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The atomic and electronic structures at interfaces in thin films are typically different from the bulk and are vitally important in determining the physical properties of thin films. The interface between SrVO3, chosen as a prototype for vanadium-based perovskite materials in this work, and LaAlO3 substrate is investigated by scanning transmission electron microscopy, electron energy-loss spectroscopy, and theoretical multi-electron calculations. Extra electrons have been detected on the interface layer by comparing the energy-loss near-edge structures of V-L3,2 edges to those from the film far from the interface. Monochromated EELS and theoretical calculations for SrVO3, VO2, and V2O 3 support this conclusion. The extra electrons appear to originate from a change in the local bonding configuration of V at the La-O terminated substrate surface as determined by Z-contrast imaging. © 2011 American Institute of Physics.

The switching kinetics in epitaxial (001)-, (110)-, and (111)-oriented BiFeO3 thin films were investigated as a function of applied field and time. It was found that the ferroelectric switching behavior obeys the Kolmogorov-Avrami-Ishibashi theory only in the high field range. The detailed behavior depends on the film orientation. A comparison with standard systems, such as epitaxial Pb (Zr0.2 Ti0.8) O3 films, reveals some similarities as well as some differences. For instance, the presence of 109° and 71° ferroelastic domain walls might be ruled out as the source of the decrease in switched polarization at low applied fields, in contrast to what is the case for a/c domain walls in tetragonal Pb (Zr 0.2 Ti0.8) O3. © 2010 American Institute of Physics.

A methodology is presented to extract the relevant quantities of a Schottky contact, in the specific case of metal-ferroelectric-metal structures, by using the metal-ferroelectric interface. The models are applied to Pb(Zr, Ti)O3 thin films with different Zr/Ti ratios, fabricated by different deposition methods and having different Schottky contacts.

Leakage characteristics of ferroelectric thin films were studied to determine the effects of contact electrodes.

A study investigated the effect of film thickness on structural and electrical properties of epitaxial lead zirconate titanate films that were prepared by pulsed laser ablation and characterized by four-circle X-ray diffraction, pulsed switching measurements and transmission electron microscopy. The study demonstrated a strong dependence of the domain structure of the film on the thickness of the ferroelectric layer.

A study was conducted to analyze the effects of thin film deposition conditions on the microstructural, microwave and magnetic characteristics of pulsed laser deposited epitaxial thin films of barium ferrite on single crystal sapphire substrates. Results indicated that the use of the films for device applications correlated with the need to reduce the deposition temperature and the post-annealing requirement.

A study was conducted on epitaxial ferroelectric thin films in connection with their potential applications as elements of non-volatile random access memories and static ferroelectric random access memories, optical waveguides and pyroelectric detectors. The experiment focused on the effect of La0.5Sr0.5CoO3 electrode layer thickness and configuration on the microstructure of PbZr0.2Ti0.8O3 films on SrTiO3 substrates in conjunction with previous theoretical investigations.

The effect of 90 high energy (MeV) oxygen ion induced disorder on the magnetotransport in epitaxial La0.7Ca0.3MnO3 (LCMO) thin films was investigated. Epitaxial films of LCMO were subjected to irradiation with 90 MeV oxygen ions at different dose values. The magnetization, structural and magnetotransport characteristics were analyzed as a function of the ion dose. Experimental results showed that there is swelling in the surface morphology of the LCMO thin films probably caused by subsurface clustering of point defects.

In superlattice heterostructures with alternating layers of Y3Fe5O12 and EuBi2Fe5O12 grown by pulsed-laser deposition, the spins in the Y3Fe5O12 layer always prefer to lie in the plane. In the other layer, the spin direction changes from normal to the film plane to in-plane as its thickness declines to less than that of the Y3Fe5O12 layer. The addition of Y3Fe5O12 layers reduces the magnitude of the anistropy while producing narrower EuBi2Fe5O12 ferrimagnetic resonance lines.

