The influence of A-site rare-earth for barium substitution on the chemical structure and ferroelectric properties of BZT thin films |
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Authors: | C Ostos ML Martínez-Sarrión E Delgado |
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Institution: | a Department of Inorganic Chemistry, University of Barcelona, C/Martí i Franquès, 1-11, 08028 Barcelona, Spain b Center of Nanoscience and Nanotechnology, UNAM, A. Postal 2681, 22800 Ensenada B.C, Mexico c Department of Physics, Universidad del Valle, Building 320-3001, Cali, Colombia d Center of Excellence on Novel Materials, Universidad del Valle, A.A. 25360, Cali, Colombia |
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Abstract: | Rare-earth (RE) doped Ba(Zr,Ti)O3 (BZT) thin films were prepared by rf-magnetron sputtering from a Ba0.90Ln0.067Zr0.09Ti0.91O3 (Ln=La, Nd) target. The films were deposited at a substrate temperature of 600 °C in a high oxygen pressure atmosphere. X-ray diffraction (XRD) patterns of RE-BZT films revealed a 〈001〉 epitaxial crystal growth on Nb-doped SrTiO3, 〈001〉 and 〈011〉 growth on single-crystal Si, and a 〈111〉-preferred orientation on Pt-coated Si substrates. Scanning electron microscopy (SEM) showed uniform growth of the films deposited, along with the presence of crystals of about half-micron size on the film's surface. Transmission electron microscopy (TEM) evidenced high crystalline films with thicknesses of about 100 nm for 30 min of sputtering. Electron-probe microanalysis (EPMA) corroborated the growth rate (3.0-3.5 nm/min) of films deposited on Pt-coated Si substrates. X-ray photoelectron spectroscopy (XPS), in depth profile mode, showed variations in photoelectron Ti 2p doublet positions at lower energies with spin-orbital distances characteristic of BaTiO3-based compounds. The XPS analysis revealed that lanthanide ions positioned onto the A-site of the BZT-perovskite structure increasing the MO6-octahedra distortion (M=Ti, Zr) and, thereby, modifying the Ti-O binding length. Polarization-electric field hysteresis loops on Ag/RE-doped BZT/Pt capacitor showed good ferroelectric behavior and higher remanent polarization values than corresponding non-doped system. |
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Keywords: | BZT Perovskites Thin films Magnetron sputtering Ferroelectrics |
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