One of the simplest methods for splitting water into H2 and O2 with solar energy entails the use of a particulate-type semiconductor photocatalyst. To harness solar energy efficiently, a new water-splitting photocatalyst that is active over a wider range of the visible spectrum has been developed. In particular, a complex perovskite-type oxynitride, LaMg(x)Ta(1-x)O(1+3x)N(2-3x)(x≥1/3), can be employed for overall water splitting at wavelengths of up to 600 nm. Two effective strategies for overall water splitting were developed. The first entails the compositional fine-tuning of a photocatalyst to adjust the bandgap energy and position by forming a series of LaMg(x)Ta(1-x)O(1+3x)N(2-3x) solid solutions. The second method is based on the surface coating of the photocatalyst with a layer of amorphous oxyhydroxide to control the surface redox reactions. By combining these two strategies, the degradation of the photocatalyst and the reverse reaction could be prevented, resulting in successful overall water splitting.

In scanning transmission electron microscopy (STEM), single atoms can be imaged by detecting electrons scattered through high angles using post-specimen, annular-type detectors. Recently, it has been shown that the atomic-scale electric field of both the positive atomic nuclei and the surrounding negative electrons within crystalline materials can be probed by atomic-resolution differential phase contrast STEM. Here we demonstrate the real-space imaging of the (projected) atomic electric field distribution inside single Au atoms, using sub-Å spatial resolution STEM combined with a high-speed segmented detector. We directly visualize that the electric field distribution (blurred by the sub-Å size electron probe) drastically changes within the single Au atom in a shape that relates to the spatial variation of total charge density within the atom. Atomic-resolution electric field mapping with single-atom sensitivity enables us to examine their detailed internal and boundary structures.

Advanced electron microscopy reveals a unique structural relaxation mechanism in a magnetic skyrmion domain boundary core.

Precise measurement and characterization of electrostatic potential structures and the concomitant electric fields at nanodimensions are essential to understand and control the properties of modern materials and devices. However, directly observing and measuring such local electric field information is still a major challenge in microscopy. Here, differential phase contrast imaging in scanning transmission electron microscopy with segmented type detector is used to image a p-n junction in a GaAs compound semiconductor. Differential phase contrast imaging is able to both clearly visualize and quantify the projected, built-in electric field in the p-n junction. The technique is further shown capable of sensitively detecting the electric field variations due to dopant concentration steps within both p-type and n-type regions. Through live differential phase contrast imaging, this technique can potentially be used to image the electromagnetic field structure of new materials and devices even under working conditions.

Multiferroic materials, which offer the possibility of manipulating the magnetic state by an electric field or vice versa, are of great current interest. However, single-phase materials with such cross-coupling properties at room temperature exist rarely in nature; new design of nano-engineered thin films with a strong magneto-electric coupling is a fundamental challenge. Here we demonstrate a robust room-temperature magneto-electric coupling in a bismuth-layer-structured ferroelectric Bi5Ti3FeO15 with high ferroelectric Curie temperature of ~1000 K. Bi5Ti3FeO15 thin films grown by pulsed laser deposition are single-phase layered perovskit with nearly (00l)-orientation. Room-temperature multiferroic behavior is demonstrated by a large modulation in magneto-polarization and magneto-dielectric responses. Local structural characterizations by transmission electron microscopy and Mössbauer spectroscopy reveal the existence of Fe-rich nanodomains, which cause a short-range magnetic ordering at ~620 K. In Bi5Ti3FeO15 with a stable ferroelectric order, the spin canting of magnetic-ion-based nanodomains via the Dzyaloshinskii-Moriya interaction might yield a robust magneto-electric coupling of ~400 mV/Oe·cm even at room temperature.