Research was conducted to examine the imprint characteristics of fully integrated ferroelectric lead zirconate titanate based capacitors. Conducting perovskite La-Sr-Co-O electrodes were used to fabricate the ferroelectric capacitors. Imprints on the capacitors revealed a small temperature dependence over the range that was studied. Results revealed that the unidirectional pulse voltage amplitude had a larger influence on the imprint.

A study was conducted to analyze the effect of deviation from the nominal La0.5Sr0.5CoO3 composition of the electrode and to determine temperature dependencies of the degradation phenomenon of ferroelectric capacitors. A significant variation in electrode composition was analyzed. Results revealed that ferroelectric capacitors exhibited zero fatigue in different cycles due to the oxide electrodes yet an asymmetry in the polarization-voltage hysteresis loops could be observed.

A study of ac-susceptibility of the intermetallic system Zr(1-x)Ho(x)Co2 with the help of a Sumitoma ac susceptometer at temperatures between 13 and 300 K indicates variations in magnetic ordering temperature (Tc) and order of magnetic transition with value of x. Tc decreases with hydrogenation and increases with an increase in value of x. The system exhibits Pauli paramagnetism at an x value of 0. Charge transfer effects cause the mitigation of exchange interactions during hydrogen absorption.

Epitaxially grown single-crystalline La-Ca-Mn-O thin films show a temperature dependent, isotropic and negative, giant magnetoresistance (GMR) effect. The GMR in lanthanum magnetite field is a result of the grain boundaries. This GMR effect is much greater than the one for multilayer films, and is related to the semiconductor-to-metal transition.

Disappearance of the first order transition is observed in Zr(1-x)Ho(x)Co(2) Laves phase intermetallic systems. The disappearance is detected by performing electrical resistivity studies on Zr(1-x)Ho(x)Co(2), and the disappearance phenomena is directly proportional to HO concentrations. The spin fluctuations in HO produce anomalies such as resistivity minima in moderate HO concentrations. Spin fluctuations are caused by the correlation between the rare earth element movement near the magnetic ordering temperature.

Quasiparticle injection devices (QPIDs) with low-Tc superconductors (LTS) have been investigated with all types of injections sources to achieve the desired nonequilibrium transport for device applications. Quasiparticles can be spin-polarized. NSMO and LNO heterostructures were fabricated on (100) LaA1O(sub3) substrates by pulsed laser deposition, to study the quasiparticle injection effects in high-Tc superconducting thin films. A current grain grater than nine was obtained for spin-polarized QPIDs.

The local dynamics of ferroelectric domain polarization are uniquely investigated with sub-20-nm resolved maps of switching times, growth velocities, and growth directions. This is achieved by analyzing movies of hundreds of consecutive high speed piezo force microscopy images, which record domain switching dynamics through repeatedly alternating between high speed domain imaging and the application of 20-nanosecond voltage pulses. Recurrent switching patterns are revealed, and domain wall velocities for nascent domains are uniquely reported to be up to four times faster than for mature domains with radii greater than approximately 100 nm. Switching times, speeds, and directions are also shown to correlate with local mechanical compliance, with domains preferentially nucleating and growing in compliant sample regions while clearly shunting around locations with higher stiffness. This deterministic switching behavior strongly supports a defect-mediated energy landscape which controls polarization reversal, and that can therefore be predicted, modeled, and even manipulated through composition, processing, and geometry. Such results have important implications for the practical performance of ferroelectric devices by enabling guided optimization of switching times and feature densities, while the methods employed provide a new means to investigate and correlate dynamic functionality with mechanical properties at the nanoscale. [ABSTRACT FROM AUTHOR]

