Growth of (Pb,La)TiO3 and ZnO thin films on (100)InP by PulseD Laser deposition

[ES] Se ha estudiado el proceso de depósito mediante ablación con láser de láminas delgadas de PbTiO3 modificado con La (PLT) y ZnO sobre (100)InP. Para el PLT se han depositado láminas intermedias de óxidos dieléctricos (CeO2, ZrO2, SrO, YSZ, MgO, y SrTiO3) necesarias para la protección de la superficie del substrato. En cada caso se han establecido las condiciones experimentales (presión de oxígeno, temperatura del substrato, densidad de energía del pulso láser y limpieza de la superficie del substrato) necesarias para obtener láminas cristalinas con orientación preferente. En la heteroestructura PLT/YSZ/(100)InP se estudian los cambios de composición y morfología a lo largo del perfil de la heteroestructura, a fin de investigar los procesos involucrados en el crecimiento de estos óxidos sobre el (100)InP.[EN] The oriented growth of PbLaTiO3 (PLT) and ZnO thin films on (100)InP has been studied, including the influence of buffer oxide layers (CeO2, ZrO2, SrO, YSZ, MgO, and SrTiO3) on the final texture of PLT film obtained. In each case the oxygen pressure, substrate temperature, energy fluence and substrate surface conditions required to obtain a crystalline and preferentially oriented phase have been established. The composition and morphological changes related to the PLT/YSZ/(100)InP heterostructure profile have been studied in order to investigate the processes involved in the growth of these oxides on (100)InP.Este trabajo ha sido financiado por CICyT y por la Comunidad Autónoma de Madrid con de los proyectos TIC96- 1039 y 07T/0032/1997 respectivamente. E. V. está subvencionado por la Agencia Española de Cooperación Internacional a través de una beca doctoral Mutis.Peer reviewe

Aspect-ratio and lateral-resolution enhancement in force microscopy by attaching nanoclusters generated by an ion cluster source at the end of a silicon tip

One of the factors that limit the spatial resolution in atomic force microscopy (AFM) is the physical size of the probe. This limitation is particularly severe when the imaged structures are comparable in size to the tip’s apex. The resolution in the AFM is usually enhanced by using sharp tips with high aspect ratios. In the present paper we propose an approach to modify AFM tips that consists of depositing nanoclusters on standard silicon tips. We show that the use of those tips leads to atomic force microscopy images of higher aspect ratios and spatial resolution. The present approach has two major properties. It provides higher aspect-ratio images of nanoscale objects and, at the same time, enables to functionalize the AFM tips by depositing nanoparticles with well-controlled chemical composition.The authors acknowledge the Spanish Ministerio de Ciencia e Innovación and Comisión Interministerial para la Ciencia Y la Tecnología—CICYT under Contract Nos. MAT2008-06765-C02-02, MAT2009-08650, and CSD2007 00041 (Nanoselect) and through the FPI and “Juan de La Cierva” programs for financial support.Peer reviewe

Modification of AFM tips by depositing nanoparticles with an Ion Cluster Source. Enhancement of the aspect-ratio and lateral resolution

Póster presentado en la NanoSpain Conference (Nanoiberian Conference), celebrada en Bilbao del 11 al 14 de abril de 2011.One of the factors that limit the spatial resolution in atomic force microscopy (AFM) is the physical size of the probe. This limitation is particularly severe when the imaged structures are comparable in size to the tip¿s apex. The resolution in the AFM is usually enhanced by using sharp tips with high aspect ratios. In the present paper we propose an approach to modify AFM tips that consists of depositing nanoclusters on standard silicon tips. We show that the use of those tips leads to atomic force microscopy images of higher aspect ratios and spatial resolution. The present approach has two major properties. It provides higher aspect-ratio images of nanoscale objects and, at the same time, enables to functionalize the AFM tips by depositing nanoparticles with well-controlled chemical composition.Peer Reviewe

LEED-IV study of the rutile TiO2(110)-1x2 surface with a Ti-interstitial added-row reconstruction

4 pages, 2 figures, 1 table.-- PACS nrs.: 61.14.Hg; 68.35.Bs; 68.47.Gh.Upon sputtering and annealing in UHV at 1000 K the rutile TiO2(110) surface undergoes a 1x1 --> 1x2 phase transition. The resulting 1x2 surface is Ti rich, formed by strands of double Ti rows as seen on scanning tunneling microscopic images, but its detailed structure and composition have been subject to debate in the literature for years. Recently, Park et al. [Phys. Rev. Lett. 96 226105 (2006)] have proposed a model where Ti atoms are located on interstitial sites with Ti2O stoichiometry. This model, when it is analyzed using LEED-IV data [Phys. Rev. Lett. 96 0055502 (2006)] does not yield an agreement between theory and experiment as good as the previous best fit for Onishi and Iwasawa's model for the long-range 1x2 reconstruction. Therefore, the Ti2O3 added row is the preferred one from the point of view of low-energy electron diffraction.This work has been financed by the CYCIT (Grant No. MAT-2005-3866). M.B.R. acknowledges Spanish CSIC for financial support through I3P program. The Barcelona Supercomputer Center (http://www.bsc.es/) is acknowledged for computing time.Peer reviewe

