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Abstract: In this study, we discuss the case for integration of epitaxial (Pb,La)(Zr,Ti)O3 (PLZT) thin films with silicon for electro-optic device applications. PLZT films, approximately 500 nm thick, were grown by on-axis radio frequency magnetron sputtering on CeO2/YSZ-buffered Si(100) substrate with a SrRuO3 electrode layer embedded between CeO2 and PLZT. The structural properties and surface topography of the different oxide layers were examined with X-ray diffraction analysis and atomic force microscopy. The perovskite thin films were predominantly (001)-oriented, with a (002) rocking curve halfwidth of approximately 0.3° and a surface roughness compatible with requirements for application in optical devices. The PLZT cation stoichiometry was assessed from quantitative X-ray photoelectron spectroscopy. These measurements uncovered a substantial depletion of lead in the film surface for layers deposited at substrate temperatures above ~600 °C, whereas the surface concentration of La, Zr and Ti remained virtually unaffected over a wide range of growth temperatures. [Copyright &y& Elsevier]

Heteroepitaxial LaFeO3(1 1 0) thin films with a thickness of 150 nm were grown on LaAlO3(0 0 1) by reactive sputtering in an inverted cylindrical magnetron geometry. Equilibrium conductivity was measured as a function of partial pressure of oxygen at T=1000 °C, and logσ plotted vs. logP(O2) showed a minimum in conductivity for P(O2)=10−11 atm and a linear response between 10−10 and 1 atm. This linear response makes thin films of LaFeO3 a promising material for oxygen sensor applications. We have also measured the time response of the film conductivity upon an abrupt change in the partial pressure of ambient oxygen from 10−2 to 10−3 atm, which was determined at 60 s for T=700 °C and <3.5 s at T=1000 °C. [Copyright &y& Elsevier]

Measurements of the surface impedance of DyBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (DyBCO) thin films have been made around 6 GHz by using the parallel plate resonator method with sapphire dielectrics. The films were deposited by RF magnetron sputtering on LaAlO/sub 3/ substrates to thicknesses between 20 and 320 nm. The change of the London penetration depth as a function of temperature is deduced from resonance frequency shifts. A generalized two fluid model is used to fit the data in terms of an effective penetration depth /spl lambda//sub eff/(0) at 0 K, taking into account the effect of grain boundary weak links. This analysis give an interpretation of the changes in /spl lambda//sub eff/(0) as a function of the film thickness and yields values for /spl lambda//sub eff/(0) around 160 nm for films thinner than 120 nm. [ABSTRACT FROM PUBLISHER]

Reports the local, nonvolatile electronic writing of epitaxial Pb(Zr0.52Ti0.48)O3/SrRuO3 heterostructures. Methods used; Details of the procedure.

We have studied how sub-bandgap photocurrents affect dynamic pyroelectric measurements in ferroelectric Pt/PbTiO3/Nb:SrTiO3 heterostructures. Currents generated in the PbTiO3 capacitors under pulsed laser illumination were found to be a combination of pyroelectric and photoelectric signals. We show that time-domain measurements can be used to separate the two contributions and obtain accurate pyroelectric hysteresis loops. Photocurrents, also present for excitation laser photon energies below the bandgap of the PbTiO3 ferroelectric, were assigned to charge carriers generated at the electrode interfaces. Hysteresis loops were observed for both current components, indicating that photocarrier extraction from the ferroelectric heterostructure can be controlled by choosing a suitable domain polarity. [ABSTRACT FROM AUTHOR]

Investigates the ferroelectricity in thin tetragonal single-crystalline perovskite films grown by off-axis magnetron sputtering. Measurement of the ferroelectric properties using electric force and piezoelectric microscopy; Time dependence of the measured signals showing a stable ferroelectric polarization in films.

In this article, we examine the initial polarization of PbTiO3 thin films grown epitaxially on SrRuO3 electrodes. It is found that the as-grown predominant polarization is directed toward the SrRuO3 bottom electrode in films thinner than 20 nm and directed toward the top surface in thicker films. The data is interpreted in terms of a Landau–Ginzburg–Devonshire model for a semiconducting ferroelectric with asymmetric boundary conditions. Based on the measured hysteresis loops and the stability of the two polarization directions with time, it is concluded that charged defects serve to impose a preferential downward polarization in very thin films. [ABSTRACT FROM AUTHOR]

