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Trabajo presentado en el XXX International Materials Research Congress and International Converence on Advanced Materials, celebrado en Cancún (México), del 14 al 19 de agosto de 2022

Trabajo presentado en el 2nd Iberian Thermoelectric Workshop (ITW2019), celebrado en Ciudad Real (España), del 5 al 6 de septiembre de 2019, Nowadays, the research to find semiconducting materials for energy conversion applications has raised a huge interest in the scientific community. Particularly, a high number of investigations are focused to find suitable compounds for thermoelectric applications[1]. In this work, we report a detailed investigation about the deposition of 4 different Cu-Se chalcogenides films (amorphous CuSe, hexagonal CuSe, cubic Cu7Se4, cubic Cu2Se) on flexible polycarbonate substrates by using PHRMS, a novel semiconductor thin film deposition technique developed in our lab that allows the growth at room temperature (RT) and in a few minutes of many metal selenides (Ag-Se, Cu-Se, Sn-Se, …) with different compositions[2,3]. The obtained films were characterized by X-ray diffraction (XRD), energy dispersive analysis of X-ray (EDX) and scanning electron microscopy (SEM-FEG). The transport properties (Seebeck coefficient, resistivity and mobility carriers) were measured from room temperature up to 100ºC. All the four compounds investigated show p-type conductivity with different values of the Seebeck coefficient (ranging from +10V/K to +450V/K), resistivities measured at RT from 10-4 to 100 cm and a maximum power factor (PF) of the order of 0.15mWm-1K-2.

Trabajo presentado en el International Conference on Thermoelectricity (ICT), celebrado en Caen (Francia), del 1 al 5 de julio de 2018

Trabajo presentado en el E-MRS Spring Meeting and Exhibit, celebrado en Estrasburgo (Francia), del 22 al 26 de mayo de 2017, It has been reported crystalline p-type Cu2Se bulk material has been synthesized with excellent thermoelectric properties with a unusual combination of properties leads to an ideal thermoelectric material within the new concept of `Phonon-liquid electron-crystal¿ [1]. We report a novel approach on the growth of highly efficient thermoelectric materials via pulse controlled reactive magnetron sputtering. This technique allows for a finer control of the stoichiometry, crystallographic orientation, etc. and it is a very fast production technique. It is shown to be fully reproducible and scalable to industry. The fabrication method is a low temperature process, and thus allows the use of organic and/or flexible substrates to deposit the films on them, which opens a whole new field of applications that are not possible with other fabrication techniques. We have focused in the deposit of Cu2-xSe and Ag2-xSe films, obtaining high values in the power factor (1.1 mW¿m-1¿ K-2) for the cubic ß-Cu2Se phase and (2.5 mW¿m-1¿ K-2) for the cubic ß-Ag2Se phase compared with the highest reported in the literature for both bulk and higher than films. [1] H. Liu et al., Nature Materials 11, 422 (2012).

Photovoltaic (PV) technology is dominated today by crystalline silicon (c-Si) technology. Thinfilm technology based on Cu(In,Ga)Se2 (CIGS) absorbers is currently the most-efficient polycrystalline alternative [1]. PV modules with CIGS are very effective in converting light directly into electricity, and, at the same time, can be produced on flexible and lightweight supports. CIGS can be used also in tandem devices that will enable impressive efficiency values well beyond 30%.

Trabajo presentado en el Nanotechnology Colombia-U.S. Workshop, celebrado en Bogotá (Colombia), los días 14 y 15 de febrero de 2017, Scanning thermal microscopy (SThM) has been implemented as a prominent technique that simultaneously measure topography and 3-omega voltage (3¿¿SThM); using a commercial probe of Pd coated on SiN at the end of the tip, it is possible to reach a lateral spatial resolution better than 100 nm [1]. The thermal images obtained with the 3¿ method are related to the heat variations of the samples due to their thermal conductivity [2]. Its characteristics make of this scanning probe a very important technique for nanoscale thermal transport investigations, which have a wide applicability in areas from biomedical, electronic industry and nano-device, solar cells among others[3]. This powerful technique is also of great interest for thermal conductivity measurements in thermoelectric materials. Actually, copper selenide Cu2Se and silver selenide Ag2Se have a promising efficiency although some issue regarding copper seggegation must be studied. Due to that copper segregation the thermal properties of these materials are highly affected. This segregation seems to occur as nanoparticle so it is interesting to see the effect at the nanoscale. However, the thermal conductivity measurements at the nanoscale are very challenging and some of the current thermal methods have spatial resolution issues, which makes the evaluation even more difficult in the case of these nanostructured materials [4]. Here, we describe the calibration work and the considerations needed to extract information of the SThM images of Cu2Se (fig.1). The contact potential difference obtained by kelvin probe force microscopy (KPFM) and the SThM measures of Ag2Se (fig. 2) are also discussed in this work.

