Nanomaterials Growth Unit

Unit Leader: José Santiso

Publications

2020

  • Revealing Strain Effects on the Chemical Composition of Perovskite Oxide Thin Films Surface, Bulk, and Interfaces

    van den Bosch C.A.M., Cavallaro A., Moreno R., Cibin G., Kerherve G., Caicedo J.M., Lippert T.K., Doebeli M., Santiso J., Skinner S.J., Aguadero A. Advanced Materials Interfaces; 7 (2, 1901440) 2020. 10.1002/admi.201901440. IF: 4.713

    Understanding the effects of lattice strain on oxygen surface and diffusion kinetics in oxides is a controversial subject that is critical for developing efficient energy storage and conversion materials. In this work, high-quality epitaxial thin films of the model perovskite La0.5Sr0.5Mn0.5Co0.5O3− δ (LSMC), under compressive or tensile strain, are characterized with a combination of in situ and ex situ bulk and surface-sensitive techniques. The results demonstrate a nonlinear correlation of mechanical and chemical properties as a function of the operation conditions. It is observed that the effect of strain on reducibility is dependent on the “effective strain” induced on the chemical bonds. In-plain strain, and in particular the relative BO length bond, is the key factor controlling which of the B-site cation can be reduced preferentially. Furthermore, the need to use a set of complimentary techniques to isolate different chemically induced strain effects is proven. With this, it is confirmed that tensile strain favors the stabilization of a more reduced lattice, accompanied by greater segregation of strontium secondary phases and a decrease of oxygen exchange kinetics on LSMC thin films. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • The formation of oriented barium carbonate from the decomposition of yttria-doped barium zirconate films

    Jennings D., Ricote S., Santiso J., Reimanis I. Scripta Materialia; 186: 401 - 405. 2020. 10.1016/j.scriptamat.2020.05.028. IF: 4.539

    Yttria doped barium zirconate (BZY) thin films show promise thanks to their high proton conductivities and their possibility for use in studying fundamental processes such as exsolution. This work demonstrates that highly oriented BZY thin (45 nm) films on (100) single crystal strontium titanate decompose into oriented barium carbonate rods and yttria stabilized zirconia when exposed to industrial grade Ar or pure CO2 at 800 °C. It is shown with transmission electron microscopy that the rods nucleate on the BZY surface. The causes and modes of decomposition in these thin films are discussed in detail. © 2020 Acta Materialia Inc.


2019

  • Bipolar “table with legs” resistive switching in epitaxial perovskite heterostructures

    Bagdzevicius S., Boudard M., Caicedo J.M., Mescot X., Rodríguez-Lamas R., Santiso J., Burriel M. Solid State Ionics; 334: 29 - 35. 2019. 10.1016/j.ssi.2019.01.027. IF: 2.886

    We report the experimental investigation of bipolar resistive switching with “table with legs” shaped hysteresis switching loops in epitaxial perovskite GdBaCo 2 O 5+δ /LaNiO 3 bilayers deposited by pulsed laser deposition. The possibility of varying the resistivity of GdBaCo 2 O 5+δ by changing its oxygen content allowed engineering this perovskite heterostructure with controlled interfaces creating two symmetric junctions. It has been proved that the resistance state of the device can be reproducibly varied by both continuous voltage sweeps and by electrical pulses. The symmetric devices show slightly non-symmetric resistance profiles, which can be explained by a valence change resistive switching model, and presented promising multilevel properties required for novel memories and neuromorphic computing. © 2019


  • Enhanced thermoelectric properties of lightly Nb doped SrTiO3 thin films

    Bhansali S., Khunsin W., Chatterjee A., Santiso J., Abad B., Martin-Gonzalez M., Jakob G., Sotomayor Torres C.M., Chávez-Angel E. Nanoscale Advances; 1 (9): 3647 - 3653. 2019. 10.1039/c9na00361d. IF: 0.000

    Novel thermoelectric materials developed for operation at room temperature must have similar or better performance along with being as ecofriendly as those commercially used, e.g., Bi2Te3, in terms of their toxicity and cost. In this work, we present an in-depth study of the thermoelectric properties of epitaxial Nb-doped strontium titanate (SrTi1-xNbxO3) thin films as a function of (i) doping concentration, (ii) film thickness and (iii) substrate type. The excellent crystal quality was confirmed by high resolution transmission electron microscopy and X-ray diffraction analysis. The thermoelectric properties were measured by the three-omega method (thermal conductivity) and van der Pauw method (electrical resistivity), complemented by Seebeck coefficient measurements. A maximum power factor of 8.9 × 10-3 W m-1 K-2 and a thermoelectric figure of merit of 0.49 were measured at room temperature in 50 nm-thick films grown on lanthanum strontium aluminate. The mechanisms behind this high figure of merit are discussed in terms of a possible two-dimensional electron gas, increase of the effective mass of the electrons, electron filtering and change in strain due to different substrates. The overall enhancement of the thermoelectric properties suggests that SrTi1-xNbxO3 is a very promising n-type candidate for room- to high-temperature applications. © 2019 The Royal Society of Chemistry.


  • Independent Tuning of Optical Transparency Window and Electrical Properties of Epitaxial SrVO3 Thin Films by Substrate Mismatch

    Mirjolet M., Vasili H.B., López-Conesa L., Estradé S., Peiró F., Santiso J., Sánchez F., Machado P., Gargiani P., Valvidares M., Fontcuberta J. Advanced Functional Materials; 29 (37, 1904238) 2019. 10.1002/adfm.201904238. IF: 15.621

    Transparent metallic oxides are pivotal materials in information technology, photovoltaics, or even in architecture. They display the rare combination of metallicity and transparency in the visible range because of weak interband photon absorption and weak screening of free carriers to impinging light. However, the workhorse of current technology, indium tin oxide (ITO), is facing severe limitations and alternative approaches are needed. AMO3 perovskites, M being a nd1 transition metal, and A an alkaline earth, have a genuine metallic character and, in contrast to conventional metals, the electron–electron correlations within the nd1 band enhance the carriers effective mass (m*) and bring the transparency window limit (marked by the plasma frequency, ωp*) down to the infrared. Here, it is shown that epitaxial strain and carrier concentration allow fine tuning of optical properties (ωp*) of SrVO3 films by modulating m* due to strain-induced selective symmetry breaking of 3d-t2g(xy, yz, xz) orbitals. Interestingly, the DC electrical properties can be varied by a large extent depending on growth conditions whereas the optical transparency window in the visible is basically preserved. These observations suggest that the harsh conditions required to grow optimal SrVO3 films may not be a bottleneck for their future application. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • Nanostructural changes upon substitutional Al doping in ZnO sputtered films

    Landa-Cánovas A.R., Santiso J., Agulló-Rueda F., Herrero P., Navarrete-Astorga E., Ochoa-Martínez E., Ramos-Barrado J.R., Gabás M. Ceramics International; 45 (5): 6319 - 6327. 2019. 10.1016/j.ceramint.2018.12.116. IF: 3.450

    Al:ZnO layers, with low and high Al content, 0.2% and 2.1% cat. respectively, have been prepared using the RF magnetron sputtering technique. Noticeable differences in the optical and electrical properties have been detected in these films. With doping, the resistivity decreases and the band-gap increases. The alterations in the films crystalline structure are explained in terms of the nanostructural changes induced by Al substitutional doping, such as a higher concentration of edge dislocation defects and a higher rotation of crystalline nanodomains in the plane of the films (normal to the preferential orientation c-axis) for the high content Al:ZnO layer. A complete description of such effects has been accomplished using several characterization techniques, such as X-ray diffraction, Raman spectroscopy and transmission electron microscopy. The combination of these techniques provides an exhaustive understanding of the films nanostructure. © 2018 Elsevier Ltd and Techna Group S.r.l.


