Relevance of the Formation of Intermediate Non-Equilibrium Phases in YBa2Cu3O7-x Film Growth by Transient Liquid-Assisted Growth

Transient liquid-assisted growth (TLAG) is a non-equilibrium ultrafast method to grow YBa2Cu3O7–x (YBCO) superconducting films at up to 100 nm/s using chemical solution deposition. In this work, we study the formation of non-equilibrium crystalline intermediate phases prior to the growth of YBCO through TLAG. We analyze the thermal decomposition and microstructural evolution of a propionate-based fluorine-free solution used as precursor to YBCO epitaxial films. Thermal analyses (TGA, DSC), coupled with techniques to monitor the volatiles (TG-IR), were applied in situ during film pyrolysis in humid O2, while the thermal evolution of the solid residue was characterized by infrared spectroscopy and X-ray diffraction, both ex situ and in situ in synchrotron radiation sources, and by scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) cross-sectional analysis. Unexpected effects, observed during the decomposition of the ternary solution, are the formation of intermediate non-equilibrium phases: Cu2O or Cu(0) and monoclinic BaCO3. We emphasize that working with anhydrous solutions and anhydrous deposition conditions promotes the formation of the expected equilibrium phases. Finally, in situ X-ray diffraction permits monitoring the influence of the non-equilibrium monoclinic BaCO3 phase on the formation of binary oxide phases, precursors of TLAG YBCO film growth. Understanding the evolution of non-equilibrium phases is shown to be fundamental for the control of the final YBCO film’s microstructure and performance, since the latter are strongly affected by the film’s thermal history after solution deposition.This work was funded by Ministerio de Ciencia, Innovation y Universidades (RTI2018-095853-B-C21 and RTI2018-095853-B-C22) cofinanced by the European Regional Development Fund, and the EU Ultrasupertape project (ERC ADG-2014-669504). We also acknowledge the Center of Excellence Severo Ochoa (SEV-2015-0496), the Generalitat de Catalunya (2017-SGR-1519) and the COST -action NANOCOHYBRI (CA16218). In situ FTIR experiments were performed at the MIRAS beamline of the ALBA Synchrotron with the collaboration of ALBA staff. We also thank the DiffAbs beamline at SOLEIL Synchrotron facility and the beamline staff support for the in situ XRD experiments. We thank the ICMAB, INA-Zaragoza and UdG scientific services and technical staff for the support on the experiments. S.R. thanks the Universitat de Girona (UdG) for the IFUdG grant. L.S. and J.J. also acknowledge their FPU-MINECO PhD grant.Peer reviewe

Kinetic Control of Ultrafast Transient Liquid Assisted Growth of Solution-Derived YBa2Cu3O7-x Superconducting Films