Trabajo presentado en la NanoSpain Conference, celebrada en Logroño (España), del 15 al 18 de marzo de 2016, The current interest in thermoelectric materials (TE) focuses on its ability to transform a temperature difference in a voltage difference (Seebeck effect). Similarly to the creation of a temperature difference due to an electric voltage (Peltier effect), it is possible to use them as heat sources and sinks in industrial applications as an alternative cooling medium and cooling. [1] The main advantages of thermoelectric devices over other cooling systems - compression systems - is a more reliable usage time by not having moving parts, non-use of greenhouse gases and the absence of vibration due they are solid state devices with reduced size becoming very efficient in local applications. Increasing the efficiency of a thermoelectric material necessitates increasing the figure of merit, usually called zT . The zT is composed of three material’s parameters as well as the absolute temperature T. zT =( S2 )κ -1 in which S is the Seebeck coefficient,  is the electrical conductivity, and      e p is the thermal conductivity (  e and  p are the electron and phonon contributions respectively.[2] The TE performance is maximized by realizing excellent electrical transport and poor heat conduction in solid materials. The n-type Ag2+xSe and p-type Cu2+xSe has promising thermoelectric properties. Previous investigations on Ag2Se report that it has high electrical conductivity and low thermal conductivity and that it zT approaches 1 at room temperature. [3] The reported zT increases as temperature increases from 70 K to room temperature. This is especially encouraging because Ag2Se becomes a superionic conductor around 407 K, as does Cu2Se, which has been reported to have a zT that increases with temperature to 1.5 at 1000 K. [4] Report a new approach in manufacture of highly efficient thermoelectric via reactive sputtering. This new manufacturing technology allows to control the stoichiometry of the samples, the crystallographic orientation and thermoelectric properties. It is fully reproducible and scalable to the industry today. In Figure 1 it is shown as morphology is influenced depending these stoichiometries changes.

Trabajo presentado en la 14th European Conference on Thermoelectrics (ECT2016), celebrada en Lisboa (Portugal), del 20 al 23 de septiembre de 2016

Comunicación presentada en la 3rd International Meeting for Researchers in Materials and Plasma Technology (IMRMPT), celebrada en Bucaramanga (Colombia) del 4 al 9 de mayo de 2015., [ES] En la investigación de procesos de fabricación de películas delgadas de nuevos materiales semiconductores y nano-estructuras multicapa para células fotovoltaicas entre otras aplicaciones, se requieren sistemas de deposición por sputtering reactivo que garanticen, por una parte, la ausencia de impurezas o contaminantes no intencionales durante el depósito de las películas e intercaras y por otra, la posibilidad de secuenciar procesos sucesivos diferentes sin romper el vacío y escalar posteriormente tales procesos a una fabricación industrial in line de dispositivos completos. Estos sistemas tienen además que incorporar técnicas de caracterización y control in-situ, para asegurar la reproducibilidad y el análisis de los puntos críticos de los procesos. Sobre la base de la experiencia previa de los autores, en el campo de la tecnología MBE multicámara y sistemas de sputtering UHV, se presentan diversos ejemplos concretos de aplicación a la fabricación de diferentes dispositivos: Células solares de QDs en semiconductores III-V, detectores superconductores para telescopios de Rayos X en el espacio, actuadores magnetoestrictivos para microscopía AFM en líquidos y multicapas para células CIGS y seleniuros para dispositivos termoeléctricos., [EN] Research on thin film manufacturing processes of novel semiconductor materials, and nanostructured multilayers for photovoltaic solar cells and other applications, requires specific reactive sputtering deposition systems to ensure, on the one hand , the absence of unintentional impurities or cross contaminants during film and interfaces growth. Moreover, these systems will require the ability to sequence successive processes without breaking vacuum and then scaling such processes to in-line industrial manufacturing of complete devices. Also, to ensure reproducibility and analysis of critical points of the process, they might need to incorporate in-situ characterization and control techniques. Based on the previous experience of the authors in the field of MBE technology and multi UHV sputtering systems, concrete examples of application to the manufacture of different devices are presented: QDs solar cells in III-V semiconductors, superconductor detectors for X-ray telescopes in space, magnetostrictive actuators for AFM microscopy in liquids, multilayers for CIGS cells and novel selenide based thermoelectric devices.