  • Puzzling robust 2D metallic conductivity in undoped β-Ga 2 O 3 thin films

    Chikoidze E., Rogers D.J., Teherani F.H., Rubio C., Sauthier G., Von Bardeleben H.J., Tchelidze T., Ton-That C., Fellous A., Bove P., Sandana E.V., Dumont Y., Perez-Tomas A. Materials Today Physics; 8: 10 - 17. 2019. 10.1016/j.mtphys.2018.11.006. IF: 0.000

    Here, we report the analogy of an extremely stable topological-like ultra-wide bandgap insulator, a solid that is a pure insulator in its bulk but has a metallic conductive surface, presenting a two-dimensional conductive channel at its surface that challenges our current thinking about semiconductor conductivity engineering. Nominally undoped epitaxial β-Ga 2 O 3 thin films without any detectable defect (after a range of state-of-the-art techniques) showed the unexpectedly low resistivity of 3 × 10 −2 Ωcm which was found to be also resistant to high dose proton irradiation (2 MeV, 5 × 10 15 cm −2 dose) and was largely invariant (metallic) over the phenomenal temperature range of 2 K up to 850 K. The unique resilience and stability of the electrical properties under thermal and highly ionizing radiation stressing, combined with the extended transparency range (thanks to the ultra-wide bandgap) and the already known toughness under high electrical field could open up new perspectives for use as expanded spectral range transparent electrodes (e.g., for UV harvesting solar cells or UV LEDs/lasers) and robust Ohmic contacts for use in extreme environments/applications and for novel optoelectronic and power device concepts. © 2018 Elsevier Ltd


  • Superposition of interface and volume type resistive switching in perovskite nanoionic devices

    Bagdzevicius S., Boudard M., Caicedo J.M., Rapenne L., Mescot X., Rodríguez-Lamas R., Robaut F., Santiso J., Burriel M. Journal of Materials Chemistry C; 7 (25): 7580 - 7592. 2019. 10.1039/c9tc00609e. IF: 6.641

    The microelectronics industry is currently searching for reliable redox-based resistive switching (RS) memories which are filament-free, scale with the electrode size and do not require a high voltage electroforming step. Interface and volume type switching devices are the most promising memristors to achieve these challenging requirements, both for ReRAM (Resistive Random-Access Memories) non-volatile memory and neuromorphic computing applications. Here RS was investigated for the first time in nanoionic memristors based on GdBaCo2O5+δ (GBCO), an oxide with high oxygen mobility. Non-filamentary and non-volatile reproducible RS was obtained when GBCO is sandwiched between Ag and LaNiO3 (LNO) electrodes. The observed bipolar RS could be successfully induced both by voltage sweeps and by pulses, showing asymmetric clock-wise hysteretic R(V) characteristics at room temperature. The temperature dependence of two independent devices in high and low resistance states (HRS and LRS) revealed a gradual decrease of the resistance difference between the two states on cooling from room temperature to 150 K and its increase below 100 K. Similarly, the R(V) switching curves obtained at low temperature showed the disappearance of the hysteresis at 150 K and its reappearance at lower temperatures. The superposition of volume and interface type RS mechanisms have proven to be responsible for the observed non-volatile change of the remnant resistance. The volume-type RS was related to the variation of the GBCO resistivity due to a change in oxygen content. The interface-type RS, on the other hand, was associated to the created electronic and ionic conduction barrier between GBCO and the LNO bottom electrode. © 2019 The Royal Society of Chemistry.


  • Thin film oxide-ion conducting electrolyte for near room temperature applications

    Garbayo I., Chiabrera F., Alayo N., Santiso J., Morata A., Tarancón A. Journal of Materials Chemistry A; 7 (45): 25772 - 25778. 2019. 10.1039/c9ta07632h. IF: 10.733

    Stabilized bismuth vanadate thin films are presented here as superior oxide ionic conductors, for application in solid state electrochemical devices operating near room temperature. Widely studied in the 90s in bulk form due to their unbeatable ionic conduction, this family of materials was finally discarded due to poor stability above 500 °C. Here, we however unveil the possibility of using Bi4V1.8Cu0.2O10.7 at reduced temperatures in thin film-based devices, where the material keeps its unmatched conduction properties and at the same time shows good stability over a wide oxygen partial pressure range. © 2019 The Royal Society of Chemistry.


2018

  • An in operando study of chemical expansion and oxygen surface exchange rates in epitaxial GdBaCo2O5.5 electrodes in a solid-state electrochemical cell by time-resolved X-ray diffraction

    Chatterjee A., Caicedo J.M., Ballesteros B., Santiso J. Journal of Materials Chemistry A; 6 (26): 12430 - 12439. 2018. 10.1039/c8ta02790k. IF: 9.931

    This report explores the fundamental characteristics of epitaxial thin films of a mixed ionic electronic conducting GdBaCo2O5.5±δ (GBCO) material with a layered perovskite structure, relevant for use as an active electrode for the oxygen reduction and evolution reactions in electrochemical devices. Time-resolved X-ray diffraction in combination with voltage step chrono-amperometric measurements in a solid state electrochemical cell provides a deeper insight into the chemical expansion mechanism in the GBCO electrode. The chemical expansion coefficient along the c-axis, αc, shows a negative value upon the compound oxidation contrary to standard perovskite materials with disordered oxygen vacancies. Chemical expansion also shows a remarkable asymmetry from αc = -0.037 to -0.014 at δ < 0 and δ > 0, respectively. This change in chemical expansion is an indication of a different mechanism of the structural changes associated with the variable Co cation oxidation state from Co2+ → Co3+ → Co4+. Since redox reactions are dominated by oxygen surface exchange between the GBCO electrode and gas atmosphere, monitoring the time response of the structural changes allows for direct determination of oxygen reduction and evolution reaction kinetics. The reaction kinetics are progressively slowed down upon reduction in the δ < 0 oxygen stoichiometry region, while they maintain a high catalytic activity in the δ > 0 region, in agreement with the structural changes and the electronic carrier delocalization when crossing δ = 0. This work validates the time-resolved XRD technique for fast and reversible measurements of electrode activity in a wide range of oxygen non-stoichiometry in a solid-state electrochemical cell operating under realistic working conditions. © 2018 The Royal Society of Chemistry.


  • Atomic resolution imaging and quantitative elemental mapping of the misfit dislocation core phase in multicomponent oxides

    Bagués N., Santiso J., Esser B.D., Williams R.E.A., McComb D.W., Konstantinovic Z., Balcells Ll., Sandiumenge F. Microscopy and Microanalysis; 24 (S1): 24 - 25. 2018. 10.1017/S1431927618000612. IF: 2.124

    The relaxation mechanisms of lattice mismatched heteroepitaxial films may accommodate defects, such as misfit dislocations (MDs). Such MDs are located at the interface between two different compounds and can be considered linear defects exhibiting their own distinct structural, chemical, and physical properties. Recent studies have highlighted the strong potential of buried and laterally ordered MD networks in creating a variety of periodic strain-induced functional patterns in oxide thin films [1–3]. These recent findings have motivated analysis of the atomic and chemical structure of the MD phase in complex oxides,in view of the development of functional dislocation-based nanostructures. In this work, we combine imaging and spectroscopic techniques to determine the complex structure of MDs in the perovskite type La0.67Sr0.33MnO3/LaAlO3 (LSMO/LAO) heteroepitaxial system. The atomic structure of the core and surrounding area of the MDs is analyzed by high resolution (HR) transmission electron microscopy (TEM) and aberration-corrected scanning (S)TEM, as well as its chemical and electronic configuration by means of energy dispersive x-ray (EDS) spectral mapping and electron energy-loss (EELS) spectrum images. A high angle annular dark field (HAADF) STEM image of a MD core at the LSMO-LAO interface is shown in Figure 1. This MD is characterized by a a[010] Burgers vector parallel to the LSMO-LAO interface, where a is the LAO lattice parameter. A careful analysis of the HR-TEM and HR-HAADF data reveals that the dislocation core is dissociated and presents two extra half-planes separated by one unit cell. The strain field associated with this dislocation is characterized by tensile and compressive regions extending above and below the dislocation glide plane, which is parallel to LSMO-LAOinterface. The HAADF images of the MD core indicate the formation of a La୑୬୶ anti-site defect in the tensile zone to accommodate the tensile strain. The atomic resolution EDS and EELS analyses reveal that, while the position of the LSMO-LAO interface is blurred by cation intermixing, oxygen vacancies selectively accumulate in the tensile region of the dislocation strain field. Such accumulation of vacancies is accompanied by the reduction of Mn cations in the same area. The imbalance between the concentration of oxygen vacancies and the rate of Sr diffusion out of the core results in a positive net charge q ≈ +0.3 ± 0.1 localized in the tensile region of the dislocation, while the compressive region remains neutral. The basic mechanisms involve in the distribution of cations and oxygen vacancies around the MD core are schematically summarized in the right panel of Figure 1. These results highlight a prototypical core model for perovskite-based heteroepitaxial systems and offer insights into predictive manipulation of MD properties [4, 5].


  • Growth and structural characterization of strained epitaxial H f0.5 Z r0.5 O2 thin films

    Torrejón L., Langenberg E., Magén C., Larrea Á., Blasco J., Santiso J., Algarabel P.A., Pardo J.A. Physical Review Materials; 2 (1, 013401) 2018. 10.1103/PhysRevMaterials.2.013401.

    Ferroelectricity was recently reported in thin films with several compositions in the HfO2-ZrO2 system with orthorhombic crystal structure. In the present paper we study the growth by pulsed laser deposition and the structural characterization of strained epitaxial Hf0.5Zr0.5O2 films on (001)-oriented yttria-stabilized zirconia (YSZ) substrates. We have determined the conditions for the coherent growth and correlated the deposition parameters with the films structure and microstructure studied through a combination of x-ray diffraction, electron backscatter diffraction, and scanning transmission electron microscopy. In the range of experimental parameters explored, all the films show monoclinic structure with distorted lattice parameters relative to bulk. © 2018 American Physical Society.