Ferroelectric domain structures of (001)c, (101)c, and (111)c oriented epitaxial BiFeO3 thin films were studied by using the phase-field approach. Long-range elastic and electrostatic interactions were taken into account. The effects of various types of substrate constraint on the domain morphologies were systematically analyzed. It is demonstrated that domain structures of BiFeO3 thin films could be controlled by selecting proper film orientations and substrate constraint. The dependence of the {110}c-type domain wall orientation on substrate constraint for the (001)c oriented BiFeO3 thin film was also discussed. [ABSTRACT FROM AUTHOR]

A single-domain thermodynamic theory is employed to predict the spontaneous polarizations of (001)c, (101)c, and (111)c oriented epitaxial BiFeO3 thin films grown on dissimilar substrates. The effects of various substrate-induced strains on the spontaneous polarization were studied. The dependences of the spontaneous polarization on film orientations and the types of substrate-induced strains were analyzed. [ABSTRACT FROM AUTHOR]

Scaling of the structural order parameter, polarization, and electrical properties was investigated in model ultrathin epitaxial SrRuO3/PbZr0.2Ti0.8O3/SrRuO3/SrTiO3 heterostructures. High-resolution transmission electron microscopy images revealed the interfaces to be sharp and fully coherent. Synchrotron x-ray studies show that a high tetragonality (c/a∼1.058) is maintained down to 50 Å thick films, suggesting indirectly that ferroelectricity is fully preserved at such small thicknesses. However, measurement of the switchable polarization (ΔP) using a pulsed probe setup and the out-of-plane piezoelectric response (d33) revealed a systematic drop from ∼140 μC/cm2 and 60 pm/V for a 150 Å thick film to 11 μC/cm2 and 7 pm/V for a 50 Å thick film. This apparent contradiction between the structural measurements and the measured switchable polarization is explained by an increasing presence of a strong depolarization field, which creates a pinned 180° polydomain state for the thinnest films. Existence of a polydomain state is demonstrated by piezoresponse force microscopy images of the ultrathin films. These results suggest that the limit for a ferroelectric memory device may be much larger than the fundamental limit for ferroelectricity. [ABSTRACT FROM AUTHOR]

A modified model of metal-semiconductor contacts is applied to analyze the capacitance-voltage and current-voltage characteristics of metal-ferroelectric-metal structures. The ferroelectric polarization is considered as a sheet of surface charge situated at a fixed distance from the interface. The presumable high concentration of structural defects acting as active electric traps is taken into account by introducing a deep acceptorlike level. The model is applied on a set of metal-Pb(Zr,Ti)O3-metal samples with different Zr/Ti ratios, deposited by different methods, and having different thicknesses, electrode materials, and electrode areas. Values around 1018 cm-3 were estimated for the hole concentration from capacitance-voltage measurements. The space-charge density near the electrode, estimated from current-voltage measurements, is in the 1020–1021 cm-3 range. The total thickness of the interface layer ranges from 3 to 35 nm, depending on the Zr/Ti ratio, on the shape of the hysteresis loop, and on the electrode material. The simulated I-V characteristics is fitted to the experimental one using the potential barrier and Richardson’s constant as parameters. The potential barrier is determined to be in the 1.09–1.37 eV range and Richardson’s constant is 520 A cm-2 K-2. [ABSTRACT FROM AUTHOR]