Comunicación presentada en la 3rd International Meeting for Researchers in Materials and Plasma Technology (IMRMPT), celebrada en Bucaramanga (Colombia) del 4 al 9 de mayo de 2015., [EN] Recent studies predict a four times larger global economy that today employ 80% more energy in 2050. Currently about 2% of the electricity produced in a conventional power plant is harvested, the rest is lost as heat in the central and transport processes. It is in this context that recovers important renewable energy and increasing efficiency. Semiconductor Materials may be an alternative to such industrial challenges. Recent advances for nanodevices present Silicon Germanium as thermoelectric materials heat recovery nanostructures at high temperatures and Aluminum Nitride as a substrate for piezoelectric devices used as Sensors Acoustic Wave (SAW). Piezoelectric injectors may help to control it more precisely the injection times and the amount of fuel that is inserted into the combustion engine helping to reduce fuel consumption on the other hand vehicles. For recover the energy lost as heat making electricity with a thermoelectric generator could save up to 10% in fuel consumption., [ES] Recent studies predict a four times larger global economy that today employ 80% more energy in 2050. Currently about 2% of the electricity produced in a conventional power plant is harvested, the rest is lost as heat in the central and transport processes. It is in this context that recovers important renewable energy and increasing efficiency. Semiconductor Materials may be an alternative to such industrial challenges. Recent advances for nanodevices present Silicon Germanium as thermoelectric materials heat recovery nanostructures at high temperatures and Aluminum Nitride as a substrate for piezoelectric devices used as Sensors Acoustic Wave (SAW). Piezoelectric injectors may help to control it more precisely the injection times and the amount of fuel that is inserted into the combustion engine helping to reduce fuel consumption on the other hand vehicles. For recover the energy lost as heat making electricity with a thermoelectric generator could save up to 10% in fuel consumption.

Ponencia presentada en las IV Jornadas de Jóvenes Investigadores, celebradas en Madrid el 9 de julio de 2015., El actual interés en los materiales termoeléctricos se centra en su capacidad de transformar una diferencia de temperatura en una diferencia de Voltaje (efecto Seebeck). Igualmente a la creación de una diferencia de temperatura debida a un voltaje eléctrico (efecto Peltier), siendo posible utilizarlos como fuentes y sumideros de calor en aplicaciones industriales como un medio alternativo de refrigeración y enfriamiento. Entre las principales ventajas de los dispositivos termoeléctricos sobre los demás sistemas de refrigeración ¿ sistemas de compresión ¿ se encuentra una mayor fiabilidad en el tiempo de uso al no contar con partes móviles, la no utilización de gases de efecto invernadero y la ausencia de vibración debido a que son dispositivos de estado sólido con un tamaño reducido llegando a ser muy eficientes en aplicaciones locales.

Póster presentado en la 12th European Conference on Thermoelectrics (ECT2014), celebrada en Madrid del 24 al 26 de septiembre de 2014., Si1-XGeX alloys are widely known thermoelectric materials showing a very high figure of merit at high temperatures, and have been used for long time in different applications. The control of the crystal structure of the material has been demonstrated as a key point on the thermoelectric properties. Sputtering deposition of Si1-XGeX at room temperature gives rise to amorphous material, with very low electric conductivity and hence bad thermoelectric properties. In order to produce crystalline thin films, sputter deposition at high temperature is usually performed, but the high temperatures needed can produce a reduction of the dopant concentration, hence reducing the electric conductivity. Crystallization of amorphous SiGe (a-SiGe) is performed by heating at temperatures over 625ºC during 24 h or more. However, it was shown that metal-induced crystallization (MIC) is a promising technology for reducing crystallization temperature of a-Si, a-Ge and a-SiGe. There are many metals, such as Al, Au, Ag and Ni, that can be used for performing MIC. In spite of the low crystallization temperatures in the above processes of MIC, there were serious problems of metal contamination of the SiGe films. In this paper, we report our works concerning crystallization of Si0.8Ge0.2 thin films using Au as crystallization catalyzer. We selected Au thin film since the eutectic temperatures for Au-Si (363 ºC) and Au-Ge systems (361 ºC) are very close. Post-deposition thermal treatments in inert atmosphere show that crystallization temperature is reduced to about 350 ºC, whit treatment times as short as 1 hour. Moreover, in situ crystallization during the deposition of SiGe over gold is also demonstrated at temperatures over 350 ºC. It shall also be noted that gold acts as a crystallization catalyzer, and can be easily eliminated by chemical methods, as it does not incorporate into the material structure. The crystallized thin films show high Seebeck coefficient and low electric resistance.

