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The interface of a La0.7Sr0.3MnO3/SrTiO3 bilayer was modulated by introducing 3 unit cells of Ba1-xSrxTiO3 using Combinatorial Pulsed Laser Deposition. A wide range of chemical compositions was studied within the same sample, with BSTx stoichiometry variable from 0.5 to 1 along Y-axis, while the SrTiO3 overlayer thickness was modified along the X direction [Fig. 1(a)]. We performed high-resolution, laboratory-based angle-resolved XPS studies of the BSTx film surface providing information on the thickness and composition of the surface and sub-surface layers. Based on the attenuation of the La 3d corelevel photoemission signal from the La0.7Sr0.3MnO3 bottom layer, the BST layer is 1.2 nm thick. XPS Ba 3d5/2 core-level spectra were acquired at positions corresponding to different nominal Ba/Sr stoichiometry. In all measurements, the Ba 3d5/2 core-level spectra can be represented by two main components, i.e. one component at higher binding energy (BE = 780.54 eV) corresponding to surface contribution and the other one at lower binding energy (BE = 778.92 eV) corresponding to sub-surface contribution (Figs. 2 and 3). Going from normal to 60° emission angle and using a 3-unit cell thick film model, the surface to sub-surface intensity ratio clearly evolves providing evidence of a Ba-rich surfactant. The surfactant effect is more significant for lower nominal Ba stoichiometry.

Subcoercive field non-linearities in 0.5(Ba0.7Ca0.3TiO3)-0.5(BaZr0.2Ti0.8O3) (BCTZ 50/50) thin film elaborated using pulsed laser deposition are studied using permittivity and phase angle of the third harmonic measurements as a function of the AC measuring field E A C and temperature. The global phase transition temperature T max for which the permittivity is maximum, decreases from 330 to 260 K when E A C increases. Rayleigh analysis of the AC field dependence of the relative permittivity shows a regular decrease in the domain wall motion contributions as temperature increases up to T max and an even more pronounced decrease above T max . This measurement reveals that the ferroelectric behavior subsists 70 K above the global phase transition. The phase angle of the third harmonic at temperatures below 275 K is characteristic of a conventional ferroelectric and from 275 K to T max = 330 K of a relaxor. Above T max , the thin film exhibits a peculiar phase angle of the third harmonic, which consists of − 180 ° → − 225 ° → + 45 ° → 0 ° instead of the − 180 ° → − 90 ° → 0 ° found for relaxor. This peculiar behavior is observed only on heating and is tentatively attributed to changes in the correlations between polar nanoregions. [ABSTRACT FROM AUTHOR]

We prepared a stacked structure consisting of a quasi-free-standing functional oxide thin film and a ceramic piezoelectric disk and observed the effect of the piezoelectric disk deformation on the resistance of the thin film. Epitaxial V2O3 films were grown by a pulsed laser deposition method on muscovite mica substrates, peeled off using Scotch tapes, and transferred onto piezoelectric elements. In this V2O3/insulator/top electrode/piezoelectronic disk/bottom electrode structure, the resistance of the V2O3 film displayed a variation of 60% by sweeping the piezoelectronic disk bias. With support from x-ray diffraction measurements under an electric field, a huge gauge factor of 3 × 103 in the V2O3 film was inferred. The sizeable resistance change in the V2O3 layer is ascribed to the piezo-actuated evolution of c/a ratios, which drives the material towards an insulating phase. A memory effect on the resistance, related to the hysteretic displacement of the piezoelectric material, is also presented. [ABSTRACT FROM AUTHOR]

Micro- or nano-structuring is essential in order to use Si as an anode material for lithium ion batteries. In the present study, we attempted to use Si wafers with a spiky microstructure (SMS), the so-called black-Si, prepared by a cryogenic reactive ion etching process with an SF6/O2 gas mixture, for Li half-cells. The SMS with various sizes of spikes from 2.0 μm (height)x0.2 μm (width) to 21 μmx1.0 μm was etched by varying the SF6/O2 gas flow ratio. An anode of SMS of 11 lmheight in average showed stable charge/discharge capacity and Coulombic efficiency higher than 99% for more than 300 cycles, causing no destruction to any part of the Si wafer. The spiky structure turned columnar after cycles, suggesting graded lithiation levels along the length. The present results suggest a strategy to utilize a wafer-based Si material for an anode of a lithium ion battery durable against repetitive lithiation/delithiation cycles. [ABSTRACT FROM AUTHOR]

Dielectric properties of Au/Ba0.6Sr0.4TiO3/La1.1Sr0.9NiO4 (Au/BST/LSNO) thin film capacitors were investigated versus excitation frequency and dc bias voltage. At low frequencies, Au/BST/LSNO capacitors exhibited a usual positive tunability [i.e., C(0V) > C(V)], while an unexpected negative tunable behavior appeared at higher frequencies. On the basis of the dielectric tunable theory and equivalent electrical circuits, a model describing the dielectric tunability of Au/BST/LSNO capacitors is proposed. The good agreement between fitted and experimental results shows that the resistance of LSNO bottom electrode in the Au/BST/LSNO capacitors plays an important role in the dielectric tunability transition from positive to negative with frequency. [ABSTRACT FROM AUTHOR]