The synthesis and fundamental material properties of layered TiAl/Cu/Ta electrodes were investigated to achieve the integration of Cu electrodes with high-dielectric constant (κ) oxide thin films for application to the fabrication of high-frequency devices. The Ta layer is an excellent diffusion barrier to inhibit deleterious Cu diffusion into the Si substrate, while the TiAl layer provides an excellent barrier against oxygen diffusion into the Cu layer to inhibit Cu oxidation during the growth of the high-κ layer in an oxygen atmosphere. Polycrystalline (Ba[sub x]Sr[sub 1-x])TiO[sub 3] (BST) thin films were grown on the Cu-based bottom electrode by rf magnetron sputtering at temperatures in the range 400–600 °C in oxygen, to investigate the performance of BST/Cu-based capacitors. Characterization of the Cu-based layered structure using surface analytical methods showed that two amorphous oxide layers were formed on both sides of the TiAl barrier, such that the oxide layer on the free surface of the TiAl layer correlates with TiAlO[sub x], while the oxide layer at the TiAl/Cu interface is an Al[sub 2]O[sub 3]-rich layer. This double amorphous barrier layer structure effectively prevents oxygen penetration towards the underlying Cu and Ta layers. The TiAlO[sub x] interfacial layer, which has a relatively low dielectric constant compared with BST, reduced the total capacitance of the BST thin film capacitors. In addition, the layered electrode-oxide interface roughening observed during the growth of BST films at high temperature, due to copper grain growth, resulted in large dielectric loss on the fabricated BST capacitors. These problems were solved by growing the BST layer at 450 °C followed by a rapid thermal annealing at 700 °C. This process significantly reduced the thickness of the TiAlO[sub x] layer and interface roughness resulting in BST capacitors exhibiting properties suitable for the fabrication of high-performance high-frequency devices. In summary, relatively high dielectric constant (280), low dielectric loss (0.007), and low leakage current (<2×10[sup -8] A/cm[sup 2] at 100 kV/cm) were achieved for BST thin film capacitors with Cu-based electrodes. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Landau–Devonshire-type phenomenological thermodynamic theory is employed to explain the electric field dependence of piezoelectric properties of tetragonal single domain PbZr[sub x]Ti[sub 1-x]O[sub 3] (PZT). The strong nonlinearity of the converse piezoelectric coefficient under a large external electric field is proved to be intrinsic both in bulk crystal and epitaxial tetragonal PZT thin films. The tunability of piezoelectric responses by an external electric field and its dependence on the film/substrate misfit and elastic compliance of thin films are characterized quantitatively. The theoretical predictions are in good agreement with the experimental results of piezoresponse scanning microscopy. Due to the large tunability of piezoresponse in it, PZT 50/50 (x=0.5) epitaxial film is a promising candidate for use in future tunable devices. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have performed depth profile studies of the structure of PbZr[sub 0.2]Ti[sub 0.8]O[sub 3] films of different thicknesses deposited on SrTiO[sub 3] substrates prepared by pulsed laser deposition, using grazing incident x-ray scattering (GIXS). The in-plane structure of the films reveals these consist of up to three domains, one c-axis domain, and two a-axis domains, denoted al and a2. GIXS measurements show the evolution of in-plane compression of the lattice parameter as a function of depth within the films, particularly in the a1 domains. This strain evolution is accompanied by the presence of twist grain boundaries in the plane in some films. The measured in-plane lattice parameters are asymmetric, which suggests an orthorhombic distortion of the lattice in the plane of the films. [ABSTRACT FROM AUTHOR]

We studied the effect of ion damage on the properties of 50 keV Ga[sup +] focused ion beam fabricated lead-zirconate-titanate capacitors as a function of the ion dose. We observed significant modification in the chemical composition of the damaged layer due to loss of lead and oxygen, and gallium impurity accumulation. The 5-10 nm thick damaged layer becomes dielectric after annealing and does not recover its ferroelectric properties. This dielectric layer substantially reduces the actual volume of the ferroelectric material in sub-100 nm structures, and can affect their performance. [ABSTRACT FROM AUTHOR]

