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Tensiled La0.5Sr0.5CoO3 (LSCO) thin films were epitaxially grown on piezoelectric 0.67Pb (Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT) single-crystal substrates. Due to the epitaxial nature of the interface, the lattice strain induced by ferroelectric poling or the converse piezoelectric effect in the PMN-PT substrate is effectively transferred to the LSCO film and thus reduces the tensile strain of the film, giving rise to a decrease in the resistivity of the LSCO film. We discuss these strain effects within the framework of the spin state transition of Co3+ ions and modification of the electronic bandwidth that is relevant to the induced strain. By simultaneously measuring the strain and the resistivity, quantitative relationship between the resistivity and the strain was established for the LSCO film. Both theoretical calculation and experimental results demonstrate that the ferroelectric field effect at room temperature in the LSCO/PMN-PT field-effect transistor is minor and could be neglected. Nevertheless, with decreasing temperature, the ferroelectric field effect competes with the strain effect and plays a more and more important role in influencing the electronic transport properties of the LSCO film, which we interpreted as due to the localization of charge carriers at low temperature. [ABSTRACT FROM AUTHOR]

Orientational engineered (La, Mn) co-substituted BiFeO3 (LMBFO) thin films were epitaxially grown on CaRuO3 electroded (LaAlO3)0.3(Sr2AlTaO6)0.35 (LSAT) single crystal substrates by pulsed laser deposition. The experimental results demonstrate that the crystallographic orientation is the critical dominant of the structural and multiferroic properties of LMBFO thin films. Giant remanent polarization of 65, 92, and 106 μC/cm2 for [001], [110], [111]-oriented films, respectively, were demonstrated at room temperature. Saturated magnetization is also significantly dependent on film orientation with the highest value of 12.8 emu/cm3 along [001] direction. The variation in leakage current density and ferroelectric coercivity were ascribed to the substantially difference of ferroelectric domain structures in variously oriented LMBFO thin films. [ABSTRACT FROM AUTHOR]

We have investigated the effects of the strain induced by ferroelectric poling on the transport and magnetic properties of La7/8Ba1/8MnO3 (LBMO) thin films epitaxially grown on ferroelectric 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 (PMN–PT) single-crystal substrates. The ferroelectric poling reduces the in-plane tensile strain of the film, giving rise to a decrease in the resistivity and an increase in the magnetization, Curie temperature, and magnetoresistance of the LBMO film. These strain effects are explained within the framework of coexisting phases whose volume fractions are modified as a result of the reduction in the tetragonal distortion of MnO6 octahedra induced by ferroelectric poling. An investigation of the effects of polarization reversal on the transport properties of the LBMO film indicates that the ferroelectric-poling-induced strain effects dominate over the ferroelectric field effects in the LBMO/PMN–PT structure. [ABSTRACT FROM AUTHOR]

SrRuO3 (SRO) acts as an effective buffer layer for growth of multiferroic BiFeO3 (BFO) thin films deposited on Pt/TiO2/SiO2/Si substrates by radio frequency sputtering. Phase identification by using x-ray diffraction and texture studies by using atomic force microscopy show that the SRO buffer layer promotes crystallization and formation of the perovskite phase at lowered temperature. It significantly reduces the leakage current of multiferroic BFO films, giving rise to a much improved square ferroelectric hysteresis loop, in contrast to the poor loop for BFO on bare Pt/TiO2/SiO2/Si substrate. A much enlarged remnant polarization (2Pr) of 144 μC/cm2 and a coercive field (Ec) of 386 kV/cm were obtained with the BFO thin film deposited on SRO/Pt/TiO2/SiO2/Si at 600 °C. The BFO thin film with SRO buffer layer also shows a large nonvolatile polarization (ΔP=Psw-Pnsw) of 122 μC/cm2 at 20 μs, which promises excellent performance for random access memories. Further interestingly, it exhibits little polarization fatigue up to 5×1010 switching cycles, at a relatively high voltage of 10 V, although a notable degradation of polarization is shown at the low voltage of 6 V, indicating weak domain pinning. The multiferroic thin film demonstrates a weak ferromagnetic loop with a saturation magnetization (Ms) of 1.92 emu/cm3 and coercivity (Hc) of 325 Oe. [ABSTRACT FROM AUTHOR]

