We have studied imprint mechanism of ferroelectric memory based on the oxygen-vacancy screening model. Interface charge density and offset bias for PZT resulted from the imprint were estimated as a function of effective depth for diffusion of oxygen vacancy based on this model. In order to understand microscopic dynamics during the imprint that might affect the interface charge density, molecular dynamics simulation (MD) was carried out. Diffusion length during the real imprint test for PZT was estimated based on the diffusion constant obtained from the MD simulation. By using the diffusion length, interface charge density and, in turn, offset bias was quantitatively estimated. Based on the quantitative analysis, it is found that the oxygen-vacancy screening model with microscopic dynamics obtained from the simulation explains well the imprint mechanism for PZT materials family.

Out-of-phase boundaries (OPBs), planar faults between regions of a crystal that are misaligned by a fraction of a unit cell dimension, occur frequently in materials of high structural anisotropy. Rarely observed in the bulk, OPBs frequently exist in epitaxial films of layered complex oxides, such as YBCO-type, Aurivillius, and Ruddlesden-Popper phases, and frequently propagate through the entire thickness of a film, due to their large offset and the improbability of opposite-sign OPB annihilation. OPBs have previously been demonstrated to have a significant impact upon properties, so it is important to understand their generation. These faults arise through the same few mechanisms in the various layered complex oxides.

An effort is made to unify the discussion of nucleation of these defects, common to layered oxide materials. OPBs can nucleate at the film-substrate interface (primary) via steric, chemical, or misfit mechanisms, or post-growth (secondary) through crystallographic shear during decomposition of volatile components. Examples of the mechanisms observed during high-resolution transmission electron microscopy (HRTEM) study of Aurivillius and Ruddlesden-Popper phases are presented. A method for estimating the relative OPB density in a film from correlation of x-ray diffraction (XRD) θ-2θ data with TEM information on OPBs is presented.

Lanthanum-modified lead titanate (PLT) ferroelectric thin films were fabricated by the RF magnetron sputtering system on Pt/Ti/SiO2/Si(100) substrates. The x-ray diffraction (XRD) patterns of the PLT films showed that the pure perovskite structure was formed in the PLT thin films. The Piezoresponse Force Microscopy (PFM) was used for determining the domain structure of these films. It was found that the 90 degree domain was the main domain structure of PLT thin films. It was found that the PLT films prepared by RF sputtering have relatively large pyroelectric coefficient γ=2.20×10-8C·(cm2·K)-1 and relatively high figures of merit for current responsivity, voltage responsivity and specific detectivity.

We report here the successful fabrication of BiFeO3 (BFO) isolated micron-sized structures by pulsed laser deposition. The islands have a relatively constant aspect ratio (height/lateral size) of 0.1-0.3. We present their local ferroelectric characterization, using piezoresponse force microscopy (PFM), showing that the micron-sized BFO islands exhibit a strong piezoresponse and have ferroelectric domains with lateral sizes down to the 100 nm range. We also present here the first results of Magnetostriction Force Microscopy experiments performed on these structures. On ferromagnetic samples this method reveals a piezomagnetic or magnetostriction contrast, associated with magnetic domains. In our case, we show that the contrast can be associated to the magnetoelectric effect.

Bismuth titanate (Bi4Ti3O12) is an electroceramic within the Aurivillius phase material with week ferroelectric memory. However, the partial substitution of Bi ion by a trivalent rare earth resulted in improved ferroelectric polarization. We synthesized Bi4-xSmxTi3O12 by a solution chemistry route and thin films were deposited by spin coating on Pt (Pt/TiO2/SiO2/Si) substrate. X-ray diffraction studies of the films showed a stoichiometric solid solution for the composition x ≤0.85. The films showed fatigue free ferroelectric polarization (Pr = 19.8 µC/cm2) for the composition x = 0.70. The films showed low leakage current at room temperature, showing the possibility of lead free ferroelectric devices.

This study is about new plasma deposition method fabricating piezoelectric films applied for actuators in MEMS devices.

