Japanese company Toshiba has invented and developed NAND Flash Memory, which has been widely used for a smartphone such as iPhone, USB memory, SD card, and SSD. NAND Flash Memory is compact, lightweight, quiet, impact resistant and capable to retain data regardless of whether the power is on or off. Unless NAND Flash Memory was invented, the widespread of personal computers and smartphones was delayed, and hampered the transition to a digital society. Fortunately, a research team of just 10 people at TOSHIBA invented the Flash Memory in the 1980s. The market scale in 2022 has now reached 10 trillion yen, and we cannot imagine a world without it.

Simple rare earth oxides are usually sesquioxides with stable trivalent rare earth ions, exhibiting highly insulating state. On the other hand, several rare earth monoxides with metastable divalent rare earth ions have been synthesized under high pressure only in 1980s, except for chemically stable EuO and YbO. Recently, we found that the rare earth monoxides can be synthesized by using thin film epitaxy. As a result, it is possible to obtain their first single crystalline or new solid phase substances, enabling to unveil their fundamental properties. In this article, we review recent progress on the synthesis and properties of rare earth monoxides.

We have been pioneering “multicrystalline informatics” that links experimental, theoretical, computational, and data science to establish universal guidelines for improving the performance of multicrystalline materials, aiming to innovate research methods for materials development using multicrystalline silicon as a model material. In this paper, we describe the research base that has been established and the new knowledge on the mechanism of dislocation cluster generation that has been obtained through their fusion and integration.

Semiconducting silicide BaSi₂ is an indirect band-gap semiconductor composed of earth-abundant elements with a forbidden bandwidth of about 1.3 eV. It has a large optical absorption coefficient equivalent to CuInS₂, and its conductivity type and carrier density can be controlled by impurity doping using group 13 and 15 elements. In this article, an approach to thin-film solar cells on glass substrates is introduced, utilizing the knowledge gained from epitaxial films on Si substrates.

Lithium-ion batteries (LIBs) are indispensable energy storage for our daily lives, but from the viewpoint of safety use, all-solid-state batteries have been promoted. Liquid-type LIBs which currently use have excellent cost performance due to optimization of the manufacturing process and other factors. In order to use all-solid-state batteries instead of liquid-type LIBs, various advantages are absolutely necessary. In this paper, I would like to propose all-solid-state batteries that can be handled in air condition and do not require strict dewpoint control, developed from a completely different perspective from conventional battery production.

Application of strain to materials is a promising method for probing and controlling physical prosperities from their strain responses. This article reviews the fundamental principles and experimental methods for strain control, which have made significant progress by using piezo-electric devices.