Barium zirconate titanate Ba(Zr0.2Ti0.8)O3 (BZT) thin films on La0.7Sr0.3MnO3 (LSMO)-coated Si and Pt/Ti/SiO2/Si substrates have been prepared by pulsed laser deposition and crystallized in situ at 650 °C. Four capacitor types of LSMO/BZT/LSMO/Si, Pt/BZT/LSMO/Si, Pt/BZT/Pt/Si, and Pt/BZT/LSMO/Pt/Si were prepared to investigate the structural and dielectric properties, tunability, and figure of merits. Among them, the high (100)-oriented BZT films were grown on the (100)-textured LSMO and (111)-textured Pt electrodes. The results show that the LSMO/BZT/LSMO/Si has the highest dielectric constant of 555 and Pt/BZT/LSMO/Pt/Si has the highest tunability of 73% at 1 MHz. The high dielectric constant and tunability have been attributed to the (100) texture of the LSMO bottom layer leading to the decrease of the thickness of the interface of the dead layer. [ABSTRACT FROM AUTHOR]

Thin films of La0.7Sr0.3MnO3 (LSMO) have been grown on the ferroelectric 0.68Pb(Mg1/3Nb2/3)O3–0.32PbTiO3 (PMN-PT) single-crystal substrates. The ferroelectric polarization of the PMN-PT induces a large decrease in the resistivity and an upward shift in the Curie temperature of the LSMO films, which was interpreted in terms of the ferroelectric polarization induced large reduction of the biaxial tensile strain in the LSMO films. The resistivity of the LSMO films can be dynamically tuned by applying dc electric fields across the polarized PMN-PT. The analyses of the results indicate that the electric field induced lattice strain via converse piezoelectric effect in the PMN-PT controls the strain states and hence the resistivity and Curie temperature of the LSMO films. [ABSTRACT FROM AUTHOR]

Ferroelectric and dielectric characteristics of Bi1-xLaxFeO3 thin films deposited on SrRuO3 as bottom electrode have been investigated. In accordance with the Rayleigh model, it is in principle established that La doping in BiFeO3 effectively reduces the concentration of charged defects and dielectric loss, although there is a slight deviation at the high level of La doping (x=0.2). This departure is attributed to the reversible bending movement of pinned 180° domain walls, which contributes to the dielectric permittivity nonlinearly without inducing loss. In addition, the competition between domain wall pinning and depinning is determined to be the dominant fatigue mechanism, as shown by the enhanced fatigue endurance at the high La-doping level, test frequency, and electrical field. [ABSTRACT FROM AUTHOR]

Amorphous FexGe1-x films with different metal volume fractions (0.40

[Fe1-δ(FeO)δ]x(TiO2)1-x (0≤δ≤0.91, 0.34≤x≤0.54) granular films were fabricated by magnetron sputtering. Large coercivity (HC = 10.5 kOe) and exchange-bias-field (HE = 6.5 kOe) at 5 K were found in the film with δ=0.84 and x = 0.48. AC susceptibility measurements exhibit a frequency (f) dependent peak Tf in the in-phase susceptibility curve. The fitting of the relation of Tf vs f with both the Vogel-Fulcher law and critical slowing down theory indicate that the evident enhancement of the HC and HE can be qualitatively ascribed to the existence of cluster-spin glass state. The results may help to deeply understand the origin of exchange bias and related effects. [ABSTRACT FROM AUTHOR]

Crystallization, surface morphology, and electrical behavior of BiFeO3 thin films are improved by SrRuO3 (SRO) buffer layer with optimized grain size. Large-grained SRO buffer layer promotes the growth of dense multiferroic BiFeO3 (BFO) thin films and reduces structural defects. Phase identification by using X-ray diffraction and surface morphology studies by using scanning electron microscopy show that the large-grained SRO buffer layer formed by sputtering thicker SRO films promotes the formation of the perovskite phase as well as the crystallinity. These BFO films have also shown reduced leakage current, as suggested by the weaker frequency dependence of the ferroelectric hysteresis loops as compared with the BFO films deposited on smaller-grained SRO buffer layer. Investigation into the dielectric properties and fatigue endurance reveals that the structural defects of the BFO thin film have also been reduced by employing the larger-grained SRO buffer layer. [ABSTRACT FROM AUTHOR]

