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In Ba0.6Sr0.4TiO3 (BSTO)-based epitaxial nanocomposite films increased Pr values are demonstrated by up to a factor of 3 compared to standard BSTO films. A strongly reduced temperature coefficient of polarization retention is also obtained, i.e., 0.07% °C−1 compared to 0.24% °C−1. Piezopoling with only marginal leakage current is also achieved up to 200 °C, the highest temperature studied. The origin of the improved performance is the incorporation of Sm2O3 nanopillars in the films which acted as stiff vertical nanoscaffolds, inducing a strong tetragonal distortion in the BSTO (up to 1.033(7) in terms of the out-of-plane/in-plane lattice dimensions). The films have comparable performance to industry-standard Pb(Zr,Ti)O3 films, at the same time as being Pb-free. [ABSTRACT FROM AUTHOR]

Unimorph cantilevers are made from 0.5BaTiO3-0.5Sm2O3 (BTO-SmO) self-assembled vertical heteroepitaxial nanocomposite thin films, grown by PLD on (001) SrTiO3 single crystal substrates. The films remain piezoelectric up to at least 250 °C without losing any actuation. The longitudinal piezoelectric coefficient, d33, is ≈45 to 50 pm V−1 measured from room temperature to 250 °C. The transverse piezoelectric coefficient, d31, a key parameter of actuator performance, exceeds PZT (Pb1-xZrxTiO3) films at >200 pm V−1. Since the d31 coefficient was found to be positive, this opens up exciting new applications opportunities. The possible reasons for d31 > 0 are discussed in the light of 3D strain control in the nanocomposites. [ABSTRACT FROM AUTHOR]

In this study Te-rich iron chalcogenide (FeSexTe1−x) thin films with a composition close to antiferromagnetic ordering have been deposited on SrTiO3 (STO) substrates. The superconducting critical transition temperature (Tc) of the FeSe0.1Te0.9 thin film on STO substrate ranges from ∼12.5 to ∼13.3 K. The upper critical field is as high as 114 T, which is much higher than that of the FeSe0.5Te0.5 thin film on STO substrate (∼49 T). The self-field critical current density () at 2 K of 1.8 × 105 A cm−2 is much higher than that of the FeSe0.5Te0.5 thin film, and the FeSe0.1Te0.9 thin film also demonstrates superior pinning properties under applied magnetic field. Compared to FeSe0.5Te0.5, which was considered as the optimum composition, FeSe0.1Te0.9 presents even more promise for high field applications because of its high upper critical field and high critical current density. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we report epitaxial tetragonal iron selenide thin films grown on single crystal SrTiO3 (STO) (001) and MgO (001) substrates by a pulsed laser deposition (PLD) technique. Deposition temperature and annealing process are found to be critical for achieving the tetragonal phase and the optimum superconducting properties of the films. The critical transition temperature of the thin films ranges from 2K to 11.5K depending on the deposition temperature and annealing condition. The samples with higher critical transition temperatures show better film crystallinity along with self-assembled Fe3O4 nanoparticles (∼15nm in average particle size) in the films according to both X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. Besides the better crystallinity achieved in the films, the formation of Fe3O4 nanoparticles could assist the formation of the tetragonal FeSe phase and thus lead to the enhanced superconducting properties. [Copyright &y& Elsevier]

YBa2Cu3O7-\delta (YBCO) thin films doped with either secondary nanoparticles or nanolayers have demonstrated enhanced flux pinning properties in applied magnetic field. One possible reason for the enhanced flux pinning properties is the interfacial defects generated at the heterogeneous interfaces between YBCO and nanoparticles/nanolayers. In this work, we conducted a systematic study to correlate the pinning properties of YBCO thin films with interfacial defect density by introducing CeO2 multilayered structures. Multilayered YBCO thin films with 1-, 2-, and 4-CeO2 interlayers and a pure YBCO reference thin film were prepared by pulsed laser deposition through alternating YBCO and CeO2 targets. A detailed microstructure and superconducting property analysis was conducted by X-ray diffraction (XRD), high resolution cross-sectional transmission electron microscopy (TEM), and physical properties measurement system (PPMS) with vibrating sample magnetometer (VSM). The result showed that introducing CeO2 nanolayers can effectively increase the interfacial defects without degrading the epitaxy quality of YBCO films. We found that an optimum density of interfacial defects in YBCO matrix is needed for the enhanced self-field and in-field performance. [ABSTRACT FROM AUTHOR]

ZnO and Ag-doped ZnO films were grown on sapphire (0001) substrates by pulsed-laser deposition in vacuum both with and without oxygen at 700 °C. N+ ions were implanted in these films at room temperature and at 300 °C to a dose of 1×1014 cm-2 at 50 keV. Hall measurements indicate that ZnO films deposited in vacuum without oxygen and implanted with N+ at elevated temperatures are p-type with a hole-carrier concentration of 6×1016 cm-3, a mobility of 2.1 cm2 V-1 s-1, and a resistivity of 50 Ω cm. Both scanning-electron microscopy and transmission-electron microscopy studies on the implanted films reveal microstructural differences in grain size, surface roughness, and the nature of defects, which may impact the activation of N atoms as p-type carriers. Low-energy ion implantation at elevated temperatures is shown to be an effective method to introduce p-type N dopants into ZnO, which minimizes defect clustering and promotes defect annihilation during implantation. [ABSTRACT FROM AUTHOR]

In this paper, we report a strong enhancement in the in-field transport properties of the YBa2Cu3O7-δ (YBCO) thin films doped with magnetic Fe2O3 nanoparticles. We incorporated magnetic Fe2O3 nanoparticles with two different architectures by laser ablation of the YBCO and dopant targets. YBCO film thickness was controlled at around 1 μm for all the samples. We conducted a detailed microstructural characterization on all the doped samples by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (TEM) and compared with the pure YBCO films. A systematic study on the superconducting properties has been conducted on all the thin film samples. The critical current densities at both self-field and in-field (Jsf and Jin-field (H//c)) and the critical transition temperature (Tc) of the doped and un-doped YBCO sample were measured by a Superconducting Quantum Interference Device (SQUID). The Tc of the doped YBCO films varies from 84 K-.90 K and the Jc is in the range of 1.2-3.9 MA/cm2 (at 65 K) depending on the doping approach. The pinning properties of these doped YBCO films were explored at different temperatures (5 K, 40 K, and 65 K) and correlated with their microstructural characteristics. [ABSTRACT FROM AUTHOR]