Transient liquid assisted growth (TLAG) is an ultrafast non-equilibrium growth process mainly governed by kinetic parameters, which are only accessible through fast in situ characterizations. In situ synchrotron X-ray diffraction (XRD) analysis and in situ electrical resistivity measurements are used to derive kinetic diagrams of YBa2 Cu3 O7- x (YBCO) superconducting films prepared via TLAG and to reveal the unique peculiarities of the process. In particular, diagrams for the phase evolution and the YBCO growth rates have been built for the two TLAG routes. It is shown that TLAG transient liquids can be obtained upon the melting of two barium cuprate phases (and not just one), differentiated by their copper oxidation state. This knowledge serves as a guide to determine the processing conditions to reach high performance films at high growth rates. With proper control of these kinetic parameters, films with critical current densities of 2-2.6 MA cm-2 at 77 K and growth rates between 100-2000 nm s-1 are reached. These growth rates are 1.5-3 orders of magnitude higher than those of conventional methods.The authors acknowledge the European Research Council for the ULTRASUPERTAPE project (ERC-2014-ADG-669504), IMPACT project (ERC-2019-PoC-874964) and EU COST action for CA16218 (NANOCOHYBRI). The authors also acknowledge financial support from Spanish Ministry of Science and Innovation with PID2021-127297OB-C21 and PID2021-127297OB-C22, and from Spanish Ministry of Science, Innovation and Universities through the “Severo Ochoa” Program for Centers of Excellence in R&D (SEV-2015-0496 and CEX2019-000917-S), and from the Spanish Ministry of Economy and Competitiveness with the SUMATE project (RTI2018-095853-B-C21, RTI2018-095853-B-C22, co-financed by the European Regional Development Fund, MCIU/AEI/FEDER, UE). They also thank the Catalan Government (2017-SGR-1519) and the Catalan energy network XRE4S (2018 XARDI 00002) for their support. L.S., D.G., and A.K. acknowledge financial support from Spanish Ministry of Science, Innovation and Universities through the FPI grant PRE2019-090621, PRE2018-084537, and PRE2020-091817, respectively. L.So. and J.J. acknowledge financial support from Spanish Ministry for the FPU grants. S.R. thanks the Universitat de Girona for IFUdG grant and A.Q. thanks the Spanish Ministry of Science, Innovation and Universities (“Juan de la Cierva” postdoctoral fellowship [Grant no. IJC2018-035034-I]). The authors thank the Scientific Services at ICMAB and ICN2 Electron Microscopy Division. The authors acknowledge the use of instrumentation as well as the technical advice provided by the National Facility ELECMI ICTS, node “Laboratorio de Microscopías Avanzadas” at University of Zaragoza. The authors also acknowledge SOLEIL Synchrotron for provision of synchrotron radiation facilities and are grateful for assistance while using the DiffAbs beamline.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

Defect landscape and electrical properties in solution-derived LaNiO3 and NdNiO3 epitaxial thin films

In this work we evaluate the defects and the associated distortions present in tensile and compressive-strained chemical solution deposition (CSD) derived NdNiO3 (NNO) and LaNiO3 (LNO) thin-films by means of aberration corrected Scanning Transmission Electron Microscopy (STEM). We elucidate a fundamental link between strain and the most common defect observed in Nickelate films, the Ruddlesden-Popper fault (RPF), which will ultimately impinge on the electrical properties of the films. Overall, the concentration of RPFs defects increases with the lattice mismatch. More specifically, LNO films are always metallic, although transitioning from compressive to tensile strain results in the appearance of RPFs and an increase of the resistivity. On the other hand, NNO films always behave as insulators under tensile strain, whereas under compressive strain the increase of the thickness makes the onset of the metal-to-insulator transition (MIT) to shift to higher temperatures.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 (MAT2014-51778-C2-1-R and BES-2015-072749 grant for B.M, co-financed by the European Regional Development Fund) and from the Catalan Government with 2017 SGR 1519 and Xarmae. J.J. acknowledges an FPU grant (FPU14/05960) from Ministerio español de Educación, Cultura y Deporte para la Formación de Profesorado Universitario and J.G. acknowledges the Ramon y Cajal program (RyC-2012–11709). The STEM microscopy work was conducted in the ICTS-CNME at UCM as well as at the Laboratorio de Microscopias Avanzadas (LMA) at Instituto de Nanociencia de Aragon (INA) at the University of Zaragoza. Authors acknowledge the ICTS-CNME for offering access to their instruments and expertise. Electron microscopy performed at the Centro Nacional de Microscopía Electrónica (UCM) were sponsored by the ERC Starting Investigator Award No. STEMOX#239739.Peer reviewe

Ultrafast transient liquid assisted growth of high current density superconducting films