Póster presentado en la 12th European Conference on Thermoelectricity (ECT2014), celebrada en Madrid del 24 al 26 de septiembre de 2014., Copper selenides have recently attracted the attention of the thermoelectric community due to their high figure of merit at high temperatures (ZT¿1.6 @ 1000 K), and the existence of a crystallographic phase transition at T ¿400K at which ZT can reach values as high as 2.3. The materials have been usually prepared by solid state reaction methods, taking about a week to produce a singe sample. In this work we show a reactive sputtering method that allows the production of samples in times of some minutes, with well controlled stoichiometry and high crystallinity., This work has been financed by project: Nano-structured High-efficiency Thermo-Electric Converters (nanoHITEC). J. A.FPI grant from MINECO. Pérez aknowledges

Las células solares de banda intermedia se inventaron en España. Constituyen una propuesta para aumentar la eficiencia de las células solares por encima del límite de Shockley y Queisser para células de un solo gap. El número de ideas para llevarlas a la práctica (desde la utilización de puntos cuánticos a la implantación selectiva de impurezas) se ha ido expandiendo a medida que nuestra comprensión ha ido aumentando. En este artículo repasamos el concepto de célula solar de banda intermedia y algunas de estas ideas para llevarla a la práctica.

Póster presentado en el Congreso Fuerzas y Tunel, celebrado en San Lorenzo de El Escorial del 12 al 14 de septiembre de 2012., Kelvin probe force microscopy ( KPFM) is a powerful atomic force microscope (AFM)-based technique to meas ure the local variations of surface potential at the nanoscale. It operates by detecting the difference of the work function between a fixed substrate and a conducting movable probe. By modulating the applied potent ial on the probe until the electric force between sample and tip is extinguish ed, it is possible to deter mine the local potential of the surface. KPFM has been extensively us ed to characterize the electrical properties of a wide variety of samples, from semiconductors to biomolecules. As KPFM spatial resolution is intrin sically limited by the long range of the electrostatic interaction, many contri butions on this technique are aimed to improve this feature. Some of them include operating in high vacuum and the development of specialized probes to operate in ambient conditions as, for example, the use of carbon nanotubes or coaxial AFM probes that are electrically shielded everywhere exc ept the very end of the tip. Here we present the use of standar d silicon tips modified by the deposition of gold nanoparticl es. These tips have recent ly shown to improve the aspect ratios and spatial resolution of AFM images. The silicon tips are modified by deposition of nan oclusters of nominal diam eter of 2-3 nm under ultrahigh vacuum conditions using an ion cluster source. In an attempt to extend this enhancement of the resolution and sensitivity to the electrical measurements under ambient conditions, we have performed a KPFM analysis of several samples that include Au and Ag nanoparticles , graphene flakes on silicon dioxide, single-wall carbon nanotubes and double-stranded DNA molecules. The results are compared with similar measurements performed with conventional metallic tips (PtIr5 coated tips). We show that both, topography and surface potent ial images present evid ent improvements when recorded with Au-nanoparticle modified tips

Trabajo presentado a la "31st International Conference on the Physics of Semiconductors" celebrada en Zurich (Suiza) del 29 de julio al 3 de Agosto de 2012., Epitaxial quantum dot (QD) solar cells need tens if not hundreds of QD layers in order to have an appreciable absorption at long wavelengths. In the InAs/GaAs system, due to the larger covalent radius of InAs, increasing the number and stack density of QDs layers inevitably leads to an increase of the strain fields and eventually to the formation of dislocations. The strain balanced (SB) technique consists of compensating the compressive stress introduced by the QDs by a tensile stress in the spacer between layers. In this way, by alternating tensile-compressive regions, the strain in the material is minimized and the formation of dislocations is retarded. Several groups have implemented their own combinations of materials in an attempt to stack many layers of QDs, either using P or N compounds. We have used this technique before to stack 50 InAs quantum dot layers in a solar cell structure with improved crystal quality and optical properties. In this work, we report on the fabrication and optical characterization of InAs quantum posts (QPs) grown using the above approximation in the limit of negligible spacer layer thickness. In order to achieve proper balancing of the accumulated stress, the growth of the samples was characterized by in situ real-time measurements of the total accumulated stress during growth. This technique allows us to monitor the accumulated compressive stress arising from the InAs layer and the tensile stress introduced by the compensating layer (GaAsP of different compositions). The resulting InAs/GaAsP quantum posts (QPs) are 120-nm-long vertical nanostructures which show a record height/diameter aspect ratio >7.4 We have embedded these nanostructures in a p-i-n diode structure to investigate their electro-optical properties as a function of temperature and applied bias. Our study reveals weak localization of carriers along the QP vertical axis at low excitation power and a one-dimensional-like density of states at high excitation.

