This paper describes the recent development of surface activated bonding (SAB) and its bonding mechanism. The standard SAB takes full advantage of the activated surfaces created by Ar ion beam bombardment for room temperature bonding of various metals and semiconductor materials. A method of extending SAB has been developed for bonding glass and ionic materials as well as polymers. An example of bonding GaN and a diamond substrate was demonstrated to confirm the feasibility of an extended SAB that adopts a thin Si nano adhesion layer to activate the interface between Ga and C for room temperature bonding. The bonding showed the highest value of thermal barrier conductance. Finally, the concept of cryogenic bonding is also introduced.

Scanning transmission X-ray microscopy (STXM) is one of the powerful tools that enables chemical state imaging with a relatively high spatial resolution: several-tens of nm. A brief review on the principles and features of STXM is provided. STXM observation results on the molecular mixing state of an organic photovoltaic device and the magnetic domain structure of rare-earth permanent magnets are described.

All-solid-state Li-ion batteries are expected to be the next-generation energy storage device with high energy-density, safety, low cost, and a long lifetime. However, the high interfacial resistance of the Li-ion transfer at electrode/solid-electrolyte interfaces prevents the practical use of the batteries. Thus, it is essential to understand how electrochemical reactions occur at the interfaces. Here, we used electron holography and electron energy-loss spectroscopy (EELS) to visualize the local electric potential distribution and Li distribution at a metal-electrode/solid-electrolyte interface, which is an ionic space charge layer (SCL). The width of the ionic SCL was about 10 nm and its potential difference was 1.3 V. Also, we show the dynamics of Li-ions in a LiCoO₂ thin film electrode during charge - discharge reactions using EELS with a scanning transmission electron microscope.

Doping to control physical properties by adding small amounts of elements to a mother crystal is widely used in modern science. Photoelectron holography enables direct observation of the three-dimensional atomic arrangement of the dopant by observing the angular distribution of the photoelectrons emitted from the dopant. We report the results of applying this method to arsenic-doped silicon and phosphorus-doped diamonds. It was found that the dopant has multiple valence states and each valence had a different atomic arrangement. From this, information, the relationship between the atomic arrangement and the number of charge carriers and the behavior of the dopant during the crystal growth can be obtained.

In this paper, two characterization results based on multiphoton-excitation photoluminescence measurements are introduced. First, a classification of the threading dislocations in HVPE-grown GaN is performed. The screw dislocations had stronger non-radiative recombination properties than others, thus the dark lines had a stronger contrast. The mixed dislocations were propagated with a specific inclination angle from the c-axis. Next, simultaneous imaging of the three-dimensional growth process was performed and the behavior of threading dislocation propagation was observed. By constructing a three-dimensional image from the relative photoluminescence intensity of the near-band-edge emission to yellow luminescence, the non-c-plane growth region and the c-plane growth region could be identified, Thus, the complicated three-dimensional growth process and the propagation behavior of threading dislocations could be characterized.

Our urgent goal is to achieve a sustainable society where a healthy global environment and prosperous economic activity can coexist. For this purpose, we have to develop devices utilizing nanomaterials, such as 2D atomic layers. To maximize device performance, I have exploited operando x-ray spectromicroscopies that enable the nanoscopic elucidation of electronic structures of surfaces and interfaces of devices under operation. I have succeeded in applying these spectromicroscopies for the research and development of devices utilizing 2D atomic layers and AlGaN/GaN 2D electron systems, and contributed to designations that maximize device performance. Currently, I am implementing a novel method to quantitatively connect nanoscale surfaces and interface properties with device functions that appear macroscopically.

Recently, the word “edge computing” is often heard along with the word IoT. In this explanation, we will provide the background behind the emergence of “edge computing”, which is a key technology for realizing IoT, and the functions that it must have. Furthermore, by introducing the “My-IoT development platform” which is being developed as an example of future edge computing efforts, we will clarify the current IoT issues and describe future prospects.