Chalcogenide materials such as GeTe, Sb2Te3, Ge2Sb2Te5, compounds of sulfur, selenium, and tellurium, are characterized by a rapid and reversible phase transition. They have emerged as versatile candidates for advanced electronic and computing applications due to their unique optical and electrical properties. The potential of single-layer, multi-layer, and superlattice chalcogenides as the active materials in non-volatile memory (NVM) and artificial intelligence (AI) devices is shown in this review. Single-layer chalcogenides often offer exceptional scalability, fast speed, and nonvolatility, enabling them usable for NVM and synaptic devices. Multi-layer chalcogenides with stacked structures exhibit unique properties different from single-layer chalcogenides, allowing high performance such as low power and multilevel storage. Superlattice chalcogenides with alternating chalcogenide layers enable ultra-low power consumption of devices, in which only few of atom moves for the operation of devices. This review also gives some related research details. A comprehensive understanding of these studies provides insights into the design and application of chalcogenide-based devices, offering pathways for future research and innovation in memory and AI hardware.

Floating surface single-junction type photodiodes are mostly used in solar cell applications for simplicity and cost. On the other hand, pinned-surface and double-junction type photodiodes are used now in super high-performance image sensor applications. This paper first reviews the difference between the conventional floating-surface single-junction type photodiode and the pinned-surface double-junction type photodiode. The pinned-surface buried-channel P+PNPP+ double junction type photodiodes are very high-performance image sensors with no image lag and very high light sensitivity compared to conventional ones. The diode can be applied not only to image sensors but also to solar cells. In addition, this paper proposes a new AI robot vision chip in the modern 3DIC CMOS image sensor technology using this double junction type diode. So, the diode will be widely interested in process, device, and application researchers and engineers for image sensors and solar cells. A real-time AI smart robot vision chip is described as an example of application, which is composed of an array of N × N pinned-surface buried-channel P+PNPP+ double junction type photo diodes, N × N analog-data stream mask-and-match comparators, digital processing and SRAM cache buffer memory units, integrated in a 3-D multichip architecture. In the external power-off mode, the image sensor array of N × N pinned-surface buried-channel P+PNPP+ double junction type photo diodes also function as a solar cell unit for the AI self-energy robot vision chip.

The potassium sodium niobate (KxNa1−x)NbO3 (KNN) family with the perovskite structure is a technologically important lead-free piezoelectric material. This paper reviews the ferroelectric and structural phase transitions of KNN and related materials. The nature of end members, the physical properties, and phase transitions of simple alkali niobate materials MNbO3 (M=Li, Na, K, Rb, and Cs) are reviewed. The binary solid solution's phase diagram, KNN, is introduced concerning the morphotropic phase boundary (MPB). To understand the phase transitions near the MPB composition, the temperature dependences of lattice dynamical properties of KNN single crystals on optical modes and acoustic modes are reviewed by Raman and Brillouin scattering studies, respectively. Physical properties and phase transitions of KNN-based solid solutions were also reviewed.

Tactile technology is becoming increasingly important due to robotics applications and the use of the metaverse. However, there is few research on tactile technologies that can provide information on two-point discrimination thresholds at the human sensory level, and practical application has not progressed. This is due to the fact that the devices are complex and cannot be compactly mounted in key locations such as fingertips. This research aims to develop thin, flexible piezoelectric resin devices and put them into practical use. Here, it is important to miniaturize the drive circuits that drive such piezoelectric devices, so we developed a drive system that uses a piezoelectric driver IC that utilizes serial communication, and is capable of generating a wide range of tactile sensations, including multi-tone gradations.