In this study, a new method to achieve real information recording with a density of 1 Tbit/inch2 in ferroelectric data storage systems is proposed. In this system, data bits were written in the form of the polarization direction of nano domains. Local domain switching was carried out by applying a voltage pulse. A series of test writes revealed that the bit size varied according to the polarization direction of the bits in the immediate environment. Therefore, in order to keep the bit size constant (at 25.6 nm), the pulse amplitude required to create each individual bit was calculated as a function of the polarities of the surrounding data bits. As a result, real information storage at a density of 1 Tbit/inch2 was successfully achieved, with a low bit error rate of 1.8 × 10-2.

Mn-doped Bi3.25La0.75Ti3O12 (BLT) thin films were fabricated by depositing sol-gel solutions on Pt/Ti/SiO2/Si <100> substrates. The surface morphology and ferroelectric properties of Mn-doped BLT films depend upon the orientation of the films. Small amount of Mn-doping in BLT films influences the ferroelectric properties of the films, that is, it enhances the remanent polarization and reduces the coercive field. The 1% Mn-doped BLT films show enhanced remanent polarization and reduced the coercive field by about 22%. To the contrary, Mn-doping more than 1% decreases polarization gradually. Mn-doping significantly improves the fatigue resistance of BLT films. The reduced polarization in the 3.3% Mn-doped thin film recovers during switching cycles higher than 5 × 105. Under high switching field, the probability of field-assisted unpinning of domains is expected to be high and this may be the main cause for increase in polarization after 5 × 105 in the 3.3% Mn-doped BLT film.

Ion modification for various perovskite-based ferroelectric thin films using rare-earth cations was attempted for improving the electrical properties. Strategy for controlling the electrical properties is mainly based on two concepts, that is, (i) substituting the volatile cations such as Pb2+ and Bi3+, and (ii) controlling the crystal anisotropy of perovskite unit cell. In this study, the influences of ion-modification conditions (i.e., amount, species and occupying site of substituent cations) on the electrical properties of perovskite-based ferroelectric films fabricated by a chemical solution deposition were investigated. Substituting volatile cations in simple-perovskite oxides, such Pb2+ in Pb(Zr,Ti)O3 and Bi3+ in BiFeO3, for the rare-earth cations like La3+ and Nd3+ reduced the leakage current density of these films due to suppressing the metal and / or oxygen vacancies, as well as in layered-perovskite oxides, such as Bi4Ti3O12 films [i.e., strategy (i)]. Also, crystal anisotropy of perovskite-based oxides could controlled by varying the species and the occupying site of substituent cations [i.e., strategy (ii)]; for example, the crystal anisotropy of Pb(Zr,Ti)O3 lattice was elongated by Ti- and Zr-site (B-site) substitution using rare-earth cations whose ionic radii locate on the smaller part of rare-earth series (such as Y3+, Dy3+), that resulted in enhancing the spontaneous polarization. We concluded that the strategy for controlling the electrical property mentioned in this study would be applicable for a various kind of perovskite-based ferroelectric films.

Barium titanate thin films have been deposited on copper foils in the absence of interfacial layers via a chemical solution process. The dielectric – base metal stacks have been processed in reductive atmospheres such that substrate oxidation is avoided while allowing the perovskite film phase to crystallize. This accomplishment has facilitated the pursuit of a new embedded capacitor technology offering compatibility with polymer printed wiring boards and capacitance densities in excess of 2.5 µF/cm2. This represents a distinct improvement beyond conventional foil-based capacitor strategies. Finally, two critical phenomena will be discussed: (1) the effect of grain size on the dielectric properties of barium titanate thin films and (2) the effect of the B-site substituent Zr on the lattice, microstructure, and dielectric properties. Most importantly, high processing temperatures have allowed for microstructural and dielectric properties similar to well-prepared bulk ceramics, including average grain diameters greater than 0.1 µm, relative permittivities in excess of 2000, and coercive fields below 10 kV/cm. These properties will be discussed in the context of bulk ceramic and thin film reference data and with regard to integration into printed wiring boards.