  • Optimisation of growth parameters to obtain epitaxial Y-doped BaZrO3 proton conducting thin films

    Magrasó A., Ballesteros B., Rodríguez-Lamas R., Sunding M.F., Santiso J. Solid State Ionics; 314: 9 - 16. 2018. 10.1016/j.ssi.2017.11.002. IF: 2.751

    We hereby report developments on the fabrication and characterization of epitaxial thin films of proton conducting Y-doped BaZrO3 (BZY) by pulsed laser deposition (PLD) on different single crystal substrates (MgO, GdScO3, SrTiO3, NdGaO3, LaAlO3 and sapphire) using Ni-free and 1% Ni-containing targets. Pure, high crystal quality epitaxial films of BZY are obtained on MgO and on perovskite-type substrates, despite the large lattice mismatch. The deposition conditions influence the morphology, cell parameters and chemical composition of the film, the oxygen partial pressure during film growth being the most determining. Film characterization was carried out using X-ray diffraction, transmission electron and atomic force microscopies, wavelength dispersive X-ray spectroscopy and angle-resolved X-ray photoelectron spectroscopy. All films show a slight tetragonal distortion that is not directly related to the substrate-induced strain. The proton conductivity of the films depends on deposition conditions and film thickness, and for the optimised conditions its total conductivity is slightly higher than the bulk conductivity of the target material (3 mS/cm at 600 °C, in wet 5% H2/Ar). The conductivities are, however, more than one order of magnitude lower than the highest reported in literature and possible reasoning is elucidated in terms of local and extended defects in the films. © 2017 Elsevier B.V.


  • Substrate Dependence of the Freezing Dynamics of Supercooled Water Films: A High-Speed Optical Microscope Study

    Pach E., Rodriguez L., Verdaguer A. Journal of Physical Chemistry B; 122 (2): 818 - 826. 2018. 10.1021/acs.jpcb.7b06933. IF: 3.146

    The freezing of supercooled water films on different substrates was investigated using a high-speed camera coupled to an optical microscope, obtaining details of the freezing process not described in the literature before. We observed the two well known freezing stages (fast dendritic growth and slow freezing of the water liquid left after the dendritic growth), but we separated the process into different phenomena that were studied separately: two-dimensional dendrite growth on the substrate interface, vertical dendrite growth, formation and evolution of ice domains, trapping of air bubbles and freezing of the water film surface. We found all of these processes to be dependent on both the supercooling temperature and the substrate used. Ice dendrite (or ice front) growth during the first stage was found to be dependent on thermal properties of the substrate but could not be unequivocally related to them. Finally, for low supercooling, a direct relationship was observed between the morphology of the dendrites formed in the first stage, which depends on the substrate, and the roughness and the shape of the surface of the ice, when freezing of the film was completed. This opens the possibility of using surfaces and coatings to control ice morphology beyond anti-icing properties. © 2017 American Chemical Society.


  • The Misfit Dislocation Core Phase in Complex Oxide Heteroepitaxy

    Bagués N., Santiso J., Esser B.D., Williams R.E.A., McComb D.W., Konstantinovic Z., Balcells L., Sandiumenge F. Advanced Functional Materials; 28 (8, 1704437) 2018. 10.1002/adfm.201704437. IF: 13.325

    Misfit dislocations form self-organized nanoscale linear defects exhibiting their own distinct structural, chemical, and physical properties which, particularly in complex oxides, hold a strong potential for the development of nanodevices. However, the transformation of such defects from passive into potentially active functional elements necessitates a deep understanding of the particular mechanisms governing their formation. Here, different atomic resolution imaging and spectroscopic techniques are combined to determine the complex structure of misfit dislocations in the perovskite type La0.67Sr0.33MnO3/LaAlO3 heteroepitaxial system. It is found that while the position of the film–substrate interface is blurred by cation intermixing, oxygen vacancies selectively accumulate at the tensile region of the dislocation strain field. Such accumulation of vacancies is accompanied by the reduction of manganese cations in the same area, inducing chemical expansion effects, which partly accommodate the dislocation strain. The formation of oxygen vacancies is only partially electrically compensated and results in a positive net charge q ≈ +0.3 ± 0.1 localized in the tensile region of the dislocation, while the compressive region remains neutral. The results highlight a prototypical core model for perovskite-based heteroepitaxial systems and offer insights for predictive manipulation of misfit dislocation properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


2017

  • Domain wall magnetoresistance in BiFeO3 thin films measured by scanning probe microscopy

    Domingo N., Farokhipoor S., Santiso J., Noheda B., Catalan G. Journal of Physics Condensed Matter; 29 (33, 334003) 2017. 10.1088/1361-648X/aa7a24. IF: 2.678

    We measure the magnetotransport properties of individual 71° domain walls in multiferroic BiFeO3 by means of conductive-atomic force microscopy (C-AFM) in the presence of magnetic fields up to one Tesla. The results suggest anisotropic magnetoresistance at room temperature, with the sign of the magnetoresistance depending on the relative orientation between the magnetic field and the domain wall plane. A consequence of this finding is that macroscopically averaged magnetoresistance measurements for domain wall bunches are likely to underestimate the magnetoresistance of each individual domain wall. © 2017 IOP Publishing Ltd.


  • On the persistence of polar domains in ultrathin ferroelectric capacitors

    Zubko P., Lu H., Bark C.-W., Martí X., Santiso J., Eom C.-B., Catalan G., Gruverman A. Journal of Physics Condensed Matter; 29 (28, 284001) 2017. 10.1088/1361-648X/aa73c3. IF: 2.678

    The instability of ferroelectric ordering in ultra-thin films is one of the most important fundamental issues pertaining realization of a number of electronic devices with enhanced functionality, such as ferroelectric and multiferroic tunnel junctions or ferroelectric field effect transistors. In this paper, we investigate the polarization state of archetypal ultrathin (several nanometres) ferroelectric heterostructures: epitaxial single-crystalline BaTiO3 films sandwiched between the most habitual perovskite electrodes, SrRuO3, on top of the most used perovskite substrate, SrTiO3. We use a combination of piezoresponse force microscopy, dielectric measurements and structural characterization to provide conclusive evidence for the ferroelectric nature of the relaxed polarization state in ultrathin BaTiO3 capacitors. We show that even the high screening efficiency of SrRuO3 electrodes is still insufficient to stabilize polarization in SrRuO3/BaTiO3/SrRuO3 heterostructures at room temperature. We identify the key role of domain wall motion in determining the macroscopic electrical properties of ultrathin capacitors and discuss their dielectric response in the light of the recent interest in negative capacitance behaviour. © 2017 IOP Publishing Ltd.


2016

  • Comparison of the local and the average crystal structure of proton conducting lanthanum tungstate and the influence of molybdenum substitution

    Magrasó A., Frontera C. Dalton Transactions; 45 (9): 3791 - 3797. 2016. 10.1039/c5dt04659a. IF: 4.177

    We report on the comparison of the local and average structure reported recently for proton conducting lanthanum tungstate, of general formula La28-xW4+xO54+δv2-δ, and the impact of molybdenum-substitution on the crystal structure of the material. Partial replacement of W with 10 and 30 mol% Mo is investigated here, i.e. La27(W1-xMox)5O55.5 for x = 0.1 and 0.3. This study addresses the interpretation and the description of a disordered cation and anion sublattice in this material, which enables the understanding of the fundamental properties related to hydration, transport properties and degradation in lanthanum tungstate. The report shows that Mo-substituted lanthanum tungstate is a promising material as a dense oxide membrane for hydrogen separation at intermediate temperatures. © The Royal Society of Chemistry 2016.


  • Effect of tri- and tetravalent metal doping on the electrochemical properties of lanthanum tungstate proton conductors

    Porras-Vázquez J.M., Dos Santos-Gómez L., Marrero-López D., Slater P.R., Masó N., Magrasó A., Losilla E.R. Dalton Transactions; 45 (7): 3130 - 3138. 2016. 10.1039/c5dt03833b. IF: 4.177

    Rare-earth tungstates (La28-yW4+yO54+δ□2-δ) have attracted attention recently because of their relatively high proton-electron conductivity and high stability in a CO2 environment. Since doping on the tungsten-site may increase the conductivity, a new series of compounds with composition La5.5W1-xMxO11.25-δ (M = Al, Ti and Zr; x = 0, 0.05 and 0.10) have been investigated. The crystal structure of these materials has been studied using X-ray and time-of-flight neutron powder diffraction by Rietveld analysis. The concentration of oxygen vacancies for hydration in the structure has been indirectly determined by thermogravimetric analysis, and the total conductivity in several pO2, pH2O and pD2O atmospheres has been studied by impedance spectroscopy. An increase in the conductivity is observed, ranging from 4.1 mS cm-1 for the undoped sample to 9.2 mS cm-1 for La5.5W0.9Ti0.1O11.25-δ, in wet N2 at 800°C. © The Royal Society of Chemistry 2016.


