors.
Applied Physics Letters | Year: 2010

We have investigated the magnetic field dependence of transfer characteristics of a device fabricated in a configuration of a field-effect transistor with a conduction channel formed by a semiconducting multiwalled carbon nanotube. Our results unambiguously indicate that an axial magnetic field suppresses the band gap of the nanotube. Quantitative analysis of the data indicates linear dependence of the band gap on magnetic field as well as a linear splitting between the K and K′ subbands of the band structure of the nanotube. © 2010 American Institute of Physics.

Vandecasteele N.,University Paris Diderot | Barreiro A.,CIN2 | Barreiro A.,Technical University of Delft | Lazzeri M.,University Paris Diderot | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We report a theoretical/experimental study of current-voltage characteristics (I-V) of graphene devices near the Dirac point. The I-V can be described by a power law (I∞ Vα with 1<α≤1.5). The exponent is higher when the mobility is lower. This superlinear I-V is interpreted in terms of the interplay between Zener-Klein transport, that is tunneling between different energy bands, and defect scattering. Surprisingly, the Zener-Klein tunneling is made visible by the presence of defects. © 2010 The American Physical Society.

Alzina F.,CIN2 | Tao H.,CIN2 | Tao H.,Shanghai JiaoTong University | Moser J.,CIN2 | And 4 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2010

We have investigated the effects of ozone treatment on graphene by Raman scattering. Sequential ozone short-exposure cycles resulted in increasing the p -doping levels as inferred from the blueshift of the 2D and G peak frequencies, without introducing significant disorder. The two-phonon 2D and 2 D′ Raman peak intensities show a significant decrease while, on the contrary, the one-phonon G Raman peak intensity remains constant for the whole exposure process. The former reflects the dynamics of the photoexcited electrons (holes) and, specifically, the increase in the electron-electron-scattering rate with doping. From the ratio of 2D to 2 D′ intensities, which remains constant with doping, we could extract the ratio of electron-phonon coupling parameters. This ratio is found independent on the number of layers up to ten layers. Moreover, the rate of decrease in 2D and 2 D′ intensities with doping was found to slowdown inversely proportional to the number of graphene layers, revealing the increase in the electron-electron collision probability. © 2010 The American Physical Society.

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