The lack of materials able to withstand the severe radiation conditions (high thermal loads and atomistic damage) expected in fusion reactors is the actual bottle neck for fusion to become a reality. The main requisite for plasma facing materials (PFM) is to have excellent structural stability since severe cracking or mass loss would hamper their protection role which turns out to be unacceptable. Additional practical requirements for plasma facing materials are among others: (i) high thermal shock resistance, (ii) high thermal conductivity (iii) high melting point (iv) low physical and chemical sputtering, and (v) low tritium retention.

La invención se refiere a un procedimiento de deposición de calcogenuros con control de la presión de gas mediante activación pulsada y continua de una válvula en la fuente de gas calcógeno. Gracias a la aplicación de estos pulsos se puede controlar la presión en la cámara de manera que la estequiometría es fácilmente controlable, mientras que se puede prescindir de válvulas complicadas., Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, Cosnejo Superior de Investigaciones Científicas (España), A1 Solicitud de patente con informe sobre el estado de la técnica

Trabajo presentado a la: "European Conference on Applied Superconductivity (EUCAS)" celebrada del 18 al 23 de septiembre de 2011 en Holanda., We report on the sensitivity of the superconducting critical temperature (TC) to layer thickness, as well as on TC reproducibility in Mo/Au bilayers. Resistivity measurements on samples with a fixed Au thickness (dAu) and Mo thickness (dMo) ranging from 50 to 250 nm, and with a fixed dMo and different dAu thickness are shown. Experimental data are discussed in the framework of Martinis model, whose application to samples with dAu above their coherence length is analysed in detail. Results show a good coupling between normal and superconducting layers and excellent TC reproducibility, allowing to accurately correlate Mo layer thickness and bilayer TC., This work has been carried out with financial support from the Spanish MICINN (projects ESP2006‐13608‐C02, AYA2008‐00591/ESP, MAT2008‐01077/NAN and MAT2009‐13977C03). MPB and OG would like to thank Spanish Education Ministry for a FPU grant and a FPI grant.

We report on the fabrication details of TES based on Mo/Au bilayers. The Mo layer is deposited by radio frequency (RF) sputtering and capped with a sputter deposited thin Au protection layer. Afterwards, a second Au layer of suitable (lower) resistivity is deposited ex‐situ by e‐beam evaporation, until completion of the total desired Au thickness. The deposition was performed at room temperature (RT) on LPCVD Si3 N4 membranes. Such a deposition procedure is very reproducible and allow controlling the critical temperature (Tc) and normal electrical resistance (RN ) of the Mo/Au bilayer. The process is optimized to achieve low stress bilayers, thus avoiding the undesirable curvature of the membranes. Bilayers are patterned using photolithographic techniques and wet etching procedures. Mo superconducting paths are used to contact the Mo/Au bilayers, thus ensuring good electrical conductivity and thermal isolation. The entire fabrication process let to stable and reproducible sensors with required and tunable functional properties

Trabajo presentado al 16th European Molecular Beam Epitaxy Workshop celebrado en Alpe d'Huez (Francia) del 20 al 23 de Marzo de 2011.

Trabajo presentado en el Nanomaterials for Energy and Environmental Applications, celebrado en España en abril de 2010

Trabajo presentado a NanoSpain 2010 celebrado en Málaga del 23-26 Marzo, 2010, The development during the last decade of the Atomic Force Microscopy (AFM) technique focused on biological systems, has initiated a new form of biomolecular physics since this technique has introduced a new approach to the study biological processes. This success is largely due to the emergence of dynamic modes operated in physiological environments. Herein we present a novel cantilever mechanical excitation technique based on the magnetostrictive effect [1] that exhibits important advantages with respect to other methods. Commercial silicon nitride cantilevers were sputtered on the opposite side of the tip with magnetostrictive and soft magnetic thin iron-boron-nitrogen films. This amorphous magnetic alloy presents excellent magnetic properties [2], good corrosion resistance in liquid environments, and nearly zero deposition induced stress [3] for optimized sputtering parameters. In the presence of an alternating magnetic field the coated top side of the cantilever periodically extends, thus generating a mechanical oscillatory movement on the cantilever. This new actuation mode can be operated in physiological environments, lacks the unwanted heating of tip and/or sample, avoiding thermal drift problems. It also exhibits high resolution and stability, low noise and compatibility with the use of an inverted optical microscope. As an operational example we present low noise and high resolution topographic images acquired in liquid environment to demonstrate the method capability

