Disentangling epitaxial growth mechanisms of solution derived functional oxide thin films

This study investigates the mechanisms of epitaxial development and functional properties of oxide thin films (Ce0.9Zr0.1O2−y, LaNiO3, and Ba0.8Sr0.2TiO3) grown on single crystal substrates (Y2O3:ZrO2, LaAlO3, and SrTiO3) by the chemical solution deposition approach. Rapid thermal annealing furnaces are very powerful tools in this study providing valuable information of the early stages of nucleation, the kinetics of epitaxial film growth, and the coarsening of nanocrystalline phases. Advanced transmission electron microscopies, X-ray diffraction, and atomic force microscopy are employed to investigate the film microstructure and morphology, microstrain relaxation, and epitaxial crystallization. This study demonstrates that the isothermal evolution toward epitaxial film growth follows a self-limited process driven by atomic diffusion, and surface and interface energy minimization. All investigated oxides experience a transformation from the polycrystalline to the epitaxial phase. This study unequivocally evidences that the film thickness highly influences the epitaxial crystallization rate due to the competition between heterogeneous and homogeneous nucleation barriers and the fast coarsening of polycrystalline grains as compared to epitaxial growth. The investigated films possess good functional properties, and this study successfully confirms an improvement at long annealing times that can be correlated with grain boundary healing processes. Thick epitaxial films can be crystallized by growing sequential individual epitaxial layers.We acknowledge financial support from Spanish Ministry of Economy and Competitiveness through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496), CONSOLIDER Excellence Network (MAT2015-68994-REDC), COACHSUPENERGY project (MAT2014-56063-C2-1-R, co-financed by the European Regional Development Fund), and the projects MAT2011-28874-C02-01, ENE2014-56109-C3-3-R and Consolider Nanoselect (CSD2007-00041), and from the Catalan Government (2014-SGR-753 and Xarmae). AQ and MdlM are also grateful for JAE-Predoc fellowship from CSIC (E-08-2012-1321248 and E-08-2013-1028356, co-financed by the European Social Fund).Peer Reviewe

Ultrafast crystallization of Ce0.9Zr0.1O2-y epitaxial films on flexible technical substrates by pulsed laser irradiation of chemical solution derived precursor layers

© 2015 American Chemical Society. The epitaxial growth of Ce0.9Zr0.1O2-y (CZO) thin-films on yttria-stabilized zirconia (YSZ) (001) single crystal and YSZ (001)/stainless steel (YSZ/SS) technological substrates is investigated by pulsed laser irradiation of solution-derived cerium-zirconium precursor layers using a UV Nd:YAG laser source at atmospheric conditions. The influence of laser processing parameters on the morphological and structural properties of the obtained films is studied by atomic force and transmission electron microscopies, as well as X-ray diffractometry. The analyses performed demonstrate that laser treatments enable the epitaxial growth of tens of nanometers thick CZO films with a crystallization kinetic process several orders of magnitude faster than that of conventional thermal annealing. Fully epitaxial films are attained using stainless steel (SS) flexible tapes as a substrate. Even though photochemical mechanisms are not fully discarded, it is concluded that photothermal processes are the main contribution responsible for the fast epitaxial crystallization.This work was financed by the Ministry of Economy and Competitiveness under the projects MAT2011-28874-C02-01, MAT2014-51778-C2-1-R and Consolider Nanoselect CSD2007-00041, by Generalitat de Catalunya (2009 SGR 770, 2014 SGR 753 and Xarmae) and by the Spanish National Research Council under the Contract No. 200960I015. AQ and MdlM are also grateful for JAE-Predoc fellowship and European Social Fund program. We acknowledge Bruker Corporation for the supply of the technical substrates through the NMP3-LA-2012-280432 project.Peer Reviewe

Ultrafast epitaxial growth kinetics in functional oxide thin films grown by pulsed laser annealing of chemical solutions

