Ferroelectricity in fluorite-structured ferroelectrics such as HfO2 and ZrO2 has been attracting increasing interest since its first publication in 2011. Fluorite-structured ferroelectrics are considered to be promising for semiconductor devices because of their compatibility with the complementary metal–oxide–semiconductor technology and scalability for highly dense information storage. The research on fluorite-structured ferroelectrics during the first decade of their conceptualization has been mainly focused on elucidating the origin of their ferroelectricity and improving the performance of electronic devices based on such ferroelectrics. Furthermore, as is known, to achieve optimal performance, the emerging biomimicking electronic devices as well as conventional semiconductor devices based on the classical von Neumann architecture require high operating speed, sufficient reliability, and multilevel data storage. Nanoscale electronic devices with fluorite-structured ferroelectrics serve as candidates for these device systems and, thus, have been intensively studied primarily because in ferroelectric materials the switching speed, reliability, and multilevel polarizability are known to be strongly correlated with the domains and domain dynamics. Although there have been important theoretical and experimental studies related to domains and domain dynamics in fluorite-structured ferroelectrics, they are yet to be comprehensively reviewed. Therefore, to provide a strong foundation for research in this field, herein, domains, domain dynamics, and emerging applications, particularly in neuromorphic computing, of fluorite-structured ferroelectrics are comprehensively reviewed based on the existing literature.

Ferroelectric materials are known to be ideal materials for nonvolatile memory devices, owing to their two electrically switchable spontaneous polarization states. However, difficulties in scaling down devices with ferroelectric materials have hindered their practical applications and research. The discovery of ferroelectricity in fluorite-structured ferroelectrics has revived research on semiconductor devices based on ferroelectrics. With their scalability and established fabrication techniques, the performance of nanoscale electronic devices with fluorite-structured ferroelectrics is being rapidly developed. However, the fundamental physics behind the superior ferroelectricity is yet to be elucidated. From this Perspective, the status of research on fluorite-structured ferroelectrics and state-of-the-art semiconductor devices based on them are comprehensively reviewed. In particular, the fundamental physics of fluorite-structured oxides is critically reviewed based on a newly developed theory as well as on the classical theory on ferroelectrics. A perspective on the establishment of emerging semiconductor devices based on fluorite-structured ferroelectrics is provided from the viewpoint of materials science and engineering.

A continuous exponential rise has been observed in the storage and processing of the data that may not curtail in the foreseeable future. The required data processing speed and power consumption are restricted by the buses between the logic and memory devices that are characteristic of the von Neumann computing architecture. Bio-mimicking neuromorphic computing has garnered considerable academic and industrial interest to resolve these challenges.Additionally, devices based on emerging nonvolatile memories capable of mimicking the behaviors of synapses and neurons, which are the main elements in biological computing systems (brains), are attracting significant interest from the device community. With the discovery of ferroelectricity in fluorite-structured oxides, such as HfO 2 and ZrO 2 , which are compatible with the state-of-the-art complementary-metal-oxide-semiconductor processes, ferroelectric devices have rapidly evolved as the main direction of these research and development activities. Fundamental science related to fluorite-structured ferroelectrics has been intensively studied over the last decade. At present, the focus is gradually moving to practical applications, including neuromorphic computing and advanced classical processing or memory units in the conventional von Neumann architecture. However, despite its rapid development, the wealth of recent progress in neuromorphic computing devices based on fluorite-structured ferroelectrics has not been reviewed and systemized. This progress report comprehensively reviews and systemizes the recent progress in artificial synaptic and spiking neuron devices for neuromorphic computing based on fluorite-structured ferroelectrics.

