Kazunori Nishio

We demonstrate the selective fabrication of Ruddlesden-Popper (RP) type SrIrO3, Sr3Ir2O7, and Sr2IrO4 epitaxial thin films from a single SrIrO3 target using pulsed laser deposition (PLD). We identified that the growth conditions stabilizing each phase directly map onto the phase diagram expected from thermodynamic equilibria. This approach allows precise cation stoichiometry control as evidenced by the stabilization of single phase Sr3Ir2O7 for the first time, overcoming the close thermodynamic

Rutile TiO2 is a promising electrode material for Li-ion secondary batteries. It has been theoretically predicted that rutile TiO2 exhibits anisotropy in the Li-ion diffusion coefficients, which may impact the battery performance. Consequently, to improve the battery performance, the effect of the anisotropy of Li-ion diffusion on battery performance must be clarified. Here, we quantitatively discuss the influence of the crystal orientation of rutile TiO2 on battery performance, in particular, o

We report the low resistance observed at the interface of LiNi1/3Mn1/3Co1/3O2 (NMC) and Li3PO4. First, we show the deposition of high-quality single-phase NMC (001) epitaxial thin films on Al2O3 (0001) substrates using pulsed laser deposition. Controlling the oxidation states of the three transition metals in NMC films is crucial for stable battery operation. However, in general, it is very difficult to simultaneously control the oxidation states of three elements in vacuum deposition processes.

Understanding the origin of the resistance at the interfaces of a solid electrolyte and electrode material is crucial for the design of high-performance all-solid-state lithium batteries. In particular, it is of considerable importance to quantitatively study the impact of the crystal orientations of electrodes on the interface resistance. However, the investigation of the properties of buried interfaces has been challenging because conventional studies are based on granular samples. In this wor

Low interfacial resistance between the solid sulfide electrolyte and the electrode is critical for developing all-solid-state Li batteries; however, the origin of interfacial resistance has not been quantitatively reported in the literature. This study reports the resistance values across the interface between an amorphous Li₃PS₄ solid electrolyte and a LiCoO₂(001) epitaxial thin film electrode in a thin-film Li battery model. High interfacial resistance is obser

We investigate feedback control of linear quantum systems subject to feedback-loop time delays. In particular, we examine the relation between the potentially achievable control performance and the time delays and provide theoretical guidelines for the future experimental setup in two physical systems, which are typical in this research field. The evaluation criterion for the analysis is given by the optimal control performance formula, the derivation of which is from the classical control theor

High-entropy oxides are emerging materials with unique functionalities. However, while various bulk-type high-entropy oxides have been developed, limited research has been pursued for high-entropy oxide thin films. In this paper, we report the synthesis of LiCr1/6Mn1/6Fe1/6Co1/6Ni1/6Cu1/6O2 epitaxial thin films with a layered rocksalt structure via the pulsed laser deposition technique. We obtained a single-phase epitaxial thin film by tuning the laser fluence and substrate temperature. In addit

Understanding electronic and ionic transport across interfaces is crucial for designing high-performance electric devices. The adjustment of work functions is critical for band alignment at the interfaces of metals and semiconductors. However, the electronic structures at the interfaces of metals and mixed conductors, which conduct both electrons and ions, remain poorly understood. This study reveals that a Schottky barrier is present at the interface of the Nb-doped SrTiO3 metal and a LiCoO2 mi

Here we demonstrate a high rate capability of all-solid-state lithium batteries using quasi-solid-state electrolytes containing an ionic liquid. We fabricated solid-state electrolyte using an ionic liquid: 1 mol l −1 lithium bis(fluorosulfonyl) imide dissolved 1-Ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (LiFSI/EMI-FSI) and fumed silica nanoparticles with a variety of volume fractions. The fabricated freestanding film with 85% volume fraction of LiFSI/EMI-FSI exhibited an ionic conductiv

We show that by delta doping a deep depletion layer at a SrTiO3/CaHfO3 interface with La, it is possible to achieve a separation of physical dopants from the current transport layer in SrTiO3. This allows us to construct an epitaxial top-gate field-effect transistor that can switch a channel with a physical dopant density of ∼1014 cm−2 between insulating and metallic states with a finite threshold shift and without carrier mobility degradation at low temperature.