The crystalline and dielectric properties of sputter deposited PbTiO3 thin films were investigated as a function of the film thickness and growth temperature. The crystalline quality was found to be independent of the film thickness from 2.4 to 200 nm. The capacitance of 0.12 mm2 Pt/PbTiO3/SrRuO3 and Pt/PbTiO3/Nb:SrTiO3 capacitors was found to deviate from the ideal parallel plate capacitance for PbTiO3 films thinner than 10 nm. The decrease in capacitance was consistent with field penetration into the electrodes. The surface Pb content, as determined from x-ray photoelectron spectroscopy, was found to decrease with increasing growth temperature from 700 to 760 °C. However, no change could be observed in the crystalline quality. [ABSTRACT FROM AUTHOR]

We demonstrate that a qualitative measure of the surface roughness can be obtained by using in situ reflection high energy electron diffraction. The in situ measurements of the surface roughness are found to be in agreement with the topography, as determined by ex situ atomic force microscopy. Relying on this method, we study the surface roughening during pulsed laser deposition of La0.7Sr0.3MnO3 and investigate the quality of (001)-oriented SrTiO3 substrates with a TiO2 termination. [ABSTRACT FROM AUTHOR]

We demonstrate that atomic force microscopy can be used to precisely manipulate individual sub-50 nm ferroelectric domains in ultrahigh density arrays on high-quality epitaxial Pb(Zr[sub 0.2]Ti[sub 0.8])O[sub 3] thin films. Control of domain size was achieved by varying the strength and duration of the voltage pulses used to polarize the material. Domain size was found to depend logarithmically upon the writing time and linearly upon the writing voltage. All domains, including those written with ∼100 ns pulses, remained completely stable for the 7 day duration of the experiment. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have investigated the possibility afforded by epitaxial ferroelectric oxide thin films to control and image locally the polarization field of ferroelectrics over large areas with submicron resolution, using the metallic tip of an atomic force microscope as a mobile top electrode and local probe of the ferroelectric properties. Atomically smooth films of Pb(Zr[sub 0.2]Ti[sub 0.8])O[sub 3], showing a root-mean-square roughness of typically a few angstroms, could be uniformly polarized and imaged over areas as large as 2500 μm[sup 2] without introducing any topographic disorder. Regular arrays of 100 nm wide lines and circular domains with a diameter less than 100 nm were written in arbitrary areas of the uniformly polarized regions. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The ferroelectric domain ground state of PbTiO3 thin films on Nb:SrTiO3 substrates has been studied as a function of film thickness. High resolution linear Qx x-ray diffraction profiles were recorded in order to probe the presence of stripe domains, which were invariably observed for as-grown samples. After photochemical treatment, films thinner than 50 unit cells were switched to a monodomain state that could be reversed upon subsequent annealing. The stripe-domain state is linked to a Qx modulation of the Qz parameter in the reciprocal space, which disappears upon switching. [ABSTRACT FROM AUTHOR]

We report on the stability of the La0.7Sr0.3MnO3 thin film surface when deposited on (111)-oriented SrTiO3. For ultrathin La0.7Sr0.3MnO3 films, an initial 3-dimensional morphology is observed, which becomes 2-dimensional with increasing film thickness. For even thicker samples, we show that the surface morphology evolves from 2-dimensional to 3-dimensional and that this observation is consistent with an Asaro-Tiller-Grinfeld instability, which can be controlled by the deposition temperature. This allows for synthesis of films with step-and-terrace surfaces over a wide range of thicknesses. Structural characterization by x-ray diffraction and transmission electron microscopy shows that the films are strained to the SrTiO3 substrate and reveals the presence of an elongated out-of-plane lattice parameter at the interface with SrTiO3. [ABSTRACT FROM AUTHOR]

Studies of oxide interfaces, and how they affect physical properties, have recently gained large attention. For ferroelectric materials, the evolution of the order parameter close to an interface is important to understand regarding the stability of the ferroelectric phase, and how to optimize devices taking advantage of the polarization at the interface. Here we employ electron energy loss spectroscopy (EELS) in scanning transmission electron microscopy to compare the electronic and structural properties in both bulk and interface regions of epitaxial PbTiO3 thin films grown on SrTiO3 substrates. At the interface, changes in EELS spectra of the Ti-L3,2 and O-K edges, as compared to the bulk of the thin film, reveal a reduction in the hybridization of Ti 3d and Pb 6sp states with O 2p, and thus tetragonal distortion of the TiO6 octahedron. Real-space multiple-scattering calculations of the O-K edge support the experimental results. Moreover, the analysis of the Ti-valence reveals that the change is gradual over ∼2-3 nm. The data implies a decreasing ferroelectric order parameter over ∼2-3 nm close to the PbTiO3/SrTiO3 interface with a nonzero value at the interface with an additional screening of the polarization over ∼1-2 nm into the SrTiO3 substrate from the Ti atoms. [ABSTRACT FROM AUTHOR]

