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Martinez-Boubeta C.,University of Barcelona | Konstantinovic Z.,CSIC - Institute of Materials Science | Balcells L.,CSIC - Institute of Materials Science | Estrade S.,University of Barcelona | And 4 more authors.
Crystal Growth and Design | Year: 2010

In this work, the possibility to obtain epitaxial perovskite/MgO/metal multilayered heterostructures has been demonstrated by sputtering techniques. The films are ferromagnetic at room temperature, with no indication of parasite phases from X-ray diffraction and electron microscopy experiments. We argue that these improvements over most previous works may open new directions for the fabrication of fully epitaxial heterostructures for spintronics. © 2010 American Chemical Society.

Galceran R.,CSIC - Institute of Materials Science | Balcells L.,CSIC - Institute of Materials Science | Martinez-Boubeta C.,University of Barcelona | Bozzo B.,CSIC - Institute of Materials Science | And 17 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

We report on magnetotransport properties on La0.7Sr0.3MnO3/MgO/Fe tunnel junctions grown epitaxially on top of (001)-oriented SrTiO3 substrates by sputtering. It is shown that the magnetoresistive response depends critically on the MgO/Fe interfacial properties. The appearance of an FeOX layer by the interface destroys the Δ1 symmetry filtering effect of the MgO/Fe system and only a small negative tunneling magnetoresistance (TMR) (∼-3%) is measured. However, in annealed samples a switchover from positive TMR (∼+25% at 70 K) to negative TMR (∼-1%) is observed around 120 K. This change is associated with the transition from semiconducting at high T to insulating at low T taking place at the Verwey transition (TV∼120K) in Fe3O4, thus suggesting the formation of a very thin slab of magnetite at the MgO/Fe interface during annealing treatments. These results highlight the relevance of interfacial properties on the tunneling conduction process and how it can be substantially modified through appropriate interface engineering. © 2015 American Physical Society.

Dominguez-Juarez J.L.,ICFO - Institute of Photonic Sciences | MacOvez R.,ICFO - Institute of Photonic Sciences | Gonzalez M.U.,Institute Microelectronica Of Madrid Imm Cnm Csic | Martorell J.,ICFO - Institute of Photonic Sciences | Martorell J.,Polytechnic University of Catalonia
Applied Physics Letters | Year: 2010

We show that the nonlinear optical activity of an organic molecule may be quenched by electron irradiation. Exploiting this effect, we inscribe periodic χ (2) patterns in the molecular films by means of a scanning electron microscope. The second harmonic diffraction efficiency of the resulting χ (2) gratings is measured. The relative intensity of the diffraction orders observed agrees with the expectations for a sheet of nonlinear dipoles with a periodic modulation. No linear diffraction is seen. The present method allows realizing any type of two-dimensional χ (2) pattern with a resolution only limited by the electron beam patterning capabilities. © 2010 American Institute of Physics.

Martin-Sanchez J.,CSIC - Institute of Optics | Martin-Sanchez J.,Johannes Kepler University | Serna R.,Institute Microelectronica Of Madrid Imm Cnm Csic | Toudert J.,CSIC - Institute of Optics | And 3 more authors.
Optics Letters | Year: 2014

The potential of Ge nanoparticles (NPs) embedded in Al2O 3 with tunable effective optical bandgap values in the range of 1.0-3.3 eV to induce enhanced Er3+ light emission is investigated. We demonstrate nonresonant indirect excitation of the Er3+ ions mediated by the Ge NPs at room temperature. Efficient Er3+ light emission enhancement is obtained for Ge NPs with large effective optical bandgaps in the range of 1.85 to 2.8 eV. The coupled Ge NP-Er emission shows a negligible thermal quenching from 10 K to room temperature that is related to Er3+ de-excitation through thermally activated defect states. © 2014 Optical Society of America.

Kyoung Ryu Y.,CSIC - Institute of Materials Science | Aitor Postigo P.,Institute Microelectronica Of Madrid Imm Cnm Csic | Garcia F.,Institute Microelectronica Of Madrid Imm Cnm Csic | Garcia R.,CSIC - Institute of Materials Science
Applied Physics Letters | Year: 2014

Silicon nanowires are key elements to fabricate very sensitive mechanical and electronic devices. We provide a method to fabricate sub-12 nm silicon nanowires in thickness by combining oxidation scanning probe lithography and anisotropic dry etching. Extremely thin oxide masks (0.3-1.1 nm) are transferred into nanowires of 2-12 nm in thickness. The width ratio between the mask and the silicon nanowire is close to one which implies that the nanowire width is controlled by the feature size of the nanolithography. This method enables the fabrication of very small single silicon nanowires with cross-sections below 100 nm2. Those values are the smallest obtained with a top-down lithography method. © 2014 AIP Publishing LLC.

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