Voltage-modulated scanning force microscopy (Piezoresponse microscopy) is applied to investigate the domain structure in epitaxial PbZr[sub 0.2]Ti[sub 0.8]O[sub 3] ferroelectric thin films grown on (001) SrTiO[sub 3]. By monitoring the vertical and lateral differential signals from the photodetector of the atomic force microscope it is possible to separate out and observe the out-of-plane and in-plane polarization vectors in the thin film individually. The relative orientation of the polarization vectors across a 90° domain wall is observed. Nucleation of new reversed 180° domains at the 90° domain wall is studied and its impact on the rotation of polarization within the a domain is analyzed as a function of reversal time. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Epitaxial ferroelectric films undergoing a cubic-tetragonal phase transformation relax internal stresses due to the structural phase transformation and the difference in the thermal expansion coefficients of the film and the substrate by forming polydomain structures. The most commonly observed polydomain structure is the c/a/c/a polytwin which only partially relieves the internal stresses. Relatively thicker films may completely reduce internal stresses if all three variants of the ferroelectric phase are brought together such that the film has the same in-plane size as the substrate. In this article, we provide experimental evidence on the formation of the three-domain structure based on transmission electron microscopy in 450 nm thick (001) PbZr[sub 0.2]Ti[sub 0.8]O[sub 3] films on (001) SrTiO[sub 3] grown by pulsed laser deposition. X-ray diffraction studies show that the film is fully relaxed. Experimental data is analyzed in terms of a domain stability map. It is shown that the observed structure in epitaxial ferroelectric films is due to the interplay between relaxation by misfit dislocations at the deposition temperature and relaxation by polydomain formation below the phase transformation temperature. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Epitaxial La[sub 0.7]Ca[sub 0.3]MnO[sub 3] thin films on the SrTiO[sub 3](100) surface have been irradiated with 250 MeV Ag[sup 17+] ions at different nominal fluence values in the range of 5×10[sup 10]–4×10[sup 11] ions/cm[sup 2], resulting in columnar defects. At low fluences these defects cause changes in material properties that are small and scale linearly with dosage. Above a threshold fluence value ∼3×10[sup 11] ions/cm[sup 2] dramatic changes are observed, including an order of magnitude increase in the resistivity and 50 K drop in the Curie temperature. Transmission electron microscopy measurements show that the changes are associated with a phase transformation of the undamaged region between the columnar defects. The transformed phase has a diffraction pattern very similar to that seen in charge-ordered La[sub 0.5]Ca[sub 0.5]MnO[sub 3]. We propose that above a critical level of ion damage, strains caused by the presence of the columnar defects induce a charge-ordering phase transition that causes the observed dramatic changes in physical properties. We speculate that a conceptually similar surface-induced charge ordering may be responsible for the “dead layer” observed in very thin strained films, and the dramatic changes in optical properties induced by polishing, and that an impurity-induced charge ordering causes the extreme sensitivity of properties to lattice substitution. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The pulsed laser deposition technique is used to fabricate epitaxial Y3Fe5O12(YIG)/Bi3Fe5O12 (BIG) and YIG/Eu1Bi2Fe5O12 (EBIG) heterostructures on (111) aligned single-crystalline gadolinium-gallium-garnet substrates. The magnetic properties of multilayered heterostructures are better than those of single crystalline monolayers. The in-plane saturation magnetic moments are significant in YIG/BIG heterostructures with an optimum value nearing the value in bulk YIG. YIG/EBIG heterostructures exhibit a thorough magnetic moment realignment in the out-of-plane direction.

Spinodally decomposed and deformed bulk Cu-20 Ni-20 Fe alloys having a perfect ultrafine ferromagnetic phase are subjected to a giant magnetoresistance effect. The ferromagnetic phase is present in these alloys as dispersed particles or as layered superlattices. The magnetoresistance ratio is increased when the particle geometry of the alloys are optimized by heat-treatment and uniaxial plastic deformation.

The extraordinary Hall effect (EHE) in ultrathin coherent ferromagnetic tau(Mn,Ni)0.60Al0.40 films grown by molecular beam epitaxy was investigated using x-ray scattering and cross-sectional transmission electron microscopy. The results showed that the perpendicularly magnetized films exhibited EHE resistivities which saturated in the 3.3 to 7.1 microohm-cm range at room temperature. Switching between magnetic states took place at distinct field values.