Trabajo presentado en la International Conference on the physics of semiconductors, celebrado en Seúl (República de Corea), del 25 al 30 de julio de 2010, We have studied the lateral coupling between InAs/GaAs quantum dot pairs embedded in a field-effect structure. Quantum dot pairs and molecules have been identified by the correlated evolution of the Coulomb blockade features of each QD in the pair. This behaviour is largely distorted in the presence of resonant coupling states in the QD molecule. Single QD voltage evolution shows a crossover in the lineshape profile, which is associated to Spectral Diffusion processes due to residual charged environment.

Trabajo presentado a NanoSpain 2010 celebrado en Málaga del 23-26 Marzo, 2010. -- Incluye comunicación oral y póster., Experimental evidence of a monotonous decrease of the capillary forces between hydrophilic surfaces with increasing relative humidity from 0 to 100% is presented. In concordance with the results of a theoretical simulation, we identified the objects’ shape as the origin of different adhesion force vs. RH behaviours when treating with nanoscale objects. If the water neck is formed between a flat surface and a nanometric object presenting a truncated cone shape the adhesion force decreases with increasing vapour pressure. The variety of meniscus force behaviours found for different shapes emphasizes the importance of geometry in capillary phenomena at the nanometric scale.

[ES] El dispositivo incorpora una disposición particular de unos imanes (4) que generan un campo magnético que permite una erosión prácticamente uniforme de un cátodo o blanco (2), de modo que se consigue un aprovechamiento casi completo del material del mismo. El dispositivo magnetrón comprende, [EN] The invention relates to a device comprising a specific arrangement of magnets (4) that generate a magnetic field enabling a practically uniform erosion of a cathode or target (2), in such a way that the material thereof is almost fully used. The magnetron device comprises the target (2) fixed to a metallic plate (3) behind which magnets (4) are fixed to a magnetic plate (5). The magnets (4) are arranged according to a periodical two-dimensional network on a magnetic plate (5) that can be moved parallel to the target (2) along one of the axes of the network, between a frrst position and a second position separated by half of the parameter of the network, in such a way that areas of high plasma concentration generated in the frrst position correspond to areas of low plasma concentration in the second position and vice versa., Consejo Superior de Investigaciones Científicas (España), A2 Solicitud de patentes sin informe sobre el estado de la técnica

Dispositivo magnetrón y procedimiento de erosión uniforme de un blanco empleando dicho dispositivo. El dispositivo incorpora una disposición particular de unos imanes (4) que generan un campo magnético que permite una erosión prácticamente uniforme de un cátodo o blanco (2), de modo que se consigue un aprovechamiento casi completo del material del mismo. El dispositivo magnetrón comprende el blanco (2) fijado a una placa metálica (3) detrás de la cual se encuentran unos imanes (4) fijados a una placa magnética (5). Los imanes (4) están dispuestos según una red bidimensional periódica sobre una placa magnética (5) que se puede desplazar paralelamente al blanco (2) a lo largo de uno de los ejes de la red entre una primera posición y una segunda posición separadas la mitad del parámetro de la red, de modo que zonas de alta concentración de plasma generado en la primera posición corresponden a zonas de baja concentración de plasma en la segunda posición y viceversa., Consejo Superior de Investigaciones Científicas (España), A1 Solicitud de patentes con informe sobre el estado de la técnica

[EN] This relates to a corrosion-resistant magnetostrictive micro-mechanical element (1) for microactuators and dynamic-mode atomic force microscopy and operation compatible with corrosive media, said magnetostrictive micro-mechanical element (1) including a part (2) made of non-magnetostrictive material covered, at least on a first face, by at least one sheet (3) of magnetostrictive material that is corrosion-resistant in liquid media, such that a magnetic field parallel to the plane of the magnetostrictive sheet (3) causes the deformation of the magnetostrictive micro-mechanical element (1)., [ES] Se describe un elemento micromecánico magnetostrictivo (1) resistente a la corrosión para microactuadores y microscopía de fuerzas atómicas en modos dinámicos y funcionamiento compatible con medios corrosivos, comprendiendo dicho elemento micromecánico magnetostrictivo (1) una pieza (2) de un material no magnetostrictivo recubierta, al menos por una primera cara, por al menos (3) de material magnetostrictivo resistente a la corrosión en medios líquidos, de manera que un campo magnético paralelo al plano de la lámina (3) magnetostrictiva provoca la deformación del elemento micromecánico magnetostrictivo (1)., Consejo Superior de Investigaciones Científicas (España), A1 Solicitud de patentes con informe sobre el estado de la técnica