We have examined the effects of converse piezoelectric effect induced lattice strains on the resistance of the La0.7Sr0.3MnO3 (LSMO) thin films grown on (001)-oriented (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (x∼0.3) (PMN-PT) single-crystal substrates. It has been found that the resistance of the LSMO films can be modulated by the converse piezoelectric effect of the PMN-PT substrates. Piezoelectric displacement measurements indicate that the converse piezoelectric effect induces lattice displacements in the PMN-PT substrates, which modulates the lattice strain and resistance of the LSMO films. Based on the experimental results, the relationship between the resistance of the LSMO films and the converse piezoelectric effect induced lattice strains in the PMN-PT substrates has been discussed. [ABSTRACT FROM AUTHOR]

Ba0.7Sr0.3TiO3 (BST) thin films have been deposited onto (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) single-crystal substrates by pulsed laser ablation. X-ray diffraction revealed that the BST thin films were well crystallized and epitaxially grown on the substrates with a distorted crystal structure comparing with the cubic structure of the BST ceramics. Both the in-plane dielectric constant and tunability of the thin films were found to be dependent on frequency. With increasing frequency from 50 MHz to 10 GHz, the dielectric constant under zero bias field decreases from 1072 to 645, meanwhile, the dielectric tunability under a bias field of 13.3 V/μm decreases from 33% to 20%. The results suggest that the BST films grown on the LSAT substrates are good candidates for composing tunable microwave devices. [ABSTRACT FROM AUTHOR]

Emission of mixtures of organic compounds in thin acrylic films and matrices is investigated from the blue to red range of the spectrum. The present paper is aimed at studying the feasibility of obtaining white light by conversion of output diode radiation (379 nm) using a mixture of fluorophors. It is demonstrated that the emission band shape depends on ratios of dye concentrations and geometry of excitation and registration that must be taken into account in the development of devices based on these compounds. [ABSTRACT FROM AUTHOR]

At room temperature, polycrystalline Fe3O4 films with thicknesses in the range 5–1120 nm have been prepared by reactive sputtering. Transmission electron microscopy imaging shows that uniform Fe3O4 grains are well separated by grain boundaries and their size decreases with film thickness. The change of resistivity as a function of temperature reveals a grain boundary dominated electron tunnelling mechanism. The magnetoresistance MR = (ρH - ρ0)/ρ0 measured at room temperature for the films thicker than 200 nm is ~-7.4% under a magnetic field of 46 kOe, which is among the largest values ever reported for Fe3O4 films under the same measuring conditions. As the thickness reduces from 80 to 5 nm, MR decreases from -6.5% to -1.1% due to the enhanced spin-flip scattering at film and grain surfaces. [ABSTRACT FROM AUTHOR]

The authors report the electronic transport and magnetic properties of the La0.8Ce0.2MnO3 (LCEMO) thin film epitaxially grown on the ferroelectric 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT) single-crystal substrate and their dependence on the polarization state of the PMN-PT substrate. Upon electric-field-induced polarization switching, the electrical resistance and magnetization of the LCEMO film were modulated reversibly. The underlying coupling mechanism that is responsible for the electric-field-control of the resistance and magnetization strongly depends on temperature, being strain-mediated type at relatively high temperatures but becoming charge-mediated type with decreasing temperature. The knowledge about the evolution of the coupling mechanism with temperature not only helps to understand the drive force for multiferroic properties but also is important for theoretical modeling and device fabrication. [ABSTRACT FROM AUTHOR]

The authors have studied the substrate-induced strain effect in La0.875Ba0.125MnO3 (LBMO) thin films grown on ferroelectric 0.67Pb(Mg1/3Nb2/3)O3–0.33PbTiO3 (PMN-PT) single-crystal substrates. Both the strain and resistance of the films can be in situ varied by applying an electric field across the PMN-PT substrates. X-ray diffraction analysis indicates that the variations of strain and resistance result from the induced strain in the PMN-PT substrate due to the ferroelectric polarization or the converse piezoelectric effect. The relationships between the resistance and the induced strain in the LBMO film and PMN-PT substrate have been quantitatively analyzed. [ABSTRACT FROM AUTHOR]