The crystallization process and physical properties of different functional oxide thin films (CeZrO, LaNiO, BaSrTiO, and LaSrMnO) on single crystal substrates (YO:ZrO, LaAlO, and SrTiO) are studied by pulsed laser annealing (PLA). A Nd:YAG laser source (λ = 266 nm, 10 Hz and τ ∼3 ns) is employed to crystallize chemical solution deposited (CSD) amorphous/nanocrystalline films under atmospheric conditions. We provide new insight on the influence of photochemical and photothermal interactions on the epitaxial crystallization kinetics of oxide thin films during the transformation from amorphous/polycrystalline material (i.e., atomic diffusion, epitaxial growth rates, and activation energies of nucleation and crystallization). The epitaxial growth is investigated by varying the laser fluence and the applied number of pulses. The morphology, structure, and epitaxial evolution of films are evaluated by means of atomic force and transmission electron microscopies and X-ray diffraction. Highly epitaxial oriented films of 20-40 nm in thickness are obtained by PLA. The crystallization kinetics of laser treatments is determined to be orders of magnitude faster than thermal treatments with similar activation energies (1.5-4.1 eV), mainly due to the large temperature gradients inducing modified atomic diffusion mechanisms derived mainly from photothermal interactions, as well as a minor contribution of photochemical effects. The fast heating rates achieved by PLA also contribute to the fast epitaxial growth due to reduced coarsening of polycrystalline material. The measurement of the physical properties (electrical resistivity and magnetism) of laser processed CSD films has revealed significantly good functionalities, close to those of thermally grown films, but with much shorter processing times.We acknowledge financial support from Spanish Ministry of Economy and Competitiveness through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2013-0295 and SEV-2015- 0496), CONSOLIDER Excellence Network (MAT2015-68994-REDC), COACHSUPENERGY project (MAT2014-51778-C2-1-R, co-financed by the European Regional Development Fund), and the projects MAT2011-28874-C02-01, ENE2014-56109-C3-3-R and Consolider Nanoselect CSD2007-00041, and from the Catalan Government with 2014-SGR-753, 2014-SGR-1638 and Xarmae. AQ and MdlM are also grateful to CSIC and European Social Fund program for JAE-Predoc fellowships (E-08-2012-1321248 and E-08-2013-1028356).Peer Reviewe

Growth of ferroelectric Ba0.8Sr0.2TiO3 epitaxial films by UV pulsed laser irradiation of chemical solution derived precursor layers

© 2015 AIP Publishing LLC. Highly crystalline epitaxial Ba0.8Sr0.2TiO3 (BST) thin-films are grown on (001)-oriented LaNiO3-buffered LaAlO3 substrates by pulsed laser irradiation of solution derived barium-zirconium-titanium precursor layers using a UV Nd:YAG laser source at atmospheric conditions. The structural analyses of the obtained films, studied by X-ray diffractometry and transmission electron microscopy, demonstrate that laser processing allows the growth of tens of nm-thick BST epitaxial films with crystalline structure similar to that of films obtained through conventional thermal annealing methods. However, the fast pulsed nature of the laser employed leads to crystallization kinetic evolution orders of magnitude faster than in thermal treatments. The combination of specific photothermal and photochemical mechanisms is the main responsible for the ultrafast epitaxial laser-induced crystallization. Piezoresponse microscopy measurements demonstrate equivalent ferroelectric behavior in laser and thermally annealed films, being the piezoelectric constant ∼25 pm V-1.This work was financed by the Ministry of Economy and Competitiveness under the Project Nos. MAT2011-28874-C02-01, ENE2014-56109-C3-3-R, and MAT2014-51778-C2-1-R and Consolider Nanoselect CSD2007-00041 by Generalitat de Catalunya (2009 SGR 770, 2014 SGR 753 and Xarmae) and by the Spanish National Research Council under the Contract No. 200960I015. A.Q. and M.d.l.M. are also grateful for JAE-Predoc fellowship and European Social Fund program. Fruitful discussions with Dr. Susagna Ricart for solution synthesis are also acknowledged.Peer Reviewe

Effectiveness of two video-based multicomponent treatments for fibromyalgia : The added value of cognitive restructuring and mindfulness in a three-arm randomised controlled trial