Elemento micromecánico magnetostrictivo resistente a la corrosión. Se describe un elemento micromecánico magnetostrictivo (1) resistente a la corrosión para microactuadores y microscopía de fuerzas atómicas en modos dinámicos y funcionamiento compatible con medios corrosivos, comprendiendo dicho elemento micromecánico magnetostrictivo (1) una pieza (2) de un material no magnetostrictivo recubierta, al menos por una primera cara, por al menos (3) de material magnetostrictivo resistente a la corrosión en medios líquidos, de manera que un campo magnético paralelo al plano de la lámina (3) magnetostrictiva provoca la deformación del elemento micromecánico magnetostrictivo (1)., Consejo Superior de Investigaciones Científicas (España), A1 Solicitud de patentes con informe sobre el estado de la técnica

2 páginas, 3 figuras.-- Comunicación oral presentada al VI Congreso Español de Fuerzas y Túnel celebrado en Segovia (España) del 22 al 25 de Septiembre del 2008., This work was financed by Spanish MEC (TEC2005-05781-C03-01, NAN2004-09109-C04-01, Consolider-Ingenio 2010 CSD2006-00019), CAM (S 0505ESP 0200) and by the SANDIE Network of excellence (Contract nº NMP4-CT-2004-500101 group TEP-0120). JMS and PAG thanks to the I3P program.

Fecha de solicitud: 21-08-2008.- Titular: Consejo Superior de Investigaciones Científicas (CSIC), The invention relates to a device for coupling light to an intermediate band solar cell (8) made from quantum dots, which also concentrates the light. The energy of the light emitting the luminescent material (2) is selected such as to produce transitions between the valence band and the conduction band of the cell. The pigments of the luminescent material (6) are selected such that the emitted photons produce transitions from the valence band to the intermediate band and from the intermediate band to the conduction band. Photonic crystals 1 and 3 prevent the light emitted by the layer (2) from escaping, while photonic crystals 4 and 5 prevent the light emitted by the material (6) from escaping. The device also includes a reflector (7) and a supporting element (9)., La invención relaciona a un dispositivo para la luz del acoplamiento a una célula solar intermedia de la banda (8) hecha de puntos del quántum, que también concentra la luz. Las energías del luminescente el material luminiscente (2) se seleccionan por ejemplo para producir transiciones entre la banda de la valencia y la banda de conducción de la célula. Los pigmentos de los 6) son del material luminiscente (seleccionaron tales que los fotones emitidos producen transiciones de la banda de la valencia a la banda intermedia y de la banda intermedia a la banda de conducción. Los cristales 1 y 3 de Photonic evitan el luz emitido por la capa (2) de escapar, cristales photonic 4 de los ratos y 5 evitan el luz emitido por el material de tipo (6) de escapar. El dispositivo también incluye un reflector (7) y un elemento de soporte (9).

Copyright American Institute of Physics 2006.-- Final full-text of the paper available at: http://dx.doi.org/10.1063/1.2399884., The origin of ferromagnetism in diluted magnetic semiconductors is still an open question, yielding a great deal of research across the world. This work focuses on the Co-Zn-O system. Room-temperature ferromagnetism is observed after a partial reaction of Co3O4 and ZnO, which can be ascribed neither to carrier mediation nor segregated cobalt metallic clusters. Another mechanism is yielding room-temperature ferromagnetism. This mechanism is associated with a partial reaction of ZnO and Co3O4 grains, and always appears when the starting phases (Co3O4 and ZnO) are present in the sample, suggesting that interfaces are involved in the origin of the observed ferromagnetism., This work has been supported by the University Complutense through the project PR1/05/13325 and CICYT project MAT2004–04843–C02–01.

