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Lead-free BaTiO3 (BTO) film was fabricated by pulsed laser deposition on LaAlO3/SrTiO3 (LAO/STO) heterostructure in oxygen pressure of 2 × 10−3 Pa, which is experimentally required for ensuring the two-dimensional electron gas at LAO/STO heterointerface. Modulation of back-gate voltage on the superconductivity of LAO/STO and BTO/LAO/STO heterointerfaces was studied. The results indicate that the back-gate voltage can adjust the resistance at high temperatures around 300 mK, while it does not modulate the superconducting transition temperature of LAO/STO, which occurs at 160 mK. As for BTO/LAO/STO, it still shows a superconducting transition-like behavior at 110 mK. However, when a negative back-gate voltage is applied, the superconducting transition-like behavior disappears, and after removing the voltage, unlike what was observed for LAO/STO, the superconductivity cannot be recovered. Given this, some underlying mechanisms are proposed. [ABSTRACT FROM AUTHOR]

High permittivity 0.9Pb(Mg1/3Nb2/3)O3-0.1PbTiO3 (PMNT) relaxor thin films with a nearly pure perovskite structure as well as a dense and uniform microstructure have been prepared on Pb(Zr,Ti)O3-buffered platinized silicon substrates by sol-gel method. Interestingly, the PMNT thin film exhibits high dielectric permittivity, [variant_greek_epsilon]r ∼ 1200, and high dielectric tunability, ∼70% under a moderate E = 333 kV/cm, over a wide temperature range. These results are explained in terms of a relaxor behavior of the PMNT film. Moreover, the leakage current density of the PMNT thin film is reasonably low, roughly 5.2 × 10-6 A/cm2 at an electric field intensity of 400 kV/cm. As the dc electric field increases, the leakage current mechanism is transformed from ohmic law to Fowler-Nordheim tunneling mechanism. All the results obtained indicate that the PMNT relaxor thin film is a good candidate for high-value, wide-temperature capacitor applications. [ABSTRACT FROM AUTHOR]

A LaAlO3/SrTiO3 (LAO/STO) heterointerface with the sheet charge density of electrons on the order of magnitude of 1013 e/cm2 was obtained by depositing a 10 unit-cell LAO layer on the TiO2-teminated STO substrate. An obvious persistent photoconductivity effect was observed for the as-prepared LAO/STO heterointerface. By way of Hall-like coefficient and magnetoresistance measurements at different light power intensities, it is demonstrated that the mechanism of magnetoresistance changes with the increase in light power density on the sample; more importantly, when the light power intensity is increased to a specific value, 270 mW in this case, the carrier type of the interface is tailored from n-type to p-type, which is probably ascribed to the photoinduced p-type hole dopants and has never been reported at the LAO/STO interface before, thus providing important insights into a controllable heterointerface for oxide-based thin film electronics. [ABSTRACT FROM AUTHOR]

BaSrTiO (BST), 5 mol% Mn-doped BST (Mn-BST) and bilayered Mn-BST/BST films with a thickness of about 100 nm were fabricated by using pulsed laser deposition technique on MgO single crystal substrates, and their microwave dielectric properties were comparatively investigated. It was confirmed that all the BST-based films were crystallized in pure single-oriented perovskite phase. There appeared nanosized pores in the BST film; after addition of Mn, however, the film surface morphology became denser while exhibiting an increased roughness, and ultimately, a smooth and dense morphology was achieved by the design of bilayered Mn-BST/BST film. Coherently, the microwave dielectric properties of BST films were enhanced by Mn doping and more significantly enhanced in the bilayered Mn-BST/BST film. As a result, for the bilayered film, a very low loss tangent of 0.017-0.007 and a high dielectric tunability of 70.9% under E = 36 V/μm were simultaneously obtained at 79 K and L-band frequency (1-2 GHz), thereby resulting in an extremely high commutation quality factor of 14492. The excellent microwave dielectric properties obtained in the Mn-BST/BST bilayered film originate not only from the Mn-doping effect, but are also ascribed to the pre-deposition of BST layer, which serves as a good template for the growth of Mn-BST film. [ABSTRACT FROM AUTHOR]

Abstract: Multiferroic Bi1− x La x FeO3 (x =0.00, 0.05, 0.10, 0.15, 0.20) (represented as B1− x L x FO) ceramics were prepared using the conventional solid state reaction route. The effects of La3+ doping on the density, phase structure, morphology, dielectric and ferroelectric properties were investigated. Judging from X-ray diffraction patterns, all the B1− x L x FO ceramic samples were well crystallized in a pure perovskite phase while the crystal structure changed from rhombohedral to orthorhombic with increasing the La3+ substitution. SEM observations clearly revealed that the grain size was remarkably decreased by La3+ doping. As a result, the ferroelectric Curie temperature was lowered in the La-doped ceramics. However, the abnormal dielectric responses near the antiferromagnetic Néel temperature (T N) demonstrated the existence of remarkable magnetoelectric coupling in the Bi1 −x La x FeO3 ceramics, and the T N was shown to increase substantially with the increase in La3+ doping content. It was found that the dielectric permittivity of the ceramics was significantly increased and the dielectric loss was slightly increased with the increase in La3+ content. The dielectric constant ε r of the Bi0.85La0.15FeO3 ceramic at 10kHz reached as high as 1008, 20 times larger than that for pure BiFeO3. In addition, the ferroelectric properties of the B1− x L x FO ceramics were improved and the remanent polarization was increased by La3+ doping. This is probably because the A-site doping with more stable La3+ could reduce the volatilization of Bi3+ and, thus, reduce the concentration of charged defects or defect dipole complexes, such as , or in the ceramics. [Copyright &y& Elsevier]