The authors have deposited thin films of La0.85Sr0.15MnO3 (LSMO) on 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN-PT) single-crystal substrates and have achieved modulation of the resistance of the LSMO film by applying an electric field across the PMN-PT substrate whether the LSMO film is in the paramagnetic, ferromagnetic, or charge-ordered state. Piezoelectric measurements show that the electric field gives rise to a lattice strain in the PMN-PT substrate via the converse piezoelectric effect, which then induces a lattice strain and hence a resistance change in the LSMO film. Analysis of the data indicates that the electric-field-induced lattice strain effect dominates over the field effect in the LSMO/PMN-PT structure. [ABSTRACT FROM AUTHOR]

The authors have studied the effects of film thickness on the lattice strain and in-plane dielectric and ferroelectric properties of Ba0.7Sr0.3TiO3 thin films epitaxially grown on LaAlO3 (001) single crystal substrates. With increasing film thickness from 20 to 300 nm, the in-plane lattice parameter (a) increased from 0.395 to 0.402 nm while the out-of-plane lattice parameter (c) remained almost unchanged, which led to an increased a/c ratio (tetragonality) changing from 0.998 to 1.012 and consequently resulted in a shift of Curie temperature from 306 to 360 K associated with an increase of the in-plane remnant polarization and dielectric constant of the film. [ABSTRACT FROM AUTHOR]

The microstructure and in-plane dielectric and ferroelectric properties of highly oriented Ba0.7Sr0.3TiO3 (BST) thin film grown on MgAl2O4 (001) single-crystal substrate through pulsed laser deposition were investigated. X-ray diffraction measurements indicated that BST had a distorted lattice with a tetragonality a/c=1.012. The cross-sectional observation under transmission electron microscope revealed that, while most of BST grains grew epitaxially on MgAl2O4, the film also contained a noticeable amount of misoriented grains and dislocations. The electrical measurements indicated that the film had a shifted Curie temperature (TC=78 °C) and an enhanced in-plane ferroelectricity (remnant polarization Pr=7.1 μC/cm2) when compared with BST ceramic (TC≈33 °C and Pr≈0). [ABSTRACT FROM AUTHOR]

The effects of ferroelectric-poling-induced strain on the transport and magnetic properties of the phase separated La1/8Pr4/8Ca3/8MnO3 (LPCMO) thin films epitaxially grown on the ferroelectric 0.67Pb(Mg1/3Nb2/3)O3-0.33PbTiO3 (PMN-PT) single-crystal substrates were investigated. The ferroelectric poling reduces the in-plane tensile strain and enhances the out-of plane tensile strain of LPCMO film, which decreases the resistance and the charge ordering transition temperature but raises the low-field-magnetization of film. These results can be explained by the strain induced change in the volume fraction of coexisting phases, i.e., ferromagnetic, antiferromagnetic, and paramagnetic phases, demonstrating that the charge ordering phase transition of manganites film grown on the ferroelectric PMN-PT substrate can be controlled by modifying the poling state of single crystal substrate. [ABSTRACT FROM AUTHOR]

Apart from the scientific interest, texture development in copper thin films is of crucial importance to their applications as interconnects or corrosion resistant coating. We report here a dominant 〈110〉 texture of copper thin films—preferred for oxidation-resistant applications—deposited by direct current magnetron sputtering. Scanning electron microscopy shows that the copper films go through a transition from 〈111〉 columns to 〈110〉 hillocks as the deposition proceeds. Cross-sectional transmission electron microscopy (TEM) indicates that the 〈110〉 grains nucleate at boundaries of 〈111〉 grains. Further, we have proposed a stress-driven nucleation and growth model of 〈110〉 grains based on the x-ray diffraction characterization and the TEM observations. [ABSTRACT FROM AUTHOR]

The authors have studied the effects of film thickness on the lattice strain and in-plane dielectric and ferroelectric properties of Ba0.7Sr0.3TiO3 thin films epitaxially grown on LaAlO3 (001) single crystal substrates. With increasing film thickness from 20 to 300 nm, the in-plane lattice parameter (a) increased from 0.395 to 0.402 nm while the out-of-plane lattice parameter (c) remained almost unchanged, which led to an increased a/c ratio (tetragonality) changing from 0.998 to 1.012 and consequently resulted in a shift of Curie temperature from 306 to 360 K associated with an increase of the in-plane remnant polarization and dielectric constant of the film. [ABSTRACT FROM AUTHOR]