Ferroelectric and structural instability of (Pb,Ca)TiO3 thin films prepared in an oxygen atmosphere and deposited on LSCO thin films which act as a buffer layer |
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Authors: | D.S.L. Pontes F.M. Pontes Marcelo A. Pereira-da-Silva M. Zampieri A.J. Chiquito P.S. Pizani E. Longo |
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Affiliation: | 1. LIEC – Department of Chemistry, Universidade Federal de São Carlos, Via Washington Luiz, Km 235, P.O. Box 676, 13565-905 São Carlos, São Paulo, Brazil;2. Department of Chemistry, Universidade Estadual Paulista – Unesp, P.O. Box 473, 17033-360 Bauru, São Paulo, Brazil;3. Institute of Physics of São Carlos, USP, São Carlos 13560-250, São Paulo, Brazil;4. NanoLab – Department of Physics, Universidade Federal de São Carlos, Via Washington Luiz, Km 235, P.O. Box 676, 13565-905 São Carlos, São Paulo, Brazil;5. Department of Physics, UFSCar, Via Washington Luiz, Km 235, CEP-13565-905 São Carlos, São Paulo, Brazil;6. Institute of Chemistry, Universidade Estadual Paulista – Unesp, Araraquara, São Paulo, Brazil |
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Abstract: | Structural, microstructural and ferroelectric properties of Pb0.90Ca0.10TiO3 (PCT10) thin films deposited using La0.50Sr0.50CoO3 (LSCO) thin films which serve only as a buffer layer were compared with properties of the thin films grown using a platinum-coated silicon substrate. LSCO and PCT10 thin films were grown using the chemical solution deposition method and heat-treated in an oxygen atmosphere at 700 °C and 650 °C in a tube oven, respectively. X-ray diffraction (XRD) and Raman spectroscopy results showed that PCT10 thin films deposited directly on a platinum-coated silicon substrate exhibit a strong tetragonal character while thin films with the LSCO buffer layer displayed a smaller tetragonal character. Surface morphology observations by atomic force microscopy (AFM) revealed that PCT10 thin films with a LSCO buffer layer had a smoother surface and smaller grain size compared with thin films grown on a platinum-coated silicon substrate. Additionally, the capacitance versus voltage curves and hysteresis loop measurement indicated that the degree of polarization decreased for PCT10 thin films on a LSCO buffer layer compared with PCT10 thin films deposited directly on a platinum-coated silicon substrate. This phenomenon can be described as the smaller shift off-center of Ti atoms along the c-direction 〈001〉 inside the TiO6 octahedron unit due to the reduction of lattice parameters. Remnant polarization (Pr) values are about 30 μC/cm2 and 12 μC/cm2 for PCT10/Pt and PCT10/LSCO thin films, respectively. Results showed that the LSCO buffer layer strongly influenced the structural, microstructural and ferroelectric properties of PCT10 thin films. |
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Keywords: | Thin films Buffer layers Pb1&minus xCaxTiO3 Chemical synthesis |
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