A combination of computer simulations and the phase-field approach is employed to study the ferroelectric domain structures of the differently oriented epitaxial BiFe[O.sub.3] thin films. The appropriate selection of film orientations and substrate constraint is shown to be essential for controlling the domain structures of the films.

The effects of the various substrate-induced strains on the spontaneous polarization of the epitaxial BiFe[O.sub.3] thin films that are grown on different substrates are studied. The substrate effect highly depends on the orientations and the types of strains induced in the films.

Results on strained La(sub 2/3)Ca(sub 1/3)MnO3 (LCMO) films that are able to distinguish between true strain effects and effects due simply to the reduced film thickness are reported. The films on SrTiO3 and LaAlO3 are elastically strained and those on NdGao3 are only slightly strained.

Film deposition, oxidation and materials integration in the system of layered TiAl/Cu/Ta electrodes were investigated to obtain the integration of Cu electrodes with high-dielectric constant (kappa) oxide thin films. These can be applied to the fabrication of high-frequency devices.

Focuses on a study that presented results of structural and microanalytical studies on sintered iron rare-earth boron permanent magnets. Details of the experiment; Results; Conclusion.

Deals with ac-susceptibility study on the intermetallic compounds Zr[sub1-x]Ho[subx]Co[sub2]. Description of the magnetic transition; Spin reorientation; Effect of hydrogen absorption on the exchange interactions.

Deals with the electrical resistivity studies that have been carried out on the C 15-type Laves phase intermetallic compounds and their hydrides in the temperature range 16-300 K. Experimental details; Results and discussion; Conclusion.

Presents a microstructure based magnetization reversal model for sintered Fe-Nd-B magnets. Background on a magnetization reversal model in optimally treated magnets; Implications of the model; Details of experimental procedures.

Analyzes epitaxial relations between in situ superconducting YBa[sub2]Cu[sub3]O[sub7-x] thin films and BaTiO[sub3]/MgAl[sub2]O[sub4]/Sl substrates. Application of transmission electron microscopy in investigating the layers; Observations on the behavior of the substrates; Evaluation of the microstructure of the films and their superconducting properties.

Deals with a study which investigated the interaction of domain walls with microstructural features in sintered Fe-Nd-B magnets by Lorentz microscopy using a high-voltage transmission electron microscope. Experimental details; Results and interpretation; Discussion and conclusions.

Presents a study that characterized defects and structural interfaces in superconducting Bi-Sr-Ca-Cu-O by transmission electron microscopy. Description of the superconducting phase; Information on the main type of point defect; Importance of the characterization of the nature of grain boundaries and the phases that form at these interfaces in understanding the transport properties.

Focuses on a study which presented a doping mechanism model in bismuth superconductors. Information high-temperature conductivity; Methodology of the study; Results and discussion.

Presents a study which investigate the microstructure of solid state processed (bismuth, lead)-strontium-calcium-copper-oxygen ceramics using transmission electron microscopy techniques. Experimental details; Results and discussion; Conclusion.

Presents a study that developed a statistical model to examine the magnetization reversal of domain-wall nucleation controlled permanent magnets. Details of the model; Calculation of the hysteresis loop of the magnets using the model; Effect of demagnetizing field on the magnetization reversal of the magnets.

Presents a study that evaluated the effect of grain size and grain-size distribution on the intrinsic coercivity and the hysteresis loop of sintered iron-neodymium-boron magnets. Methodology; Influence of a bimodal grain size distribution on the hysteresis loop; Analysis of the scanning electron micrograph of the hard magnet.

Focuses on an experiment which investigated the imprint characteristics of integrated ferroelectric lead zirconate titanate based capacitors. What the evaluation of imprints requires; Indepth look at the experiment; Information on the results.

Discusses the concept of a temperature dependent domain stability map developed for tetragonal ferroelectrics grown on cubic substrates in an experimental context. Influence of then substrate lattice parameter on domain selection; Differential thermal expansion; Electrode geometry and applied fields.