  • Fabrication of phononic crystals on free-standing silicon membranes

    Sledzinska M., Graczykowski B., Alzina F., Santiso Lopez J., Sotomayor Torres C.M. Microelectronic Engineering; 149: 41 - 45. 2016. 10.1016/j.mee.2015.09.004. IF: 1.277

    Free-standing Si films have been and remain an excellent example to study experimentally the effect of the reduction of the characteristic size on the phonon dispersion relation. A step further in geometrical complexity and, therefore, in increasing the control and manipulation of phonons is achieved by introducing periodicity in the medium to form phononic crystals. Here we report on the development of the fabrication process of large-area, solid-air and solid-solid two-dimensional phononic crystals, directly on free-standing, single crystalline silicon membranes. The patterning of the membranes involved electron-beam lithography and reactive ion etching for holes or metal evaporation and lift-off for pillars. The fabrication was possible due to the external strain induced on the membrane in order to reduce the buckling, which is typically found in large area free-standing structures. As a result, we obtained 250 nm thick structured membranes with patterned areas up to 100 × 100 μm, feature size between 100 and 300 nm and periodicity between 300 and 500 nm. The changes in dispersion relations of hypersonic acoustic phonons due to nanopatterning in free-standing silicon membranes were measured by Brillouin light scattering and the results were compared with numerical calculations by finite elements method. Information on phonon dispersion relation combined with a reliable fabrication process for large-scale structures opens a way for phonon engineering in more complex devices. © 2015 Elsevier B.V. All rights reserved.


  • Formation of self-organized Mn3O4 nanoinclusions in LaMnO3 films

    A. Pomar, Z. Konstantinović, N. Bagués, J. Roqueta, L. López-Mir, Ll. Balcells, C. Frontera, N. Mestres, A. Gutiérrez-Llorente, M. Šćepanović, N. Lazarević, Z. V Popović, F. Sandiumenge, B. Martínez, J. Santiso Front. Phys. ; 4: 41. 2016. 10.3389/fphy.2016.00041.

    We present a single-step route to generate ordered nanocomposite thin films of secondary phase inclusions (Mn3O4) in a pristine perovskite matrix (LaMnO3) by taking advantage of the complex phase diagram of manganese oxides. We observed that in samples grown under vacuum growth conditions from a single LaMnO3 stoichiometric target by Pulsed Laser Deposition, the most favorable mechanism to accommodate Mn2+ cations is the spontaneous segregation of self-assembled wedge-like Mn3O4 ferrimagnetic inclusions inside a LaMnO3 matrix that still preserves its orthorhombic structure and its antiferromagnetic bulk-like behavior. A detailed analysis on the formation of the self-assembled nanocomposite films evidences that Mn3O4 inclusions exhibit an epitaxial relationship with the surrounding matrix that it may be explained in terms of a distorted cubic spinel with slight (~9°) c-axis tilting. Furthermore, a Ruddlesden-Popper La2MnO4 phase, helping to the stoichiometry balance, has been identified close to the interface with the substrate. We show that ferrimagnetic Mn3O4 columns influence the magnetic and transport properties of the nanocomposite by increasing its coercive field and by creating local areas with enhanced conductivity in the vicinity of the inclusions.


  • Misfit Dislocation Guided Topographic and Conduction Patterning in Complex Oxide Epitaxial Thin Films

    Sandiumenge F., Bagués N., Santiso J., Paradinas M., Pomar A., Konstantinovic Z., Ocal C., Balcells L., Casanove M.-J., Martínez B. Advanced Materials Interfaces; 3 (14, 1600106) 2016. 10.1002/admi.201600106. IF: 3.365

    Interfacial dissimilarity has emerged in recent years as the cornerstone of emergent interfacial phenomena, while enabling the control of electrical transport and magnetic behavior of complex oxide epitaxial films. As a step further toward the lateral miniaturization of functional nanostructures, this work uncovers the role of misfit dislocations in creating periodic surface strain patterns that can be efficiently used to control the spatial modulation of mass transport phenomena and bandwidth-dependent properties on a ≈20 nm length scale. The spontaneous formation of surface strain-relief patterns in La0.7Sr0.3MnO3/LaAlO3 films results in lateral periodic modulations of the surface chemical potential and tetragonal distortion, controlling the spatial distribution of preferential nucleation sites and the bandwidth of the epilayer, respectively. These results provide insights into the spontaneous formation of strain-driven ordered surface patterns, topographic and functional, during the growth of complex oxide heterostructures on lengths scales far below the limits achievable through top-down approaches. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim


  • Self-Arranged Misfit Dislocation Network Formation upon Strain Release in La0.7Sr0.3MnO3/LaAlO3(100) Epitaxial Films under Compressive Strain

    Santiso J., Roqueta J., Bagués N., Frontera C., Konstantinovic Z., Lu Q., Yildiz B., Martínez B., Pomar A., Balcells L., Sandiumenge F. ACS Applied Materials and Interfaces; 8 (26): 16823 - 16832. 2016. 10.1021/acsami.6b02896. IF: 7.145

    Lattice-mismatched epitaxial films of La0.7Sr0.3MnO3 (LSMO) on LaAlO3 (001) substrates develop a crossed pattern of misfit dislocations above a critical thickness of 2.5 nm. Upon film thickness increases, the dislocation density progressively increases, and the dislocation spacing distribution becomes narrower. At a film thickness of 7.0 nm, the misfit dislocation density is close to the saturation for full relaxation. The misfit dislocation arrangement produces a 2D lateral periodic structure modulation (Λ≈ 16 nm) alternating two differentiated phases: one phase fully coherent with the substrate and a fully relaxed phase. This modulation is confined to the interface region between film and substrate. This phase separation is clearly identified by X-ray diffraction and further proven in the macroscopic resistivity measurements as a combination of two transition temperatures (with low and high Tc). Films thicker than 7.0 nm show progressive relaxation, and their macroscopic resistivity becomes similar than that of the bulk material. Therefore, this study identifies the growth conditions and thickness ranges that facilitate the formation of laterally modulated nanocomposites with functional properties notably different from those of fully coherent or fully relaxed material. © 2016 American Chemical Society.


  • Strain-induced perpendicular magnetic anisotropy in L a2CoMn O6-É thin films and its dependence on film thickness

    Galceran R., López-Mir L., Bozzo B., Cisneros-Fernández J., Santiso J., Balcells L., Frontera C., Martínez B. Physical Review B; 93 (14, 144417) 2016. 10.1103/PhysRevB.93.144417.

    Ferromagnetic insulating La2CoMnO6-É (LCMO) epitaxial thin films grown on top of SrTiO3 (001) substrates present a strong magnetic anisotropy favoring the out-of-plane (OP) orientation of the magnetization with a large anisotropy field (∼70 kOe for film thickness of about 15 nm). Diminishing oxygen off-stoichiometry of the film enhances the anisotropy. We attribute this to the concomitant shrinkage of the OP cell parameter and to the increasing of the tensile strain of the films. Consistently, LCMO films grown on (LaAlO3)0.3(Sr2AlTaO6)0.7 and LaAlO3 substrates (with a larger OP lattice parameter and compressive stress) display in-plane (IP) magnetic anisotropy. Thus, we link the strong magnetic anisotropy observed in LCMO to the film stress: tensile strain favors perpendicular anisotropy, and compressive stress favors IP anisotropy. We also report on the thickness dependence of the magnetic properties. Perpendicular anisotropy, saturation magnetization, and Curie temperature are maintained over a large range of film thickness. © 2016 American Physical Society.


  • Superionic behavior in the xAgI-(1-x)CsAg2I3 polycrystalline system

    Rodríguez L.A., Zapata J., Vargas R.A., Peña Lara D., Diosa J.E. Journal of Physics and Chemistry of Solids; 93: 126 - 130. 2016. 10.1016/j.jpcs.2016.02.018. IF: 2.048

    A superionic phase behavior (with DC ionic conductivities higher than 0.01 S/cm) has been observed in xAgI-(1-x)CsAg2I3 (x≈0.67) polycrystalline system grown by slow evaporation using AgI and CsI powders (molar ratio Cs/Ag=0.25) as starting salts and an aqueous solution of HI as solvent. The transition from the normal-to- the superionic state is first-order with a hysteretic behavior in temperature centered at about 116 °C as reflected by thermal (DSC) and electrical conductivity measurements. This mixture is composed of CsAg2I3 and AgI crystalline phases and an additional amorphous AgI phase that explains the glassy-type behavior observed in the superionic phase transition. © 2016 Elsevier Ltd. All rights reserved .