The magneto-optical properties of Co microsquare— 2 μm edge—arrays have been investigated for different interelement separations, from 0.2 to 2.0 μm . The magneto-optical response is measured both at reflected and diffracted beams, and it is compared with the results of a model that uses micromagnetic simulations and optical diffraction theory to calculate the magneto-optical response for different diffracted spots. A satisfactory agreement between the experiments and the predictions from the combined micromagnetic and optical diffraction models allows the interpretation of the experimental data and provides a way to analyze and understand the physical meaning of the magneto-optic diffracted signal. The comparison of this diffracted magneto-optical experimental data with predictions from simple reversal models allows us to monitor different element magnetization reversal mechanisms as the separation between elements in the array varies., R.A.S. acknowledges support from the “Consejería de Educación de la Comunidad de Madrid.” Research funded through EC-G5RD-CT-2002–00731 HIDEMAR project.

Single phase epitaxial pure γ′-Fe4N films are grown on MgO (001) by molecular beam epitaxy of iron in the presence of nitrogen obtained from a radio frequency atomic source. The epitaxial, single phase nature of the films is revealed by x-ray diffraction and by the local magnetic environment investigated by Mössbauer spectroscopy. The macroscopic magnetic properties of the γ′-Fe4N films are studied in detail by means of transverse Kerr effect measurements. The hysteresis loops are consistent with the cubic atomic structure, displaying easy [100] magnetization directions. The films are single domain at remanence, and the reversal is dominated by 180° or 90° domain wall nucleation and propagation, depending on the applied field direction. When 90° domain walls are responsible for the magnetization reversal, this proceeds in two stages, and the measured coercive fields vary accordingly. Magnetic domain observations reveal the two distinct reversal —driven by 180° or 90° domain walls— modes displaying large domains, of the order of mm. From magnetometer techniques, the saturation magnetization, μ0Ms, is measured to be 1.8 T. A magneto-optical torque technique is used to obtain a value of the anisotropy constant of 2.9×104J/m3., The authors acknowledge partial financing from EC project HIDEMAR G5RD-CT-2002-00731 and PHANTOMS network. The authors are indebted to A. Gupta and K. V. Rao from the department of Materials Science and Engineering, KTH, Sweden for help with the low T SQUID measurements, and to L. Ballcels and M. A. García from Materials Science ICMM CSIC, Spain for high-T VSM measurements. This work was part of the research program of the Foundation for Fundamental Research on Matter-FOM, The Netherlands. J.M.G.M. acknowledges financing through the Ramón y Cajal program from the Spanish MCyT.

Multilayered TM/MgO/Fe (001) heterostructures (TM: FeCo, Co/Fe, and Fe) are grown epitaxially, to study the dependence of the magnetic coupling between the two ferromagnetic electrodes on the insulating MgO barrier width and the lateral dimensions of the structures. The crystal quality is investigated by reflection high-energy electron diffraction in situ at different growth stages of the TM/MgO/Fe(001) heterostructures. Magnetic characterization by superconducting quantum interference device magnetometry (macroscopic structures) and transverse Kerr effect (microscopic structures) shows clearly independent switching of top and bottom electrodes at large (above 20 Å) spacer thicknesses for macroscopic films. This independent switching is also observed on patterned structures. For very thin barriers, decreasing the size of the elements in patterned arrays decreases the number of junctions coupled via pinholes., The Spanish Commission of Science and Technology, and Comunidad de Madrid are acknowledged for financial support.

Comunicación oral presentada al European Materials Research Society Fall Meeting 2002, Symposium C, Fall E-MRS 2002 celebrado en Varsovia (Polonia) del 14 al 18 de Septiembre de 2002., Stress relaxation during growth of lattice-mismatched III-V semiconductor compounds can induce the formation of nanostructures. By means of an in situ and in real-time stress measurements technique, we have followed the nanostructures self-assembling process in different heteroepitaxial semiconductor systems. After explaining the basis of these in situ stress measurements, the results we have obtained on quantum dots and quantum wires formation in the systems InAs/GaAs (001), InAs/InP (001) and GaSb/GaAs (001) will be presented, together with the similarities and differences between the three systems. In the InAs/GaAs (001) system, where quantum dots are obtained, we have detected a limited In incorporation during the pseudomorphic growth of InAs on GaAs. The well known In segregation process is originated by the incorporation of this floating In during GaAs overgrowth. For InAs/InP, we have found the existence of a higher stress along [110] direction than along [1-10] when growing this system by standard molecular beam epitaxy conditions. This stress anisotropy leads to the formation of quantum wires instead of quantum dots in this system. Finally, during growth of the GaSb/GaAs (001) system quantum dots are also formed. In this case, the stress measurements show clearly the presence of mass transport coming from the wetting layer during dots formation.