Observation of stripe domains in PbTiO3 thin films using standard x-ray diffraction analysis at room temperature is discussed. High-quality c-axis oriented thin films of varying thickness, from 6 to 210 unit cells, were grown on buffered NH4–HF etched SrTiO3(001) and Nb:SrTiO3(001) substrates using off-axis radio frequency magnetron sputtering. High-resolution linear Qx scans reveal a superstructure around the specular Bragg peaks, consistent with the presence of ferroelectric stripe domains. For thin samples, the stripe width is found to be proportional to the square root of the film thickness, with random in-plane orientation of domains. For films with a thickness of more than ∼100 unit cells, both monodomain samples and stripe domains were observed. We present evidence for the presence of a threshold depolarization field, above which there is a monotonically decreasing relationship between the domain width and the depolarization field. Furthermore, simulations show that random variations in size of the domains affect the separation of the diffuse scattering peaks from that of the specular reflection. [ABSTRACT FROM AUTHOR]

In this study, we report on the magnetic domain formation in ultrathin blanket films and patterned micro- and nanostructures of ferromagnetic (FM) La0.7Sr0.3MnO3 single-layers and antiferromagnetic (AF)/ferromagnetic LaFeO3/La0.7Sr0.3MnO3 bilayers, as investigated by soft x-ray photoemission electron microscopy. In single-layer La0.7Sr0.3MnO3, the domain size is significantly reduced compared to that found in thicker layers, and rectangular micromagnets display metastable multidomain states distinctly different from the flux-closure ground states commonly found in thicker elements. In the LaFeO3/La0.7Sr0.3MnO3 bilayers, complex multidomain patterns are observed for blanket films and patterned magnets with robust perpendicular (spin-flop) coupling between spins in the AF and FM layers. By thermal cycling of the sample through the La0.7Sr0.3MnO3 Curie temperature, we find that the native antiferromagnetic domain pattern of LaFeO3 pins the location of domain boundaries in the adjacent La0.7Sr0.3MnO3 layer. [ABSTRACT FROM AUTHOR]

An oxygen vacancy driven structural response at the epitaxial interface between La0.7Sr0.3MnO3/SrTiO3 films and SrTiO3 substrates is reported. A combined scanning transmission electron microscopy and electron energy loss spectroscopy study reveal the presence of an elongated out-of-plane lattice parameter, coupled to oxygen vacancies and reduced manganese oxidation state at the La0.7Sr0.3MnO3/SrTiO3 side of the interface. Density functional theory calculations support that the measured interface structure is a disordered oxygen deficient brownmillerite structure. The effect of oxygen vacancy mobility is assessed, revealing an ordering of the vacancies with time. [ABSTRACT FROM AUTHOR]

We present a detailed structural study of tensile-strained La0.7Sr0.3MnO3thin films. We use the substratemiscutto control the number of rhombohedral variants in the films and study the in-plane order and structural distortions. Using high-resolution X-ray diffraction, we demonstrate that step-edge induced lattice modulations occur in 4-variant films, whereas periodic twinning is the dominant in-plane order for 2-variant films. We show that the in-plane twinning angle is almost completely relaxed. However, the relaxation of shear strain by the out-of-plane twinning angle and the monoclinic distortion is only partial. Furthermore, the film thickness dependence of the domain width reveals that domain formation is a universal mechanism for shear strain relaxation. Finally, we show that the structural response to the transition from the paramagnetic to the ferromagnetic phase of La0.7Sr0.3MnO3at 345 K is smaller in 4-variant films compared to 2-variant films. [ABSTRACT FROM AUTHOR]

Abstract: We present a study of the surface stoichiometry and contamination of La0.7Sr0.3MnO3 thin films following exposure to air and subsequent in vacuo preparation. Samples were studied using both soft X-ray synchrotron photoemission (hν =150 to 350eV) and traditional Mg-Kα XPS (hν =1253.6eV) whilst annealing incrementally to ≈510°C in low pressures of O2. In all cases, a Mn depleted and Sr rich surface oxide layer is observed, it is of reduced crystalline quality and is charge depleted. This surface layer is weakly affected by subsequent annealing, and is partially reversed by annealing in higher O2 pressure. Surface carbon contamination is incrementally removed by annealing at increased temperatures, and at 270°C, it is reduced to ≈0.4% of the topmost unit cell. The modification of the surface stoichiometry and electronic properties is consistent with the reported loss of magnetic properties in thin LSMO films. [Copyright &y& Elsevier]