Over the last few decades, the research on ferroelectric memories has been limited due to their dimensional scalability and incompatibility with complementary metal‐oxide‐semiconductor (CMOS) technology. The discovery of ferroelectricity in fluorite‐structured oxides revived interest in the research on ferroelectric memories, by inducing nanoscale nonvolatility in state‐of‐the‐art gate insulators by minute doping and thermal treatment. The potential of this approach has been demonstrated by the fabrication of sub‐30 nm electronic devices. Nonetheless, to realize practical applications, various technical limitations, such as insufficient reliability including endurance, retention, and imprint, as well as large device‐to‐device‐variation, require urgent solutions. Furthermore, such limitations should be considered based on targeting devices as well as applications. Various types of ferroelectric memories including ferroelectric random‐access‐memory, ferroelectric field‐effect‐transistor, and ferroelectric tunnel junction should be considered for classical nonvolatile memories as well as emerging neuromorphic computing and processing‐in‐memory. Therefore, from the viewpoint of materials science, this review covers the recent research focusing on ferroelectric memories from the history of conventional approaches to future prospects.

An antiferroelectric Mo/Hf0.3Zr0.7O2/SIOx/Si capacitor was engineered using the direct scavenging effect of a sputtered Ti sacrificial layer. Charge trapping could be mitigated with the oxidized TiO2 layer, and the endurance...

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Ferroelectricity has been increasingly applied to develop fluorite-structured oxides since its discovery in 2011. Unlike conventional ferroelectric materials, these materials are compatible with complementary metal oxide semiconductor technology with established fabrication techniques. Early stage research has focused on enhancing the ferroelectricity in solid solution films for nonvolatile data storage. Recently, engineering strategies, such as those that entail the use of morphotropic phase boundaries to achieve high permittivity and develop artificial structures such as nanolaminates/superlattices, have been suggested to enhance ferroelectricity/antiferroelectricity; such strategies have the potential to provide new pathways for advanced nanoelectronics. Furthermore, the dielectric constant, remanent polarization, and processing window applied in these strategies yield more desirable outcomes than the solid solutions. Such strategies are also believed to be applicable to the design of cell capacitors for dynamic and ferroelectric random-access memory technology. However, a comprehensive review of these ferroelectricity-related engineering strategies has not yet been reported. Thus, recently developed engineering strategies for fluorite-structured ferroelectrics are reviewed in this paper.

The aim of this study was to compare the painting portraits of beautiful women, femme fatales, and artists' mothers using anthropometry.Portraits of each theme were selected in modern novels, essays and picture books, and categorized portraits. A total of 52 samples were collected, including 20 beautiful women, 20 femme fatales, and 12 artists' mothers. In 5 persons, 17 anthropometric ratios including the alae-alae/zygion-zygion ratio were compared in a 15-degree oblique view and in anteroposterior view photographs, and they were proved to not differ significantly. To distinguish oblique portraits less than 15 degrees, we measured the exocanthion-stomion-exocanthion (ESE) angle in photographs of 5 volunteers. The mean ± SD of the ESE angle was 64.52 ± 4.87 in the 15-degree angle view and 57.68 ± 54.09 in the 30-degree angle view. Thereafter, if the ESE angle was greater than 65 degrees, we considered the portrait to have less than a 15-degree angle and included it in the samples.The ratio did not differ significantly in 11 anthropometric proportions. However, the remaining 5 proportions were statistically significant. Beautiful women had wider noses (85% of the endocanthion-endocanthion width) than those of the femme fatale group (77%). Lips in the beautiful woman group are nicer and thicker (36% of lip's width) compared with the artists' mother group (27%). Femme fatales were relatively similar to beautiful women such as those women with nice and thick lips. However, the femme fatale group had an attractive midface ratio (36% of the total face height) that has been mentioned in the older literature, and the noses of the femme fatale group were narrower and sharper (77% of the endocanthion-endocanthion width) than those of the beautiful women (85%). The artists' mother group has a relatively narrower upper face (29% of the total face height) and thinner lips (27% of the lip width) compared with the other 2 groups (36%).Proportions from works of art are more ideal and attractive than clinically measured proportions. The ideal ratios measured from historical portraits might be useful in planning facial surgeries.