The achievement of high growth rates in YBa2Cu3O7 epitaxial high-temperature superconducting films has become strategic to enable high-throughput manufacturing of long length coated conductors for energy and large magnet applications. We report on a transient liquid assisted growth process capable of achieving ultrafast growth rates (100 nm s−1) and high critical current densities (5 MA cm−2 at 77 K). This is based on the kinetic preference of Ba-Cu-O to form transient liquids prior to crystalline thermodynamic equilibrium phases, and as such is a non-equilibrium approach. The transient liquid-assisted growth process is combined with chemical solution deposition, proposing a scalable method for superconducting tapes manufacturing. Additionally, using colloidal solutions, the growth process is extended towards fabrication of nanocomposite films for enhanced superconducting properties at high magnetic fields. Fast acquisition in situ synchrotron X-ray diffraction and high resolution scanning transmission electron microscopy (STEM) become crucial measurements in disentangling key aspects of the growth process.Authors acknowledge EU for ULTRASUPERTAPE ERC-2014-ADG-669504; COACHSUPENERGY MAT2014-51778-C2-1-R and MAT2014-51778-C2-2-R from MINECO; SuMaTe RTI2018-095853-B-C21 and RTI2018-095853-B-C22 from MICINN and co-financing by the European Regional Development Fund; 2017-SGR 1519 from Generalitat de Catalunya; and EU COST Action NANOCOHYBRI (CA16218). ICMAB authors acknowledge the Center of Excellence award Severo Ochoa SEV-2015-0496. Authors thank Dr. Cornelia Pop, Dr. Bohores Villarejo, Dr. Bernat Mundet, and Dr Anna Palau for contributions at the initial stages of the project. We thank Diana García, Lavinia Saltarelli, Adria Pacheco, Dr. Max Sieger, and Dr. Albert Queralto for help in the feasibility study and preliminary results on thick films and coated conductors. Authors acknowledge support from SuNAM Co Ltd. for providing the buffered metallic substrates for the initial tests on coated conductors. We also acknowledge the Scientific Services at ICMAB, ICTS of IMB-CNM-CSIC, ICN2 Electron Microscopy Division and LMA-INA from Aragon, and SOLEIL Synchrotron for granting beamtime for XRD experiments and the DiffAbs beamline personnel for help. L.S. and J.J. also acknowledge their FPU-MINECO PhD grant, S.R. and N.C. thank University of Girona and Generalitat de Catalunya fort their PhD FI grant, respectively.Peer reviewe

Volume Resistive Switching in metallic perovskite oxides driven by the Metal-Insulator Transition

In recent years Resistive Random Access Memory (RRAM) is emerging as the most promising candidate to substitute the present Flash Technology in the non-volatile memory market. RRAM are based on the Resistive Switching (RS) effect, where a change in the resistance of the material can be reversibly induced upon the application of an electric field. In this sense, strongly correlated complex oxides present unique intrinsic properties and extreme sensitivity to external perturbations, which make them suitable for the nanoelectronics of the future. In particular, metallic complex oxides displaying metal-insulator transition (MIT) are very attractive materials for applications and are barely explored as RS active elements. In this work, we analyze the RS behavior of three different families of metallic perovskites: La0.8Sr0.2MnO3, YBa2Cu3O7-δ and NdNiO3. We demonstrate that these mixed electronic-ionic conductors undergo a metal-insulator transition upon the application of an electric field, being able to transform the bulk volume. This volume RS is different in nature from interfacial or filamentary type and opens new possibilities of robust device design. As an example, we present a proof-of-principle result from a 3-Terminal configuration with multilevel memory states.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), OXSWITCH project funded by Centro Superior de Investigaciones Científicas (CSIC) and from the Catalan Government with 2014-SGR-753 and Xarmae. We also acknowledge Dr. Jaume Gazquez and Mr. Bernat Munder for the TEM images. J.C.G.R. thanks Spanish Ministry of Economy for his FPI Spanish grant (BES-2012-053814). R.O. thanks Generalitat de Catalunya for the Grant through AGAUR FI-DGR program. JS acknowledges the support of the Generalitat de Catalunya under the ICREA ACADEMIA award.Peer reviewe