Here, we demonstrate a structural interaction between LaAlO3 thin films and SrTiO3 substrates using highresolution x-ray diffraction. X-ray diffraction profiles reveal the presence of periodic lattice distortions in the LaAlO3 thin films, whose in-plane periodicity is determined by the miscut angle and miscut direction of the substrate. We show that the structural distortions in LaAlO3 thin films induce similar distortions in the SrTiO3 substrate. [ABSTRACT FROM AUTHOR]

Abstract: Surface modifications through line etching of SrRuO3 thin films have been carried out using a scanning tunneling microscope under ambient conditions. The line etching is found to be dependent on both bias voltage and scan speed for a given number of scan repetitions. We observe that an applied voltage above a threshold value is required for successful line etching. The depth of the etched lines is increasing with increasing bias voltage and scan repetitions as well as with decreasing scan speed. Moreover, sub-50 nm laterally confined mesa structures could be reproducibly etched on the SrRuO3 thin film surfaces. [Copyright &y& Elsevier]

Abstract: In this study, we examine the growth conditions for Pb0.92La0.08Zr0.4Ti0.6O3 thin films with a linear electro-optical response. Films grown on SrTiO3(100) substrate show good crystalline quality and surface smoothness, if deposited within a narrow range of substrate temperatures around 530 °C. Such films had a (002) rocking curve full width at half maximum less than 0.2°, and a surface roughness less than 0.4 nm. X-ray photoelectron spectroscopy analysis confirmed the absence of surface impurity phases and revealed a single oxidation state for Pb2+, Zr4+, and Ti4+cations. Good crystalline quality and a smooth film surface are required for the use of these materials in optical device applications. [Copyright &y& Elsevier]

We report on the fabrication of a novel surface acoustic wave device based on piezoelectric interdigital transducers designed in high quality films of Pb(Zr0.2Ti0.8)O3 grown by RF magnetron sputtering. The approach followed is to replace the conventional metallic interdigital transducers by piezoelectric ones consisting of a series of ferroelectric domains with alternating polarization states. The artificial modification of the ferroelectric domain structure is realized by using an atomic force microscope as a local electric field source. A 1.2 μ m wavelength device has been realized and its transmission properties simulated. [ABSTRACT FROM AUTHOR]

Presents research which tuned the critical temperature of the high-temperature superconducting cuprate gadolinium barium copper oxide (GdBa2Cu3O7-x). Use of the polarization field of the ferroelectric oxide lead zirconate titanate (Pb(ZrxTi1-x)O3); Slightly underdoped samples compared with more underdoped ones; Nature of the transition from superconducting to insulating behavior.

We have studied the origin of suppressed remanent polarization in 4-variant BiFeO3 by correlating microscopic observations of ferroelectric/ferroelastic domain structures and ferroelectric measurements of (001) epitaxial BiFeO3 thin films with 2- and 4-ferroelastic domain variants. Piezoelectric force microscopy revealed that domain wall pinning was the cause of the reduced polarization observed in 4-variant BiFeO3. Using repetitive switching, the unswitched domains were completely switched and the remanent polarization reached a value comparable to 2-variant BiFeO3. These results demonstrate that control of ferroelastic domains in rhombohedral systems is necessary in order to obtain high performance and reliable ferroelectric and magnetoelectric devices. [ABSTRACT FROM AUTHOR]

We have studied spontaneous structural ordering in epitaxial barium stannate thin films, grown on SrTiO3(001) substrates by pulsed laser deposition. X-ray diffraction analysis revealed satellite reflections around the Bragg peaks, indicative of nanoscale periodic ordering in the out-of-plane direction. We find that mass transport strongly affects this spontaneous ordering, and that the thin film growth rate can be used to tune the periodicity of the superlattices, here between 4.3 and 57.7 nm. [ABSTRACT FROM AUTHOR]

We have analyzed the defect contributions to the in-plane polarization switching of epitaxial (001) BiFeO3 thin films on (110) TbScO3 substrates. Interdigitated electrodes were patterned with respect to ferroelectric stripe domains in the BiFeO3 film. Polarization measurements exhibited a clear double hysteresis caused by the presence of a static defect field (∼40 kV/cm); the field resulted from ordered defect-dipoles initially aligned to the spontaneous polarization. By monitoring the defect field, both realignment and disassociation of the defect-dipoles were demonstrated. These results establish the arrangement of defect-dipoles in epitaxial ferroelectric thin films, guiding technologies and opening an avenue for defect related studies. [ABSTRACT FROM AUTHOR]