  • The Band Gap of BaPrO3 Studied by Optical and Electrical Methods

    Schrade M., Magrasó A., Galeckas A., Finstad T.G., Norby T. Journal of the American Ceramic Society; 99 (2): 492 - 498. 2016. 10.1111/jace.13961. IF: 2.787

    We report on measurements of the electrical and optical properties of BaPrO3. The temperature dependences of the electrical conductivity σ and the Seebeck coefficient α of polycrystalline samples were studied over a wide temperature range (300°C-1050°C). At lower temperatures, the observed charge transport can be described as thermally activated hopping of electron-based small polarons with an activation energy of 0.37 eV. An observed change in temperature dependence of both σ and α around 700°C was observed and interpreted as a transition from extrinsic to intrinsic carrier transport. The intrinsic conduction can be modeled with an apparent electrical band gap of ~2 eV. Optical absorption and emission spectroscopy in the UV-VIS-NIR range revealed a series of characteristic absorption thresholds and the type of optical transitions was identified by combining transmittance and diffuse-reflectance spectroscopy methods. An absorption edge of indirect type with onset at 0.6 eV is attributed to small polaron effects. The higher lying absorption thresholds of direct origin positioned at around 1.8 and 3.8 eV are correlated with thermal activation parameters from electrical measurements and discussed in terms of the band gap of BaPrO3. © 2015 The American Ceramic Society.


  • Thermodynamic conditions during growth determine the magnetic anisotropy in epitaxial thin-films of La0.7Sr0.3MnO3

    Vila-Fungueiriño J.M., Bui C.T., Rivas-Murias B., Winkler E., Milano J., Santiso J., Rivadulla F. Journal of Physics D: Applied Physics; 49 (31, 315001) 2016. 10.1088/0022-3727/49/31/315001.

    The suitability of a particular material for use in magnetic devices is determined by the process of magnetization reversal/relaxation, which in turn depends on the magnetic anisotropy. Therefore, designing new ways to control magnetic anisotropy in technologically important materials is highly desirable. Here we show that magnetic anisotropy of epitaxial thin-films of half-metallic ferromagnet La0.7Sr0.3MnO3 (LSMO) is determined by the proximity to thermodynamic equilibrium conditions during growth. We performed a series of x-ray diffraction and ferromagnetic resonance (FMR) experiments in two different sets of samples: the first corresponds to LSMO thin-films deposited under tensile strain on (0 0 1) SrTiO3 by pulsed laser deposition (PLD; far from thermodynamic equilibrium); the second were deposited by a slow chemical solution deposition (CSD) method, under quasi-equilibrium conditions. Thin films prepared by PLD show fourfold in-plane magnetic anisotropy, with an overimposed uniaxial term. However, the uniaxial anisotropy is completely suppressed in the CSD films. This change is due to a different rotation pattern of MnO6 octahedra to accommodate epitaxial strain, which depends not only on the amplitude of tensile stress imposed by the STO substrate, but also on the growth conditions. Our results demonstrate that the nature and magnitude of the magnetic anisotropy in LSMO can be tuned by the thermodynamic parameters during thin-film deposition. © 2016 IOP Publishing Ltd.


  • Tunneling anisotropic magnetoresistance in La2/3Sr1/3MnO3/LaAlO3/Pt tunnel junctions

    Galceran R., Balcells L., Pomar A., Konstantinović Z., Bagués N., Sandiumenge F., Martínez B. AIP Advances; 6 (4, 045305) 2016. 10.1063/1.4946851. IF: 1.444

    The magnetotransport properties of La2/3Sr1/3MnO3(LSMO)/ LaAlO3(LAO)/Pt tunneling junctions have been analyzed as a function of temperature and magnetic field. The junctions exhibit magnetoresistance (MR) values of about 37%, at H=90 kOe at low temperature. However, the temperature dependence of MR indicates a clear distinct origin than that of conventional colossal MR. In addition, tunneling anisotropic MR (TAMR) values around 4% are found at low temperature and its angular dependence reflects the expected uniaxial anisotropy. The use of TAMR response could be an alternative of much easier technological implementation than conventional MTJs since only one magnetic electrode is required, thus opening the door to the implementation of more versatile devices. However, further studies are required in order to improve the strong temperature dependence at the present stage. © 2016 Author(s).


2015

  • Enhanced conduction and ferromagnetic order at (100)-type twin walls in L a0.7 S r0.3Mn O3 thin films

    Balcells L., Paradinas M., Baguès N., Domingo N., Moreno R., Galceran R., Walls M., Santiso J., Konstantinovic Z., Pomar A., Casanove M.-J., Ocal C., Martínez B., Sandiumenge F. Physical Review B - Condensed Matter and Materials Physics; 92 (7, 075111) 2015. 10.1103/PhysRevB.92.075111. IF: 3.736

    There is increasing evidence supporting the strong potential of twin walls in ferroic materials as distinct, spatially tunable, functional elements in future electronic devices. Here, we report an increase of about one order of magnitude in conductivity and more robust magnetic interactions at (100)-type twin walls in La0.7Sr0.3MnO3 thin films. The nature and microscopic origin of such distinctive behavior is investigated by combining conductive, magnetic, and force modulation scanning force microscopies with transmission electron microscopy techniques. Our analyses indicate that the observed behavior is due to a severe compressive strained state within an ∼1nm slab of material centered at the twin walls, promoting stronger Mn 3d-O2p orbital overlapping leading to a broader bandwidth and enhanced magnetic interactions. © 2015 American Physical Society.


  • Microstructure and ionic conductivity of LLTO thin films: Influence of different substrates and excess lithium in the target

    Aguesse F., Roddatis V., Roqueta J., Garcia P., Pergolesi D., Santiso J., Kilner J.A. Solid State Ionics; 272: 1 - 8. 2015. 10.1016/j.ssi.2014.12.005. IF: 2.561

    The deposition of single phase Li3xLa2/3 - xTiO3 (LLTO) thin films remains very challenging. The growth of the perovskite phase is in competition with the insulating La2Ti2O7 phase when prepared at high oxygen pressure by PLD. Nevertheless, we have achieved epitaxial growth of LLTO on different (001) oriented substrates such as LaAlO3, SrTiO3 and MgO despite a large lattice mismatch of up to + 8.8%. We also determined the percentage of lithium excess in the target necessary to reach a maximum ionic conductivity. However, the presence of the blocking La2Ti2O7 phase strongly hinders the lithium ion migration and reduces the total conductivity compared to bulk properties. © 2014 Elsevier B.V.


  • Nanostructured Ti thin films by magnetron sputtering at oblique angles

    Alvarez R., Garcia-Martin J.M., Garcia-Valenzuela A., Macias-Montero M., Ferrer F.J., Santiso J., Rico V., Cotrino J., Gonzalez-Elipe A.R., Palmero A. Journal of Physics D: Applied Physics; 49 (4, 045303) 2015. 10.1088/0022-3727/49/4/045303. IF: 2.721

    The growth of Ti thin films by the magnetron sputtering technique at oblique angles and at room temperature is analysed from both experimental and theoretical points of view. Unlike other materials deposited in similar conditions, the nanostructure development of the Ti layers exhibits an anomalous behaviour when varying both the angle of incidence of the deposition flux and the deposition pressure. At low pressures, a sharp transition from compact to isolated, vertically aligned, nanocolumns is obtained when the angle of incidence surpasses a critical threshold. Remarkably, this transition also occurs when solely increasing the deposition pressure under certain conditions. By the characterization of the Ti layers, the realization of fundamental experiments and the use of a simple growth model, we demonstrate that surface mobilization processes associated to a highly directed momentum distribution and the relatively high kinetic energy of sputtered atoms are responsible for this behaviour. © 2016 IOP Publishing Ltd.


  • On the development of proton ceramic fuel cells based on Ca-doped LaNbO4 as electrolyte

    Norby T., Magrasó A. Journal of Power Sources; 282: 28 - 33. 2015. 10.1016/j.jpowsour.2015.02.027. IF: 6.217

    We review the key properties of Ca-doped LaNbO4 (LCNO) and related materials for use as proton conducting electrolyte, from the discovery of its proton conductivity, through developments of synthesis and production, anodes and cathodes, to demonstrations of it in laboratory fuel cells, exemplified through published and new results from a range of collaborative projects in Norway and Europe the last years. Important new knowledge has been obtained concerning the reliable synthesis of line compounds like LaNbO4, B-site doping and co-doping, grain boundary resistance, phase transformations, thin film fabrication, and electrodes for proton conducting ceramics. However, as LCNO still requires films too thin for reliable fabrication of large areas and operation over prolonged times, and since cathodes with acceptable electrocatalytic performance have not been identified, one must conclude that high-power fuel cells (and steam electrolysers) based on LCNO are not viable. © 2015 Published by Elsevier B.V.