Time-Resolved Characterization of Dynamic Tribochemical Processes for Dicationic Imidazolium Ionic Liquid

Dynamic tribochemical processes for dicationic ionic liquid containing a geminal imidazolium cation head group bridged by a poly(ethylene glycol) and a bis(trifluoromethylsulfonyl)imide anion were studied using time-resolved mechanically stimulated gas emission mass-spectrometry (MSGE-MS). In comparison with similar monocationic imidazolium ionic liquids with short alkyl or long polyether side chains, the dicationic ionic liquid had a lower coefficient of friction on Ti6Al4V alloy and smoother behavior. The analysis of volatile decomposition products suggested multiple tribochemical reactions in which both anionic and cationic moieties are involved. The tribochemical degradation of cations was mainly through the detachment of the side and bridging chains from the imidazolium head groups. The absence of volatile products containing nitrogen implies that the imidazole group remained unchanged. Hydrogen and water desorption were attributed to the reactions of hydrogen fluoride being a product of anion degradation with titanium and titanium oxide, respectively.: The authors are grateful to M. Mahrova for providing the synthesized IL. The authors acknowledge the help of O. Sanchez in measuring the surface profiles. This work was supported by the Ministry of Economy and Competitiveness of Spain through the grant BIA2016-79528-R.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

C60 fullereno modified by low-energy ion beams to prevent the multipactor effect

[ES] Se ha estudiado la interacción de los iones H2+, N2+, O2+ y Ar+ de baja energía con películas delgadas de fullereno C60. Después del bombardeo iónico, la densidad de estados cerca del nivel de Fermi aumenta de forma apreciable, según se observa en los espectros de fotoemisión obtenidos usando radiación sincrotrón. El bombardeo iónico con una energía de tan sólo 50 eV y una fluencia de 4x10^14 ion/cm2 es suficiente para modificar la simétrica estructura de caja del fullereno y obtener carbono amorfo grafítico. El nitrógeno y el oxígeno se implantan al bombardear con una energía de 50 eV, mientras que la implantación es despreciable en el caso del hidrógeno y argon. Las películas de fullereno poseen un coeficiente máximo de emisión secundaria inferior a 1.3 incluso después de su exposición al aire, el cual disminuye después del bombardeo con iones de N2+ y Ar+.[EN] C60 fullerene modified by low-energy ion beams of H2+, N2+, O2+ and Ar+ has been studied. After ion bombardment, the photoemission spectra obtained using synchrotron radiation show an increase of the density of states just bellow the Fermi level. Ion bombarment of C60 with 50 eV energy and 4×1014 ion/cm2 fluence is sufficient to modify the cage structure of the fullerene and to obtain graphitic amorphous carbon. Upon bombarding with an energy of 50 eV, implantation of the nitrogen and the oxygen ions was observed, while implantation of the hydrogen and argon ions was small. The maximum secondary emission yield of C60 thin films is lower than 1.3 even after air exposure. A significant improvement on the secondary emission properties can be obtained after bombardment by low-energy Ar+ and N2+ ion beams.Financiación del Ministerio de Ciencia y Tecnología de España, proyecto coordinado n: ESP2002-04509-C04-04 y ESP2002-04509-C04-02, y de la Comunidad Europea proyecto TMR n: ERBFMGECT950022.Peer reviewe

Dispositivo y método para limpiar superficies con haz de gases en vacío y ultra alto vacío

[EN] The present invention relates to a device and a method for cleaning surfaces using a beam consisting of gases under vacuum or ultra high vacuum. Both the device and method involve bombarding with molecules, not ionized particles. The device comprises: a differential pump system (5) and a chamber (6) which comprises: an inlet (7) for the injection of a non-ionized gas (11); a molecule aggregation zone (8); a nozzle (9) with an outlet (10) that can be connected to the differential pump system and to the vacuum or ultra high vacuum system (2); wherein the gas molecules enter the aggregation zone where they are accelerated by the differential pump system, so that the molecules collide, forming a beam (12) of aggregated molecules that pass through the outlet of the nozzle before striking the surface (3) of the object (4) to be cleaned[ES] La presente invención propone un dispositivo y un método para limpiar superficies con haz de gases en vacío y ultra alto vacío. Ambos, dispositivo y método, se basan en bombardeo de moléculas y no de partículas ionizadas. El dispositivo comprende: un sistema de bombeo diferencial (5) y una cámara (6) que comprende: una entrada (7) para la inyección de un gas no ionizado (11); una zona de agregación (8) de moléculas; un embudo (9) que comprende una salida (10) conectable con el sistema de bombeo diferencial y con el sistema de vacío o ultra alto vacío (2); tal que las moléculas del gas entran en la zona de agregación donde son aceleradas por el sistema de bombeo diferencial, de forma que las moléculas chocan entre sí formando un haz de agregados moleculares (12) que atraviesan la salida del embudo hasta chocar con la superficie (3) del objeto a limpiar (4)Peer reviewedConsejo Superior de Investigaciones CientíficasA1 Solicitud de patente con informe sobre el estado de la técnic