Epilayer control of photoassisted oxidation and reduction on the ferroelectric PbTiO3 polar surface was investigated. Photo-oxidation of a AgNO3 electrolyte resulting in formation of Ag7NO11 particles was observed on the PbTiO3/Nb:SrTiO3 film surface; whereas PbTiO3/SrRuO3/SrTiO3 leads to AgNO3 reduction under UV illumination. The oxidation reaction resulting in the formation of Ag7NO11 is explained in terms of a rectifying interface between PbTiO3 and Nb:SrTiO3, controlling the charge transport during UV photocatalysis. [ABSTRACT FROM AUTHOR]

• Enhanced magnetic dichroism signal is found along edges of embedded LSMO nanomagnets. • XRD measurements reveal asymmetric changes to lattice parameters. • Magnetic domains near edges reorganize close to T C. When thin films are patterned to realize nanoscale device geometries, maintaining their structural integrity is key to the quality of their functional properties. The introduction of new surfaces and interfaces by lateral modifications may alter material properties as well as the expected device functionality. In this study, two different techniques for nanoscale patterning of epitaxial thin films of La 0.7 Sr 0.3 MnO 3 are used to investigate the effects on their ferromagnetic properties and film crystalline structure. Nanomagnets are realized as free-standing structures and embedded ferromagnets in a paramagnetic matrix, respectively. We find that the magnetic dichroism signal in x-ray spectomicroscopy is stronger along the edges of the embedded magnets close to T C. X-ray-diffraction measurements reveal a reduction of their in-plane lattice parameters. We discuss how in-plane stress from the nanomagnet surroundings can affect the magnetic properties in these structures. [ABSTRACT FROM AUTHOR]

In this study, we rely on low-angle annular dark-field scanning transmission electron microscopy to probe the interface strain profile in epitaxial PbTiO3/SrTiO3 thin-films. All samples displayed a compressively strained layer at the PbTiO3/SrTiO3 interface, with the strain vector parallel to the polarization direction. The width of the strained layer was found to be ∼15–30 Å, dependent on the electrode environment. Our findings open a perspective to use interface strain engineering in combination with control of electrostatic boundary conditions as a tool to monitor the effective interface polarization. These findings have implications for future use of ferroelectrics in electronic and mechanical devices. [ABSTRACT FROM AUTHOR]

Using high-quality epitaxial c-axis Pb(Zr0.2Ti0.8)O3 films grown by off-axis magnetron sputtering onto metallic (001) Nb-doped SrTiO3 substrates, a nonconventional thin-film surface acoustic wave device based on periodic piezoelectric transducers was realized. The piezoelectric transducers consist of a series of ferroelectric domains with alternating polarization states. The artificial modification of the ferroelectric domain structure is performed by using an atomic force microscope tip as a source of electric field, allowing local switching of the polarization. Devices with 1.2 and 0.8 μm wavelength, defined by the modulation period of the polarization, and corresponding to central frequencies in the range 1.50–3.50 GHz have been realized and tested. [ABSTRACT FROM AUTHOR]

We observe an induced switchable magnetic moment of 1.6±0.40μB/Fe for the nominally antiferromagnetic LaFeO3 extending two to four interface layers into the non-charge transfer system La0.7Sr0.3MnO3/LaFeO3/SrTiO3(111). Simultaneously a mismatch of oxygen octahedra rotations at the interface implies an atomic reconstruction of reduced symmetry at the interface, reaching two to five layers into LaFeO3. Density functional theory of a structure with atomic reconstruction and different correlation strength shows a ferrimagnetic state with a net Fe moment at the interface. Together these results suggest that engineered oxygen octahedra rotations, affecting the local symmetry, affect electron correlations and can be used to promote magnetic properties. [ABSTRACT FROM AUTHOR]

Using soft x-ray spectromicroscopy, we investigate the magnetic domain structure in embedded nanomagnets defined in La0.7Sr0.3MnO3 thin films and LaFeO3/La0.7Sr0.3MnO3 bilayers. We find that shape-controlled antiferromagnetic domain states give rise to a significant reduction of the switching field of the rectangular nanomagnets. This is discussed within the framework of competition between an intrinsic spin-flop coupling and shape anisotropy. The data demonstrates that shape effects in antiferromagnets may be used to control the magnetic properties in nanomagnets. [ABSTRACT FROM AUTHOR]

A correction to the article "Epilayer control of photodeposited materials during UV photocatalysis" is presented.