  • Persistence of ferroelectricity above the Curie temperature at the surface of Pb(Z n1/3 N b2/3) O3-12%PbTi O3

    Domingo N., Bagués N., Santiso J., Catalan G. Physical Review B - Condensed Matter and Materials Physics; 91 (9, 094111) 2015. 10.1103/PhysRevB.91.094111. IF: 3.736

    Relaxor-based ferroelectrics have been known for decades to possess a relatively thick surface layer ("skin") that is distinct from its interior. Yet while there is consensus about its existence, there are controversies about its symmetry, phase stability, and origin. In an attempt to clarify these issues, we have examined the surface layer of PZN-12%PT. While the bulk transitions from a ferroelastically twinned tetragonal ferroelectric state with in-plane polarization to a cubic paraphase at Tc=200C, the skin layer shows a robust labyrinthine nanodomain structure with out-of-plane polarization that persists hundreds of degrees above the bulk Curie temperature. Cross-sectional transmission electron microscopy analysis shows that the resilience of the skin's polarization is correlated with a compositional imbalance: lead vacancies at the surface are charge-compensated by niobium enrichment; the excess of Nb5+ - a small ion with d0 orbital occupancy - stabilizes the ferroelectricity of the skin layer. © 2015 American Physical Society.


  • Reduced long term electrical resistance in Ce/Co-coated ferritic stainless steel for solid oxide fuel cell metallic interconnects

    Magraso A., Falk-Windisch H., Froitzheim J., Svensson J.-E., Haugsrud R. International Journal of Hydrogen Energy; 40 (27): 8579 - 8585. 2015. 10.1016/j.ijhydene.2015.04.147. IF: 3.313

    The present study is focused on the influence of selected coatings on a ferritic stainless steel (Sanergy HT™, Sandvik) on the evolution of the area specific resistance (ASR) as a function of time at high temperature. The samples are exposed in humidified air at 850 °C for up to 4200 h. It combines long-term ASR measurements with the thermogravimetric behavior and microstructural analysis of the cross sections by scanning electron microscopy. The results show that uncoated and Co-coated Sanergy HT™ exhibit similar oxidation kinetics and comparable ASRs, while a combined Ce/Co coating improves oxidation resistance and, consequently, reduces the ASR significantly. Other reports have earlier shown that Co- (and Ce/Co)-coated Sanergy HT™ reduces the evaporation of volatile chromium species. Overall, the study indicates that Ce/Co-coatings will render substantially improved performance for ferritic steel interconnects for solid oxide fuel cells. Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.


  • Strain-Engineered Ferromagnetism in LaMnO3 Thin Films

    Roqueta J., Pomar A., Balcells L., Frontera C., Valencia S., Abrudan R., Bozzo B., Konstantinović Z., Santiso J., Martínez B. Crystal Growth and Design; 15 (11): 5332 - 5337. 2015. 10.1021/acs.cgd.5b00884. IF: 4.891

    A systematic study of the growth process of LaMnO3 (LMO) thin films, by pulsed laser deposition, on top of SrTiO3 substrates under different oxygen partial pressures (PO 2) is reported. It is found that the accommodation of the orthorhombic LMO phase onto the cubic STO structure, i.e., the amount of structural strain, is controlled by the background oxygen pressure. We demonstrate that magnetic behavior can be continuously tuned from robust ferromagnetic (FM) ordering to an antiferromagnet. These results strongly point to a strain-induced selective orbital occupancy as the origin of the observed FM behavior, in agreement with recent theoretical calculations. © 2015 American Chemical Society.


  • Tailoring thermal conductivity by engineering compositional gradients in Si1−xGe x superlattices

    Ferrando-Villalba P., Lopeandía A.F., Alvarez F.X., Paul B., de Tomás C., Alonso M.I., Garriga M., Goñi A.R., Santiso J., Garcia G., Rodriguez-Viejo J. Nano Research; 8 (9): 2833 - 2841. 2015. 10.1007/s12274-015-0788-9. IF: 7.010

    The transport properties of artificially engineered superlattices (SLs) can be tailored by incorporating a high density of interfaces in them. Specifically, SiGe SLs with low thermal conductivity values have great potential for thermoelectric generation and nano-cooling of Si-based devices. Here, we present a novel approach for customizing thermal transport across nanostructures by fabricating Si/Si1−xGex SLs with well-defined compositional gradients across the SiGe layer from x = 0 to 0.60. We demonstrate that the spatial inhomogeneity of the structure has a remarkable effect on the heat-flow propagation, reducing the thermal conductivity to ∼2.2 W·m−1·K−1, which is significantly less than the values achieved previously with non-optimized long-period SLs. This approach offers further possibilities for future applications in thermoelectricity. [Figure not available: see fulltext.] © 2015, Tsinghua University Press and Springer-Verlag Berlin Heidelberg.


2014

  • Chemical strain and oxidation-reduction kinetics of epitaxial thin films of mixed ionic-electronic conducting oxides determined by x-ray diffraction

    Moreno, R.; Zapata, J.; Roqueta, J.; Bagués, N.; Santiso, J. Journal of the Electrochemical Society; 161 (11): F3046 - F3051. 2014. 10.1149/2.0091411jes. IF: 2.859


  • Engineering the microstructure and magnetism of La2CoMnO6-δ thin films by tailoring oxygen stoichiometry

    Galceran, R.; Frontera, C.; Balcells, Ll.; Cisneros-Fernández, J.; López-Mir, L.; Roqueta, J.; Santiso, J.; Bagués, N.; Bozzo, B.; Pomar, A.; Sandiumenge, F.; Martínez, B. Applied Physics Letters; 2014. 10.1063/1.4904410. IF: 3.515


  • Growth kinetics engineered magnetoresistance response in La 2/3Sr1/3MnO3 thin films

    Pomar, A.; Santiso, J.; Sandiumenge, F.; Oqueta, J.; Bozzo, B.; Frontera, C.; Balcells, L.; Martínez, B.; Konstantinovic, Z. Applied Physics Letters; 2014. 10.1063/1.4871984. IF: 3.515


  • Interfaces and nanostructures of functional oxide octahedral framework structures

    Sandiumenge, F.; Bagués, N. ; Santiso, J. Frontiers; 2014. 10.3389/fmats.2014.00013. IF: 0.000


2013

  • Anisotropic 18O tracer diffusion in epitaxial films of GdBaCo2O5+δ cathode material with different orientations

    Zapata, J.; Burriel, M.; García, P.; Kilner, J.A.; Santiso, J. Journal of Materials Chemistry A; 1: 7408 - 7414. 2013. 10.1039/c3ta10749c. IF: 6.108


  • Chemical strain kinetics induced by oxygen surface exchange in epitaxial films explored by time-resolved X-ray diffraction

    Moreno, R.; García, P.; Zapata, J.; Roqueta, J.; Chaigneau, J.; Santiso, J. Chemistry of Materials; 25: 3640 - 3647. 2013. 10.1021/cm401714d. IF: 8.238


  • Competing misfit relaxation mechanisms in epitaxial correlated oxides

    Sandiumenge, F.; Santiso, J.; Balcells, L.; Konstantinovic, Z.; Roqueta, J.; Pomar, A.; Espinós, J.P.; Martínez, B. Physical Review Letters; 110 2013. 10.1103/PhysRevLett.110.107206. IF: 7.943


  • Low-temperature, solution-processed, layered V2O5 hydrate as the hole-transport layer for stable organic solar cells

    Terán-Escobar, G.; Pampel, J.; Caicedo, J.M.; Lira-Cantú, M. Energy and Environmental Sciences; 6 (10): 3088 - 3098. 2013. 10.1039/c3ee42204f. IF: 11.653


  • Magnetic properties of single crystalline expanded austenite obtained by plasma nitriding of austenitic stainless steel single crystals

    Menéndez, E.; Templier, C.; Garcia-Ramirez, P.; Santiso, J.; Vantomme, A.; Temst, K.; Nogués, J. ACS applied materials & interfaces; 5: 10118 - 10126. 2013. 10.1021/am402773w. IF: 5.008


  • Processing and immobilization of chondroitin-4-sulphate by UV laser radiation

    György, E.; Pérez del Pino, A.; Roqueta, J.; Sánchez, C.; Oliva, A.G. Colloids and Surfaces B: Biointerfaces; 104: 169 - 173. 2013. 10.1016/j.colsurfb.2012.11.044. IF: 3.554


  • Reduction of the deposition temperature of high quality EuO films on Yttria Stabilized Zirconia by incorporating an MgO buffer layer

    Moder, I.; Garcia, G.; Santiso, J.; Moodera, J.S.; Miao, G.X.; Lopeandía, A.F.; Rodríguez-Viejo, J. Thin Solid Films; 531: 466 - 470. 2013. 10.1016/j.tsf.2012.12.030. IF: 1.604


  • Self-assembled pit arrays as templates for the integration of Au nanocrystals in oxide surfaces

    Konstantinovic, Z.; Sandiumenge, F.; Santiso, J.; Balcells, L.; Martínez, B. Nanoscale; 5: 1001 - 1008. 2013. 10.1039/c2nr33181k. IF: 6.233


  • Thickness evolution of the twin structure and shear strain in LSMO films

    Santiso, J.; Balcells, L.; Konstantinovic, Z.; Roqueta, J.; Ferrer, P.; Pomar, A.; Martínez, B.; Sandiumenge, F. CrystEngComm; 15: 3908 - 3918. 2013. 10.1039/c3ce40085a. IF: 3.879


2012

  • Epitaxial films of the proton-conducting Ca-doped LaNbO4 material and a study of their charge transport properties

    Santiso, J. Solid State Ionics; in press: in-press. 2012. 10.1016/j.ssi.2012.03.033.


