Growth of epitaxial CeO 2 buffer layers by polymer assisted deposition
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Growth of epitaxial CeO2 buffer layers by polymer assisted deposition A. Calleja1, R. B. Mos1,2, P. Roura3, J. Farjas3, J. Arbiol1,4, L. Ciontea2, X. Obradors1, T. Puig1 1
Institut de Ciència de Materials de Barcelona-Consejo Superior de Investigaciones Científicas (ICMAB-CSIC), Bellaterra, Catalonia, Spain 2
3
Technical University of Cluj, Cluj-Napoca, Romania
GRMT, Dept. of Physics, University of Girona, Campus Montilivi, Edif. PII, E17071 Girona, Catalonia, Spain 4
Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010, Barcelona, Catalonia, Spain
ABSTRACT Polymer assisted deposition (PAD) has been reported as a novel CSD approach for thin film growth with improved homogeneity and long stability by forming a metal polymer species. It also offers the interesting possibility of having a library of PAD solutions for each precursor metal and obtaining the required composition by simple mixing. Another potential advantage is the increase in thickness since mechanical stresses are expected to be alleviated during shrinkage in the metalorganic decomposition by the metal-polymer network. Cerium oxide films on YSZ single crystals were grown from water-based solutions containing cerium nitrate, polyethyleneimine and complexing EDTA, in order to explore the benefits of using the PAD approach for growing buffer layers in coated conductors. An ultrafiltration step was performed to remove the non-coordinated species in solution. The degree of purification and efficiency in the cerium recovery was investigated by different techniques. TGA-DTA analysis was used to provide guidance to the best thermal profiles in different atmospheres and specially to diminish the adverse effects of exothermic events during decomposition. Microstructural evolution was tracked by AFM and TEM, while epitaxial fraction was followed by X-ray diffraction. The results show the high importance of choosing the proper atmosphere and the need for tuning of heating ramps to obtain dense, flat and epitaxial ceria films by PAD.
INTRODUCTION Ceria (CeO2) is an important component in many technological devices due to its remarkable properties [1]. Most of the technological applications envisage its use in catalysis [2], electrochemistry [3] and optics [4]. Lately, the cerium oxide (CeO2) thin films have been widely used in the fabrication of coated conductors as a promising buffer layer due to the good chemical
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compatibility and lattice match with YBa2Cu3O7 (YBCO) (İ = -0.5 %). There is a clear need for full understanding of surface chemistry and morphology of CeO2 thin films on the properties of the final superconducting film. Compared with the vacuum deposition methods, chemical solution deposition [5-7] requires less equipment and less complexity for upscaling. Recently, Q.X. Jia et al. [8] have reported a general methodology for the epitaxial growth of thin films on single crystalline substrates using inorganic salts as precursors obtained by a new chemical method called Polymer Assisted Deposition (PAD). In the PAD process, an aqueou
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