Nanoscale Mn-doped BiFeO₃ (BFMO) films are prepared by chemical solution deposition on Pt/Ti/SiO₂/Si substrates. Nonpolar nonvolatile resistive switching has been observed in Pt/BFMO/Pt structure. Analysis of the current-voltage relationship demonstrates that the space-charge-limited current conduction controlled by the localized traps should be of great importance to the resistance switching. X-ray photoelectron spectroscopy results suggest that the coexistence of Fe²⁺ and Fe³⁺ can be ascribed to the relatively oxygen vacancies. According to defect chemistry, the valence variation between Fe²⁺ and Fe³⁺ determined by the neutralization/ionization of oxygen vacancies is supposed to play a crucial role in conductive filament-related nonpolar resistive switching.

A new iridium complex with a phenylphthalazine ligand has been prepared by an unexpected method and polymer light-emitting devices doped with the complex have been achieved with nearly 100% internal phosphorescence efficiency.

Ultrathin ferroelectric films are of increasing interests these years, owing to the need of device miniaturization and their wide spectrum of appealing properties. Recent advanced deposition methods and characterization techniques have largely broadened the scope of experimental researches of ultrathin ferroelectric films, pushing intensive property study and promising device applications. This review aims to cover state-of-the-art experimental works of ultrathin ferroelectric films, with a comprehensive survey of growth methods, characterization techniques, important phenomena and properties, as well as device applications. The strongest emphasis is on those aspects intimately related to the unique phenomena and physics of ultrathin ferroelectric films. Prospects and challenges of this field also have been highlighted.

Using density-functional theory (DFT) calculations, the formation energies, electron affinities and electronic levels of various intrinsic defects in bulk ${\text{LaAlO}}_3$ are investigated. Results give the atomic structures of charged interstitials, vacancies, Frenkel pairs, antisite defects, and Schottky defects, respectively. It is found that the formation energies of O vacancy are the lowest in the reducing conditions. In contrast, the La vacancy $V_{\text{La}}$ is more favorable in formation energy as the O chemical potential increasing. Moreover, by considering the defect levels of ${\text{LaAlO}}_3$ with respect to the silicon conduction bands, the effects of the electron and hole trapping in real devices are also simulated. Our results show that the paired charged $V_{\text{O}}$, which lies in the middle of the silicon band gap, should be the key problematic defect. The deep defect level of $V_{\text{O}}$ can induce a large-tunneling-leakage current and cause instability in the device performance. These predictions provide rich defect structures in ${\text{LaAlO}}_3$ and useful information for the microelectronic designs.

Vortex domain patterns in low-dimensional ferroelectrics and multiferroics have been extensively studied with the aim of developing nanoscale functional devices. However, control of the vortex domain structure has not been investigated systematically. Taking into account effects of inhomogeneous electromechanical fields, ambient temperature, surface and size, we demonstrate significant influence of mechanical load on the vortex domain structure in ferroelectric nanoplatelets. Our analysis shows that the size and number of dipole vortices can be controlled by mechanical load, and yields rich temperature-stress (T-S) phase diagrams. Simulations also reveal that transformations between “vortex states” induced by the mechanical load are possible, which is totally different from the conventional way controlled on the vortex domain by the electric field. These results are relevant to application of vortex domain structures in ferroelectric nanodevices, and suggest a novel route to applications including memories, mechanical sensors and transducers.

Ferroelectric vortex domain structure which exists in low-dimensional ferroelectrics is being intensively researched for future applications in functional nanodevices. Here we demonstrate that adjusting surface charge screening in combination with temperature can provide an efficient way to gain control of vortex domain structure in ferroelectric nanodot. Systematical simulating experiments have been conducted to reveal the stability and evolution mechanisms of domain structure in ferroelectric nanodot under various conditions, including processes of cooling-down/heating-up under different surface charge screening conditions and increasing/decreasing surface charge screening at different temperatures. Fruitful phase diagrams as functions of surface screening and temperature are presented, together with evolution paths of various domain patterns. Calculations discover up to 25 different kinds of domain patterns and 22 typical evolution paths of phase transitions. The fruitful controllability of vortex domain structure by surface charge screening in combination with temperature should shed light on prospective nanodevice applications of low-dimensional ferroelectric nanostructures.