  • Epitaxial growth of Nb-doped SrTiO3 films by pulsed laser deposition

    Santiso, J.; Roqueta, J. Applied Surface Science; in-press: in-press. 2012. 10.1016/j.apsusc.2012.02.041.


  • Interface structure governed by plastic and structural dissimilarity in perovskite La 0.7Sr 0.3MnO 3 nanodots on rock-salt MgO substrates

    Abellán, P.; Zabaleta, J.; Santiso, J.; Casanove, M.-J.; Dix, N.; Aguiar, J.; Browning, N.D.; Mestres, N.; Puig, T.; Obradors, X.; Sandiumenge, F. Applied Physics Letters; 100 2012. 10.1063/1.3687692.


  • Pinhole-free YSZ self-supported membranes for micro solid oxide fuel cell applications

    Santiso, J. Solid State Ionics; in-press: in-press. 2012. 10.1016/j.ssi.2011.09.011.


2011

  • Deposition and Characterisation of epitaxial films for SOFCs.

    Santiso, J.; Burriel, M. Journal of Solid State Electrochemistry; 2011. 10.1007/s10008-010-1214-6.


  • Domain structure and Raman modes in PbTiO3.

    Santiso, J. Phase Transitions; 2011. 10.1080/01411594.2011.552433.


  • Heteroepitaxial orientation control of YSZ thin films by selective growth on SrO-, TiO2-terminated SrTiO3 crystal surfaces

    Cavallaro, A.; Ballesteros, B.; Bachelet, R.; Santiso, J. CrystEngComm; 13: 1625 - 1631. 2011. 10.1039/c0ce00606h.


2010

  • Advances in layered oxide cathodes for intermediate temperature solid oxide fuel cells

    Tarancón, A.; Burriel, M.; Santiso, J.; Skinner, S.J.; Kilner, J.A. Journal of Materials Chemistry; 20: 3799 - 3813. 2010. 10.1039/b922430k.


  • Anulado --- Electronic nature of the enhanced conductivity in YSZ-STO multilayers deposited by PLD

    Cavallaro, A. ; Burriel, M.; Roqueta, J.; Apostolidis, A.; Bernardi, A.; Tarancón, A.; Srinivasan, R.; Cook, S. N.; Fraser, H. L.; Kilner, J. A.; McComb, D. W.; Santiso, J. Solid State Ionics; 181: 592 - 601. 2010. .


  • BSCF epitaxial thin films: Electrical transport and oxygen surface exchange

    Burriel, M.; Niedrig, C.; Menesklou, W.; Wagner, S.F.; Santiso, J.; Ivers-Tiffée, E. Solid State Ionics; 181: 602 - 608. 2010. 10.1016/j.ssi.2010.03.005.


  • Defect structure, charge transport mechanisms, and strain effects in Sr4Fe6O12+δ epitaxial thin films

    Solís, C.; Jung, W.; Tuller, H.L.; Santiso, J. Chemistry of Materials; 22: 1452 - 1461. 2010. 10.1021/cm902957r.


  • Electrical characterization of thermomechanically stable YSZ membranes for micro solid oxide fuel cells applications

    Garbayo, I.; Tarancón, A.; Santiso, J.; Peiró, F.; Alarcón-LLadó, E.; Cavallaro, A.; Gràcia, I.; Cané, C.; Sabaté, N. Solid State Ionics; 181: 322 - 331. 2010. 10.1016/j.ssi.2009.12.019.


  • Electronic nature of the enhanced conductivity in YSZ-STO multilayers deposited by PLD

    Cavallaro, A.; Burriel, M.; Roqueta, J.; Apostolidis, A.; Bernardi, A.; Tarancón, A.; Srinivasan, R.; Cook, S.N.; Fraser, H.L.; Kilner, J.A.; McComb, D.W.; Santiso, J. Solid State Ionics; 181: 592 - 601. 2010. 10.1016/j.ssi.2010.03.014.


  • Influence of the microstructure on the high-temperature transport properties of GdBaCo2O5.5+δ epitaxial films

    Burriel, M.; Casas-Cabanas, M.; Zapata, J.; Tan, H.; Verbeeck, J.; Solís, C.; Roqueta, J.; Skinner, S.J.; Kilner, J.A.; Van Tendeloo, G.; Santiso, J. Chemistry of Materials; 22: 5512 - 5520. 2010. 10.1021/cm101423z.


  • Kinetic versus strain formation of self-organized nanoholes in manganite thin films

    Konstantinovic; , Z.; Santiso, J.; Balcells, L.; Martínez, B. Nanotechnology; 21 2010. 10.1088/0957-4484/21/46/465601.


  • Magnetic, structural properties and B-site order of two epitaxial La2CoMnO6 films with perpendicular out-of-plane orientation.

    Barón-González, A. J.; Frontera, C.; García-Muñoz, J. L.; Roqueta, J.; Santiso, J. Journal of Physics: Conference Series; 200: 92002. 2010. 10.1088/1742-6596/200/9/092002.


  • Residual Stress of Free-Standing Membranes of Yttria-Stabilized Zirconia for Micro Solid Oxide Fuel Cell Applications

    Tarancón, A.; Sabaté, N.; Cavallaro, A.; Gràcia, I.; Roqueta, J.; Garbayo, I.; Esquivel, J.P.; Garcia, G.; Cané, C.; Santiso, J. Journal of Nanoscience and Nanotechnology; 10 (2): 1327 - 1337. 2010. 10.1166/jnn.2010.1837.


  • Two-dimensional wetting: The role of atomic steps on the nucleation of thin water films on BaF2 (111) at ambient conditions

    Cardellach, M.; Verdaguer, A.; Santiso, J.; Fraxedas, J. Journal of Chemical Physics; 132 2010. 10.1063/1.3456698.


2009

  • Effects of stress and morphology on the resistivity and critical temperature of room-temperature-sputtered mo thin films

    Fàbrega, L.; Fernández-Martínez, I.; Parra-Borderías, M.; Gil, O.; Camón, A.; González-Arrabal, R.; Sesé, J.; Santiso, J.; Costa-Krämer, J.-L.; Briones, F. IEEE Transactions on Applied Superconductivity; 19: 3779 - 3785. 2009. 10.1109/TASC.2009.2027609.


  • Enhanced thermal stability of Pt electrodes for flat epitaxial biferroic- YMnO3 /Pt heterostructures

    Bachelet, R.; Muralidharan, R.; Rigato, F.; Dix, N.; Martí, X.; Santiso, J.; Sánchez, F.; Fontcuberta, J. Applied Physics Letters; 95 2009. 10.1063/1.3259417.


  • Mo-Based Proximity Bilayers for TES: Microstructure and Properties

    Fabrega, L.; Fernandez-Martinez, I.; Gil, O.; Parra-Borderias, Maria; Camon, A.; Costa-Kramer, J.-L.; Gonzalez-Arrabal, R.; Sese, J.; Briones, F.; Santiso, J.; Peiro, Francesca IEEE Transactions on Applied Superconductivity; 2009. 10.1109/TASC.2009.2019052.


  • Residual stress estimation in ferroelectric PbTiO3 thin films by Raman spectroscopy

    Bartasyte, A.; Margueron, S.; Kreisel, J.; Bourson, P.; Chaix-Pluchery, O.; Rapenne-Homand, L.; Santiso, J.; Jimenez, C.; Abrutis, A.; Weiss, F.; Fontana, M.D. Physical Review B - Condensed Matter and Materials Physics; 79 2009. 10.1103/PhysRevB.79.104104.