Ion beam-assisted pulsed laser deposition with an Ar-oxygen ion mixture was used to prepare Ba0.6Sr0.4Ti0.7Zr0.3O3 (BSTZ) thin films on Pt-coated Si substrates. The ion beam with an anode voltage of 600 V was effective to reduce the thermal budget, i.e., to achieve similar crystallinity with approximately 100 °C lower deposition temperature compared to the cases without ionization. It was revealed that the dielectric properties (relative dielectric constant &eh;r and its electric field tunability), out-of-plane lattice parameter of (001)-oriented grains (a001), and the existence of (110)-oriented grains are correlated with one another. Elongation of a001 was suppressed, resulting in large &eh;r values comparable with that of a ceramic bulk of the same composition, in the BSTZ films that contain (110)-oriented grains. Less volume of amorphous BSTZ region is supposed to be playing an important role for the bulklike properties of these BSTZ films. [ABSTRACT FROM AUTHOR]

Epitaxial growth of Ba0.6Sr0.4Ti1-xZrxO3 (0≤x≤0.3) composition spread thin film library on SrRuO3/SrTiO3 layer by combinatorial pulsed laser deposition (PLD) is reported. X-ray diffraction and energy dispersive x-ray spectroscopy studies showed an accurate control of the film phase and composition by combinatorial PLD. A complex evolution of the microstructure and morphology with composition of the library is described, resulting from the interplay between epitaxial stress, increased chemical pressure, and reduced elastic energy upon Zr doping. Statistical and temperature-related capacitive measurements across the library showed unexpected variations in the dielectric properties. Doping windows with enhanced permittivity and tunability are identified, and correlated to microstructural properties. [ABSTRACT FROM AUTHOR]

High crystalline quality (Ba0.6Sr0.4)(Zr0.3Ti0.7)O3 (BSTZ) thin films were epitaxially grown by pulsed laser deposition on (001) SrTiO3 single crystal substrates. Their epitaxial nature was revealed by x-ray and electron diffraction. Thinnest film (∼9 nm) has largest out-of-plane lattice constant (4.135 Å) and tetragonality (1.06). Films are under compressive strain. Film thicknesses above ∼9 nm were started to relax as revealed from reciprocal space mapping. Thicknesses deduced from x-ray diffraction and transmission electron microscopy methods are in good agreement. Critical thickness to relieve strain of the BSTZ film is about 7.6±0.4 nm. [ABSTRACT FROM AUTHOR]

(BiFeO3)(1− x)Λ/(LaFeO3) xΛ superlattices (SLs) have been grown using pulsed laser deposition and studied by X-ray diffraction, transmission electron microscopy (TEM), and Raman spectroscopy. The composition is varied, 0.30 ≤ x ≤ 0.85, while the modulation period Λ is kept constant at about 10 nm. Unit cell doubling signatures typical of orthorhombic Pnma symmetry for x = 0.80 and 0.85 SLs and ¼{011} antiferroelectric PbZrO3-like reflections in SLs with 0.30 ≤ x ≤ 0.7 are detected by TEM showing a complex structural mixture at the nanoscale level. The Raman spectra confirm these observations and show a change in the SLs from a Pnma LaFeO3-like spectra for LaFeO3-rich period to a PbZrO3-like spectra for BiFeO3-rich period. Electron-phonon interactions and resonant-like excitations are also observed in the SLs. A temperature-dependent X-ray diffraction investigation shows a large shift of the paraelectric-antiferroelectric phase transition scaling with the BiFeO3 thickness. This shift is correlated with the strain state and can be explained by a strong interplay between octahedral rotation/tilt and antipolar Bi displacement. Thickness-temperature phase diagram is constructed and differs from previous report showing the extreme sensitivity of the BiFeO3 phase stability to strain effects and rotation/tilt degrees of freedom. [ABSTRACT FROM AUTHOR]

Ba xSrTiO3 () (BST) thin films were prepared on LaSrNiO4 (LSNO)/SrTiO3 (STO) structure by combinatorial pulsed laser deposition (comb-PLD). The capacitances of the Au/BST/LSNO capacitors exhibited strong frequency dependence especially when the applied frequency was higher than 10kHz. On the basis of an equivalent circuit model, we presented a theoretical simulation of the relationships between capacitance and frequency for the capacitors with different electrode serial resistances. Based on the fitting results, the observed strong frequency dependence of the measured capacitance at high frequency in our study could be ascribed to the large serial resistance of 750 for oxide electrode LSNO. Further simulation studies found that large serial resistance (1000 ) could result in an apparent deviation from the intrinsic dielectric properties especially at high frequencies (100kHz) for capacitors with capacitances above 1nF. Our results provide useful information for the design of all-oxide electronic devices. [ABSTRACT FROM AUTHOR]