Resistive switching in transition metal oxides

A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

Perspective on the Development of Lead-free Piezoceramics

Potassium-sodium niobate lead-free piezoelectric materials: past, present, and future of phase boundaries.

This review article attempts to provide a comprehensive review of the recent progress in the so-called resistive random access memories (RRAMs) First, a brief introduction is presented to describe the construction and development of RRAMs, their potential for broad applications in the fields of nonvolatile memory, unconventional computing and logic devices, and the focus of research concerning RRAMs over the past decade Second, both inorganic and organic materials used in RRAMs are summarized, and their respective advantages and shortcomings are discussed Third, the important switching mechanisms are discussed in depth and are classified into ion migration, charge trapping/de-trapping, thermochemical reaction, exclusive mechanisms in inorganics, and exclusive mechanisms in organics Fourth, attention is given to the application of RRAMs for data storage, including their current performance, methods for performance enhancement, sneak-path issue and possible solutions, and demonstrations of 2-D and 3-D crossbar arrays Fifth, prospective applications of RRAMs in unconventional computing, as well as logic devices and multi-functionalization of RRAMs, are comprehensively summarized and thoroughly discussed The present review article ends with a short discussion concerning the challenges and future prospects of the RRAMs

Recent progress in resistive random access memories: Materials, switching mechanisms, and performance

https://www.bc.edu/content/dam/files/schools/cas_sites/physics/pdf/Ren/250_Nano_Energy_1%2C_42-56_2012.pdf

Recent advances in thermoelectric nanocomposites

Ferroelectric (Pb,La)(Zr,Ti)O3 (PLZT) thin films have been epitaxially grown on the c plane of sapphire by rf‐planar magnetron sputtering. The sputtering conditions were investigated to obtain epitaxial and transparent films. Dielectric, piezoelectric, and electro‐optic properties of the films were measured. Piezoelectricity of the PLZT(28/0/100) film was confirmed and was as strong as that of BaTiO3. Excellent quadratic electro‐optic effects for PLZT(28/0/100) and PLZT(9/65/35) films and a linear electro‐optic effect for PLZT(21/0/100) film were observed at 0.633‐μm wavelength. Epitaxial PLZT thin film on sapphire is presently the most promising material for new functional devices.

Ferroelectric (Pb,La)(Zr,Ti)O3 epitaxial thin films on sapphire grown by rf-planar magnetron sputtering

The electronic conduction through a ${\mathrm{Pr}}_{0.7}{\mathrm{Ca}}_{0.3}\mathrm{Mn}{\mathrm{O}}_{3}$ thin film is investigated by measurements using dc and pulsed biases. Semiconducting ${\mathrm{Pr}}_{0.7}{\mathrm{Ca}}_{0.3}\mathrm{Mn}{\mathrm{O}}_{3}$ films sandwiched by electrodes show both hysteretic and asymmetric behaviors in current-voltage characteristics. The observed conduction characteristics exhibit the space-charge-limited-current effect, and the hysteretic behavior can be ascribed to a carrier trapping and detrapping of the trap sites in the manganite. The hysteresis induces a colossal electroresistance (CER) of more than 5000% at room temperature. The CER ratio is independent of the duration time of pulses from an infinite (dc) down to $150\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$, indicating that the carrier filling of all the traps can be completed within a short time.

Colossal electroresistance of a Pr 0.7 Ca 0.3 Mn O 3 thin film at room temperature

PLZT thin-film channel waveguides have been successfully formed in ridges by an ion-beam etching process. The electrooptic Kerr coefficients of the waveguides have been newly obtained. We have determined that the electrooptic coefficients 
R11′ and 
R12′ were 0.1–0.2 × 10−16 (m/V)2 and 0.01 × 10−16 (m/V)2, respectively, by Mach-Zehnder interferometric measurement. It was confirmed that PLZT channel waveguides were much more efficient than conventional Ti-diffused LiNbO3 waveguides.

PLZT thin-film waveguides

We have established the low‐temperature process for the preparation of high Tc superconducting films by rf magnetron sputtering. The films were deposited at a temperature (650 °C) lower than the tetragonal‐orthorhombic transition point with sufficient crystallizing and oxidizing conditions. The as‐deposited Er‐Ba‐Cu‐O film on MgO exhibited a sharp superconductive transition with zero resistance at 86 K. This process prevented diffusion at the film and substrate interface and reduced the porous structure in the films.

Low‐temperature process for the preparation of high Tc superconducting thin films

Epitaxial (Pb, La)(Zr, Ti)O3 thin films were grown successfully on (0001) sapphire substrates at below 600 °C. High quadratic electro‐optic coefficient of 0.8×10−16 (m/V)2 was also obtained at 6328 A. The rf planar magnetron sputtering process improved the quality of the film, which will be suitable for thin‐film integrated optic devices.

Hideaki Adachi

Papers

Ferroelectric (Pb,La)(Zr,Ti)O3 epitaxial thin films on sapphire grown by rf-planar magnetron sputtering

Colossal electroresistance of a Pr 0.7 Ca 0.3 Mn O 3 thin film at room temperature

PLZT thin-film waveguides

Low‐temperature process for the preparation of high Tc superconducting thin films

Electro‐optic effects of (Pb, La)(Zr, Ti)O3 thin films prepared by rf planar magnetron sputtering