  • Self-assembly of srtio3(001) chemical-terminations: A route for oxide-nanostructure fabrication by selective growth

    Bachelet, R.; Sánchez, F.; Santiso, J.; Munuera, C.; Ocal, C.; Fontcuberta, J. Chemistry of Materials; 21: 2494 - 2498. 2009. 10.1021/cm900540z.


  • Self-organization processes in highly epitaxial La2/3Sr 1/3MnO3 thin films grown on SrTiO3 (001) substrates

    Konstantinovic, Z.; Santiso, J.; Colson, D.; Forget, A.; Balcells, Ll.; Martínez, B. Journal of Applied Physics; 105 2009. 10.1063/1.3093862.


  • Strain-driven self-assembled network of antidots in complex oxide thin films

    Konstantinovic, Z.; Santiso, J.; Balcells, L.; Martínez, B. Small; 5: 265 - 271. 2009. 10.1002/smll.200800814.


2008

  • Anisotropic oxygen diffusion properties in epitaxial thin films of La 2NiO4+δ

    Burriel, M.; Garcia, G.; Santiso, J.; Kilner, J.A.; Chater, R.J.; Skinner, S.J. Journal of Materials Chemistry; 18: 416 - 422. 2008. 10.1039/b711341b.


  • Electrical conductivity and oxygen exchange kinetics of La2 NiO4+δ thin films grown by chemical vapor deposition

    Garcia, G.; Burriel, M.; Bonanos, N.; Santiso, J. Journal of the Electrochemical Society; 155: P28 - P32. 2008. 10.1149/1.2829900.


  • Enhancing total conductivity of La2NiO4+δ epitaxial thin films by reducing thickness

    Burriel, M.; Santiso, J.; Rossell, M.D.; Van Tendeloo, G.; Figueras, A.; Garcia, G. Journal of Physical Chemistry C; 112: 10982 - 10987. 2008. 10.1021/jp7101622.


  • Microstructure and high temperature transport properties of high quality epitaxial SrFeO3 - δ films

    Solís, C.; Rossell, M.D.; Garcia, G.; Figueras, A.; Van Tendeloo, G.; Santiso, J. Solid State Ionics; 179: 1996 - 1999. 2008. 10.1016/j.ssi.2008.06.004.


  • Reversible growth-mode transition in SrRuO3 epitaxy

    Bachelet, R.; Sánchez, F.; Santiso, J.; Fontcuberta, J. Applied Physics Letters; 93 2008. 10.1063/1.3001932.


  • Unusual strain accommodation and conductivity enhancement by structure modulation variations in Sr4Fe6O12+δ epitaxial films

    Solís, C.; Rossell, M.D.; Garcia, G.; Van Tendeloo, G.; Santiso, J. Advanced Functional Materials; 18: 785 - 793. 2008. 10.1002/adfm.200701011.


2007

  • Biomolecular papain thin films growth by laser techniques

    György, E.; Santiso, J.; Figueras, A.; Socol, G.; Mihailescu, I.N. Journal of Materials Science: Materials in Medicine; 18: 1643 - 1647. 2007. 10.1007/s10856-007-3055-0.


  • Combinatorial synthesis and hydrogenation of Mg/Al libraries prepared by electron beam physical vapor deposition

    Garcia, G.; Doménech-Ferrer, R.; Pi, F.; Santiso, J.; Rodríguez-Viejo, J. Journal of Combinatorial Chemistry; 9: 230 - 236. 2007. 10.1021/cc060131h.


  • Enhanced high-temperature electronic transport properties in nanostructured epitaxial thin films of the Lan+1NinO3n+1 Ruddlesden-Popper series (n = 1, 2, 3, ∞)

    Burriel, M.; Garcia, G.; Rossell, M.D.; Figueras, A.; Van Tendeloo, G.; Santiso, J. Chemistry of Materials; 19: 4056 - 4062. 2007. 10.1021/cm070804e.


  • Raman spectroscopy and X-ray diffraction studies of stress effects in PbTiO3 thin films

    Santiso, J IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control; 54 (12): 2623 - 2631. 2007. 10.1109/TUFFC.2007.589.


  • Synthesis of undoped and Ni doped InTaO4 photoactive thin films by metal organic chemical vapor deposition

    McSporran, N.; Rico, V.; Borrás, A.; González-Elipe, A.R.; Sauthier, G.; György, E.; Santiso, J.; Garcia, G.; Figueras, A.; Parafianovic, L.; Abrutis, A. Surface and Coatings Technology; 201: 9365 - 9368. 2007. 10.1016/j.surfcoat.2007.04.049.


2006

  • Au cluster growth on ZnO thin films by pulsed laser deposition

    György, E.; Santiso, J.; Figueras, A.; Giannoudakos, A.; Kompitsas, M.; Mihailescu, I.N.; Ducu, C. Applied Surface Science; 252: 4429 - 4432. 2006. 10.1016/j.apsusc.2005.07.148.


  • Thickness-dependent transport properties of Sr4Fe 6O13 epitaxial thin films

    Pardo, J.A.; Santiso, J.; Solís, C.; Garcia, G.; Figueras, A.; Rossell, M.D. Solid State Ionics; 177: 423 - 428. 2006. 10.1016/j.ssi.2005.11.024.


2005

  • Co3O4 protective coatings prepared by pulsed injection metal organic chemical vapour deposition

    Burriel, M.; Garcia, G.; Santiso, J.; Hansson, A.N.; Linderoth, S.; Figueras, A. Thin Solid Films; 473: 98 - 103. 2005. 10.1016/j.tsf.2004.07.081.


  • Growth kinetics, composition, and morphology of Co3O4 thin films prepared by pulsed liquid-injection MOCVD

    Burriel, M.; Garcia, G.; Santiso, J.; Abrutis, A.; Saltyte, Z.; Figueras, A. Chemical Vapor Deposition; 11: 106 - 111. 2005. 10.1002/cvde.200406320.


  • Growth of Al doped ZnO thin films by a synchronized two laser system

    E. György; Santiso, J.; A. Giannoudakos; M. Kompitsas; I.N. Mihailescu; D. Pantelica Applied Surface Science; 248 (01-abr.): 147 - 150. 2005. 10.1016/j.apsusc.2005.03.017.


  • Morphology evolution and local electric properties of Au nanoparticles on ZnO thin films

    György, E.; Santiso, J.; Figueras, A.; Giannoudakos, A.; Kompitsas, M.; Mihailescu, I.N. Journal of Applied Physics; 98 2005. 10.1063/1.2089166.


  • Self-doped titanium oxide thin films for efficient visible light photocatalysis: An example: Nonylphenol photodegradation

    Justicia, I.; Garcia, G.; Vázquez, L.; Santiso, J.; Ordejón, P.; Battiston, G.; Gerbasi, R.; Figueras, A. Sensors and Actuators, B: Chemical; 109: 52 - 56. 2005. 10.1016/j.snb.2005.03.021.


  • Strain relaxation and oxygen superstructure modulation in epitaxial Sr4Fe6O13±¿ films

    Santiso, J.; Pardo, J.A.; Solís, C.; Garcia, G.; Figueras, A.; Rossell, M.D.; Van Tendeloo, G. Applied Physics Letters; 86 (13): 132105. 2005. 10.1063/1.1886264.


2004

  • Crecimiento de películas delgadas de membranas de conducción iónica mediante la técnica PIMOCVD

    Santiso, J.; Santiso J. Boletin de la Sociedad Espanola de Ceramica y Vidrio; 43 (2): 448 - 451. 2004. .


  • Epitaxial growth of YSZ films prepared by pulsed injection MOCVD

    Garcia, G.; Santiso, J.; Pardo, J.A.; Figueras, A. Applied Surface Science; 233: 191 - 196. 2004. 10.1016/j.apsusc.2004.03.237.


  • Epitaxial Sr4Fe6O 13±δ films obtained by pulsed laser deposition

    Pardo, J.A.; Santiso, J.; Solís, C.; Garcia, G.; Figueras, A.; Rossell, M.D.; Van Tendeloo, G. Journal of Crystal Growth; 262: 334 - 340. 2004. 10.1016/j.jcrysgro.2003.10.037.


  • Structure and microstructure of epitaxial Sr4Fe 6O13±δ films on SrTiO3

    Rossell, M.D.; Abakumov, A.M.; Van Tendeloo, G.; Pardo, J.A.; Santiso, J. Chemistry of Materials; 16: 2578 - 2584. 2004. 10.1021/cm0498234.


  • YSZ thin films deposited on NiO-CSZ anodes by pulsed injection MOCVD for intermediate temperature SOFC applications

    Garcia, G.; Merino, R.I.; Orera, V.M.; Larrea, A.; Peña, J.I.; Laguna-Bercero, M.Á.; Pardo, J.Á.; Santiso, J.; Figueras, A. Chemical Vapor Deposition; 10: 249 - 252. 2004. 10.1002/cvde.200304173.