Acord transformatiu CRUE-CSICUTP en procés de revisióBackground/objectives: The aim of this study was to examine the effectiveness of two video-based multicomponent programs (FIBROWALK) and the Multicomponent Physiotherapy Program (MPP) for patients with fibromyalgia (FM) compared to treatment-as-usual (TAU) only. We posit that FIBROWALK, due to inclusion of specific psychological ingredients (cognitive restructuring and mindfulness), can produce additional clinical benefits when compared to TAU or MPP alone. Methods: A total of 330 patients with FM were recruited and randomly allocated (1:1:1) to TAU only, TAU + FIBROWALK, or TAU + MPP. FIBROWALK and MPP consisted of weekly videos on pain neuroscience education, therapeutic exercise and self-management patient education, but only the FIBROWALK intervention provided cognitive restructuring and mindfulness. Both programs were structurally equivalent. Between-group differences in functional impairment, pain, kinesiophobia, anxious-depressive symptoms and physical functioning were evaluated at post-treatment following Intention-To-Treat and complete-case approaches. Results: Compared to TAU only, individuals in the FIBROWALK arm showed larger improvements in all clinical outcomes; similarly, participants in the MPP program also showed greater improvements in functional impairment, perceived pain, kinesiophobia, depressive symptoms compared to TAU only. The FIBROWALK intervention showed superior effects in improving pain, anxiety and depressive symptoms and physical functioning compared to MPP. Conclusions: This RCT supports the short-term effectiveness of the video-based multicomponent programs FIBROWALK and MPP for FM and provides evidence that cognitive-behavioural and mindfulness-based techniques can be clinically useful in the context of physiotherapeutic multicomponent treatment programs. Trial registration number: NCT04571528

Disentangling Epitaxial Growth Mechanisms of Solution Derived Functional Oxide Thin Films

Altres ajuts: CSIC E-08-2012-1321248 i E-08-2013-1028356This study investigates the mechanisms of epitaxial development and functional properties of oxide thin films (CeZrO , LaNiO, and BaSrTiO) grown on single crystal substrates (YO:ZrO, LaAlO, and SrTiO) by the chemical solution deposition approach. Rapid thermal annealing furnaces are very powerful tools in this study providing valuable information of the early stages of nucleation, the kinetics of epitaxial film growth, and the coarsening of nanocrystalline phases. Advanced transmission electron microscopies, X-ray diffraction, and atomic force microscopy are employed to investigate the film microstructure and morphology, microstrain relaxation, and epitaxial crystallization. This study demonstrates that the isothermal evolution toward epitaxial film growth follows a self-limited process driven by atomic diffusion, and surface and interface energy minimization. All investigated oxides experience a transformation from the polycrystalline to the epitaxial phase. This study unequivocally evidences that the film thickness highly influences the epitaxial crystallization rate due to the competition between heterogeneous and homogeneous nucleation barriers and the fast coarsening of polycrystalline grains as compared to epitaxial growth. The investigated films possess good functional properties, and this study successfully confirms an improvement at long annealing times that can be correlated with grain boundary healing processes. Thick epitaxial films can be crystallized by growing sequential individual epitaxial layers

Electrospun BiFeO3 Nanofibers for Vibrational Energy Harvesting Application

Bismuth ferrite (BiFeO3, BFO) has found application in a wide range of fields owing to its fascinating multiferroic properties. Herein, the interplay between the piezoelectric properties and morphology of BFO nanostructures is exploited for vibrational energy harvesting application by tailoring BFO to a high aspect ratio and high surface area nanofiber morphology. This work demonstrates a facile pathway for the fabrication of high-performance flexible nanogenerators, based on BFO nanofibers, from a cost-effective and energy-efficient electrospinning technique. The X-ray diffraction data of calcined fibers confirm the formation of noncentrosymmetric crystalline perovskite phase. The morphological characterization by scanning electron microscopy shows a compact anisotropic nanofibrous morphology. For the fabrication of nanogenerators, BFO nanofibers are embedded in a piezoactive polymer matrix (polyvinylidenfluoride [PVDF]). As-fabricated BFO/PVDF composite nanogenerators produce a high peak-to-peak voltage output of 7.6 V, with an average output power density of 185 ± 106 nW cm−2 upon periodic application of force through finger knocking.The authors gratefully acknowledge thefinancial support by the EuropeanUnion’s Horizon 2020 research and innovation program (ITN ENHANCE)under the Marie Sklodowska-Curie grant (ID: 722496). The authors arealso grateful to the University of Cologne for providing excellent infrastruc-ture. A.Q. and R.S. thank the Alexander von Humboldt Foundation and theGerman Federal Ministry of Education and Research (BMBF) for thefinan-cial support.Open access funding enabled and organized by Projekt DEALPeer reviewe