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The atomic switches have attracted wide attention owing to their applications in nonvolatile electric devices. The atomic switch is operated by the formation and dissipation of a metallic filament inside a metal sulfide film, which is controlled by a solid electrochemical reaction. Although the metallic filament is considered to consist of metal atoms, the chemical species of the metallic filament are difficult to be identified due to challenges in observing the metallic filament inside the solid. In this study, we report the investigation on the metallic filament in the atomic switch with metal sulfide based on point-contact spectroscopy (PCS). By cooling the atomic switch, the switch voltage increased to 1 V, which allowed for the PCS measurement. The PCS revealed that the metallic filament was composed of Ag atoms in the case of the Pt/Ag2S/Ag atomic switch. We applied this technique to the Pt/Cu2S/Ag and Pt/Ag2S/Cu atomic switches to uncover the formation process of the metallic filament. In both atomic switches, the chemical species of the metallic filament were Ag. The metal atoms were supplied from both the metal electrode and the sulfide layer.

Herein we report the manipulation of perpendicular magnetic anisotropy (PMA), a very important technique for spintronics devices, which is achieved in an all-solid-state redox (reduction/oxidation) device. The device consisted of NiCo2O4(NCO) thin film with a c-axis orientation and a proton-conducting polymer (Nafion). The PMA of NCO can be manipulated in situ with low voltage (V= 0.7 V) due to the utilization of a proton-conducting solid electrolyte. The magnetic anisotropy variation was quantitatively evaluated by an anomalous Hall measurement. The magnetic anisotropy field of the NCO thin film was successfully manipulated in the range of 5%, although the rotation of the easy axis of magnetization was not observed. This modulation is attributed to the strain and electronic configuration variation by proton insertion. This manipulation method for PMA with the solid electrolyte enables a variety of reservoir states and contributes to lower power consumption and high-precision machine learning.

The construction of an electronic‐conductor/ionic‐conductor heterojunction in a well‐defined nanostructure is the basis of studying interfacial and bulk transport and the reactions of ions and electrons at the nanoscale level. An ionic‐conductor/metal (AgI/Ag) heterostructured nanowire array is easily fabricated by a template‐confined, step‐electrochemical technique. The structural and morphological evolution of the AgI/Ag heterostructure before and after its release from the anodic aluminum oxide (AAO) membrane is characterized by scanning electron microscopy, X‐ray diffraction, and optical spectroscopy. The structural disordering of released AgI is suggested by the appearance of a broad photoluminescence emission band at longer wavelengths and a short‐range‐order‐like Raman peak. The ionic conductivity of the AgI nanowire embedded inside the insulating AAO membrane is measured as being on the order of 10–3S cm–1, which is an enhancement by two to three orders of magnitude compared with that of bulk polycrystalline AgI at room temperature. This electrochemical method could be useful in fabricating other pure and mixed ionic conductors in heterojunction nanostructures.

Evolution of the domain shape during switching in electric field in congruent and stoichiometric lithium tantalate single crystals has been investigated both experimentally and by computer simulation. Domain patterns were observed using optical microscope. It was shown that typical domain shape is triangular for congruent lithium tantalate and hexagonal for stoichiometric one. The domain shape changes during cyclic switching. The kinetic nature of the domain shape has been proposed. The variety of domain shapes from triangular to hexagonal through intermediate shapes has been studied by computer simulation of the isolated domain growth. We report the first evidence of formation of the ordered domain structure in stoichiometric lithium tantalate with artificial dielectric layer.

LiNbO3precursor gels with a variety of molecular structures were prepared by the sol-gel method by changing the amount of added water and other conditions of synthesis. The molecular structures, as well as the thermal behaviour of the amorphous precursors, were studied by Raman spectroscopic analysis and differential thermal analysis-thermogravimetry in order to determine the influence of the structures on the resulting LiNbO3formation. The crystallization to LiNbO3by the combustion heat of the residual unhydrolysed alkyls was observed at ∼ 300 °C for the homogeneous precursors prepared from a double alkoxide (LiNb(OC2H5)6) without added water, but the LiNbO3formed had low crystallinity. When using the hydrolysed double alkoxide, the synthesized precursors transformed to LiNbO3at ∼ 480 °C after the structural relaxation. This temperature can be assigned to the real crystallization point. Indeed the unhydrolysed double alkoxide is necessary to prepare the high-quality LiNbO3films, and heat treatment above ∼ 500°C is required to obtain good crystallinity. Even for the inhomogeneous precursors prepared from LiOC2H5and NbO(C2H5)5, lithium ion diffusion and the structural relaxation occur, to form the uniform molecular structures from 300–400 °C.

TiO2 precursors were prepared by the sol-gel method using titanium tetraisopropoxide. The effects of water and hydrochloric acid addition for the hydrolysis and polymerization reaction on the crystal lattice or the molecular structure, and on the crystallization behaviour of prepared precursors, were examined by using Raman, and infrared spectroscopy, X-ray diffraction, DTA-TG and carbon analysis. The quantity of unhydrolysed alkyls in precursors decreased with increasing amounts of H2O and HCl addition, but the alkyls always remained. Raman spectroscopy revealed that the molecular structure of prepared amorphous precursors resembled that of the anatase phase with increased H2O and HCl addition. On the crystallization process of these precursors, the ratio of anatase formed at 310 °C was influenced by residual unhydrolysed alkyls. Steric hindrance by the residual alkyls preventing crystallization to crystalline anatase was observed, and there was estimated to be 2.5 mol of octahedral coordination of Ti-O per 1 mol of residual alkyls. It is noted that crystallization of the anatase phase and the transformation from anatase to the rutile phase were also observed on long-term ageing of precursors at room temperature.