Procedimiento y dispositivo para determinar el contenido de gases y volátiles en materiales sólidos o recubrimientos de superficie

Procedimiento y dispositivo para determinar el contenido de gases y volátiles en materiales sólidos o recubrimientos de superficie. La presente invención describe un procedimiento y un dispositivo para determinar la cantidad de gases y volátiles contenido en materiales sólidos y en recubrimientos de superficies, por ejemplo hidrógeno, utilizando un dispositivo mecánico en vacío. El procedimiento consiste en medir la cantidad de gases liberados en una cámara de vacío mediante una acción mecánica como el deslizamiento, rodadura o indentación, preferentemente con un buril o punzón sobre la superficie del material. Este procedimiento se puede utilizar como control de calidad de materiales sólidos tales como metales, aleaciones metálicas, cerámicas, elastómeros y plásticos, que son utilizados en industrias de transporte de petróleo o gas natural, siderurgia, en transporte férreo, industria química, sector aeroespacial, energía nuclear, así como en las grandes instalaciones de haces de partículas.Consejo Superior de Investigaciones Científicas (España)B1 Patente con informe sobre el estado de la ténic

Procedimiento y dispositivo para determinar el contenido de gases y volátiles en materiales sólidos o recubrimientos de superficie

Fecha de solicitud: 28-08-2008.- Titular: Consejo Superior de Investigaciones Científicas (CSIC)The present invention describes a method and device for determining the amount of gases and volatile agents contained in solid materials and surface coverings, for example hydrogen, using a mechanical device in a vacuum. The method comprises measuring the quantity of gases released in a vacuum chamber by means of a mechanical actions such as sliding, rolling or denting, preferably with a chisel or punch on the material surface. This method can be used for quality control of solid materials such as metals, metal alloys, ceramics, elastomers and plastics, which are used in the petroleum or natural gas transport industries, steelmaking, in rail transport, chemical industries, aerospace, nuclear energy, and in major particle beam installations.La presente invención describe un método y dispositivo para la determinación de la cantidad de los gases y de los agentes volátiles contenidos en materiales sólidos y recubrimientos de la superficie, por ejemplo hidrógenos, usando un dispositivo mecánico en un vacío. El método comprende medir la cantidad de gas liberada en cámaras de vacío por medio de las acciones mecánicas tales como resbalar, laminación o abollar, preferiblemente con un cincel o un punzón en la superficie de material. Este bote del método sea utilizado para el control de calidad de materiales sólidos tales como metales, aleaciones metálicas, cerámica, elastómeros y plásticos, que son utilizado en las industrias del transporte de los petróleos o del gas natural, siderurgia, en el transporte del carril, industrias del producto químico, espacio aéreo, energías nucleares, y en instalaciones principales de la haz de la partícula.Peer reviewe

Origin of hydrogen desorption during friction of stainless steel by alumina in ultrahigh vacuum

6 pages.A study of the tribodesorption of hydrogen stimulated by the friction of an alumina pin on stainless steel in ultrahigh vacuum at room temperature is presented. A special two-chamber ultrahigh-vacuum system separated by a well-defined orifice of low conductance is used to determine minute amounts of desorbed gases. The friction cell allows the control of the normal force of the alumina pin on the stainless-steel surface, the frequency of sweeping, as well as the dwell, i.e., the time between consecutive strokes. The profile of the p(H2)-t desorption curve shows a near-exponential increase in pressure to a stable value; then, after the friction cessation, the pressure decreases back to the initial value. The desorption curve presents an oscillating signal over the continuous one that corresponds with the sweeping frequency. An important aspect of the present research has been to elucidate the origin of the desorbed hydrogen: bulk or surface of materials. In this respect, the amount of tribodesorbed hydrogen is compared with the amount of adsorbed hydrogen at dwell times from 0.5 to 4 s. This adsorption is 50 and 5 times lower than the desorbed hydrogen at normal forces of 0.072 and 0.218 N, respectively, and a dwell time of 4 s. An important finding is that the amount of desorbed hydrogen is irrespective of the dwell time, and the desorption rate increases linearly with sweeping frequency. The authors conclude that the origin of the desorbed hydrogen is in the bulk.Peer reviewe