Achieving Boosted Thermoelectric Power Factor of MoS through Selective Charged-Impurity-Free Doping.

Ultrathin two-dimensional (2D) transition metal dichalcogenides (TMDs) exhibit unique band structures, allowing promising thermoelectric properties. Achieving a high power factor () for thermoelectric generators (TEGs) requires optimizing both the Seebeck coefficient () and electrical conductivity (). Conventional surface charge-transfer doping can be a solution to enhance by introducing additional electrons.

Low-Frequency Noise Spectroscopy for Navigating Geometrically Varying Strain Effects in HfO Ferroelectric FETs.

Strain engineering has been widely employed to control and enhance the ferroelectric properties of hafnium oxide (HfO₂)-based thin films. While previous studies focused on the influence of the strain in simple metal-ferroelectric-metal structures, the integration of strain-induced ferroelectricity into field-effect transistors (FETs) requires consideration of geometrical factors, such as the interfaces between the channel and source/drain contacts, as well as device dimension. Here, we demonstrate strain effects in HfO₂-based ferroelectric FETs (FeFETs) with poly-Si channels via low-frequency noise (LFN) spectroscopy.

Stable Supercapacity of Binder-Free TiO(B) Epitaxial Electrodes for All-Solid-State Nanobatteries.

Owing to its pseudocapacitive, unidimensional, rapid ion channels, TiO(B) is a promising material for application to battery electrodes. In this study, we align these channels by epitaxially growing TiO(B) films with the assistance of an isostructural VO(B) template layer. In a liquid electrolyte, binder-free TiO(B) epitaxial electrodes exhibit a supercapacity near the theoretical value of 335 mA h g and an excellent charge-discharge reproducibility for ≥200 cycles, which outperform those of other TiO(B) nanostructures.

Inhibiting collective cation migration in Li-rich cathode materials as a strategy to mitigate voltage hysteresis.

Lithium-rich cathodes are promising energy storage materials due to their high energy densities. However, voltage hysteresis, which is generally associated with transition metal migration, limits their energy efficiency and implementation in practical devices. Here we reveal that voltage hysteresis is related to the collective migration of metal ions, and that isolating the migration events from each other by creating partial disorder can create high-capacity reversible cathode materials, even when migrating transition metal ions are present.

Exsolution of Ru Nanoparticles on BaCe Y O Modifying Geometry and Electronic Structure of Ru for Ammonia Synthesis Reaction Under Mild Conditions.

Green ammonia is an efficient, carbon-free energy carrier and storage medium. The ammonia synthesis using green hydrogen requires an active catalyst that operates under mild conditions. The catalytic activity can be promoted by controlling the geometry and electronic structure of the active species.

Unraveling the Origin and Mechanism of Nanofilament Formation in Polycrystalline SrTiO Resistive Switching Memories.

Three central themes in the study of the phenomenon of resistive switching are the nature of the conducting phase, why it forms, and how it forms. In this study, the answers to all three questions are provided by performing switching experiments in situ in a transmission electron microscope on thin films of the model system polycrystalline SrTiO . On the basis of high-resolution transmission electron microscopy, electron-energy-loss spectroscopy and in situ current-voltage measurements, the conducting phase is identified to be SrTi O .

Hidden structural and chemical order controls lithium transport in cation-disordered oxides for rechargeable batteries.

Structure plays a vital role in determining materials properties. In lithium ion cathode materials, the crystal structure defines the dimensionality and connectivity of interstitial sites, thus determining lithium ion diffusion kinetics. In most conventional cathode materials that are well-ordered, the average structure as seen in diffraction dictates the lithium ion diffusion pathways.

Reversible Mn/Mn double redox in lithium-excess cathode materials.

There is an urgent need for low-cost, resource-friendly, high-energy-density cathode materials for lithium-ion batteries to satisfy the rapidly increasing need for electrical energy storage. To replace the nickel and cobalt, which are limited resources and are associated with safety problems, in current lithium-ion batteries, high-capacity cathodes based on manganese would be particularly desirable owing to the low cost and high abundance of the metal, and the intrinsic stability of the Mn oxidation state. Here we present a strategy of combining high-valent cations and the partial substitution of fluorine for oxygen in a disordered-rocksalt structure to incorporate the reversible Mn/Mn double redox couple into lithium-excess cathode materials.

Mitigating oxygen loss to improve the cycling performance of high capacity cation-disordered cathode materials.

Recent progress in the understanding of percolation theory points to cation-disordered lithium-excess transition metal oxides as high-capacity lithium-ion cathode materials. Nevertheless, the oxygen redox processes required for these materials to deliver high capacity can trigger oxygen loss, which leads to the formation of resistive surface layers on the cathode particles. We demonstrate here that, somewhat surprisingly, fluorine can be incorporated into the bulk of disordered lithium nickel titanium molybdenum oxides using a standard solid-state method to increase the nickel content, and that this compositional modification is very effective in reducing oxygen loss, improving energy density, average voltage, and rate performance.

Epitaxial Brownmillerite Oxide Thin Films for Reliable Switching Memory.

Resistive switching memory, which is mostly based on polycrystalline thin films, suffers from wide distributions in switching parameters-including set voltage, reset voltage, and resistance-in their low- and high-resistance states. One of the most commonly used methods to overcome this limitation is to introduce inhomogeneity. By contrast, in this paper, we obtained uniform resistive switching parameters and sufficiently low forming voltage by maximizing the uniformity of an epitaxial thin film.

Atomic structure of conducting nanofilaments in TiO2 resistive switching memory.

Resistance switching in metal oxides could form the basis for next-generation non-volatile memory. It has been argued that the current in the high-conductivity state of several technologically relevant oxide materials flows through localized filaments, but these filaments have been characterized only indirectly, limiting our understanding of the switching mechanism. Here, we use high-resolution transmission electron microscopy to probe directly the nanofilaments in a Pt/TiO(2)/Pt system during resistive switching.