Physica Status Solidi (A) Applications and Materials Science

Rechargeable all‐solid‐state lithium Li‐ion batteries (AS‐LIBs) are attractive power sources for electrochemical applications; due to their potentiality in improving safety and stability over conventional batteries with liquid electrolytes. AS‐LIBs require a Li‐fast ion conductor (FIC) as the solid electrolyte. Finding a solid electrolyte with high ionic conductivity and compatibility with other battery components is a key factor in building high performance AS‐LIBs. There have been numerous studies, e.g., on lithium rich sulfide glasses as solid electrolytes. However, the limited current density remains a major obstacle in developing competitive batteries based on the known solid electrolytes. Here we prepare argyrodite‐type Li₆PS₅X (X = Cl, Br, I) using mechanical milling followed by annealing. XRD characterization reveals the formation and growth of Li₆PS₅X crystals in samples under varying annealing conditions. For Li₆PS₅Cl an ionic conductivity of the order of 10⁻⁴ S/cm is reached at room temperature, which is close to the Li mobility in conventional liquid electrolytes (LiPF₆ in various carbonates) and well suitable for AS‐LIBs.

Tin monoxide (SnO) is a stable p‐type oxide semiconductor. This paper reports electrical properties, electronic structures, and thin‐film transistors (TFTs) of SnO. Epitaxial films were fabricated by pulsed laser deposition. The Hall mobility and the hole density of the epitaxial films were 2.4 cm² V⁻¹ s⁻¹ and 2.5 × 10¹⁷, respectively. X‐ray photoelectron spectroscopy (PES) indicated that the closed‐shell 5s² orbitals of Sn²⁺ ions heavily contribute to the hole conduction path in SnO. Top gate type TFTs (W/L = 300/50 µm) employing 20 nm thick SnO channels exhibited field‐effect mobilities µ_sat = 0.7 cm² V⁻¹ s⁻¹ and µ_lin = 1.3 cm² V⁻¹ s⁻¹, which are larger by two orders of magnitude than those reported for p‐channel oxide TFTs to date. On/off current ratios were ∼10² and subthreshold voltage swings (S) ∼7 V/decade. The parameters required for TFT simulations were estimated by ultraviolet PES and first‐principles calculations. The TFT simulations indicated that subgap hole trap density in the SnO channel is >10¹⁹ cm⁻³, which limits the TFT mobilities and the S values.

Based upon ab initio electronic structure calculations by the Korringa–Kohn–Rostoker coherent‐potential approximation (KKR‐CPA) method within the local‐density approximation (LDA), we propose a unified physical picture of magnetism and an accurate calculation method of Curie temperature (T _C) in dilute magnetic semiconductors (DMSs) in II–VI and III–V compound semiconductors. We also propose the unified physical picture of magnetism in the DMS, where ferromagnetic Zener's double‐exchange mechanism (or Zener's p–d exchange mechanism) caused by the partially occupied impurity band and anti‐ferromagnetic super‐exchange mechanism (or ferromagnetic super‐exchange mechanism) is competing to determine the magnetic states in the DMS. We propose that the three‐dimensional 3D Dairiseki‐phase and one‐dimensional 1D Konbu‐phase caused by spinodal nano‐decomposition are responsible for high‐T _C phase in the inhomogeneous system. We propose the new methodology to go beyond LDA to describe the highly correlated electron system by taking into account the self‐interaction correction (SIC) to the LDA. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The development and properties of titanium dioxide (TiO₂)‐based transparent conducting oxides (TCO), which exhibit properties comparable to those of In_2–xSn_xO₃ (ITO), are reviewed in this article. An epitaxial thin film of anatase Ti_0.94Nb_0.06O₂ exhibited a resistivity (ρ) of 2.3 × 10⁻⁴ Ω cm and internal transmittance of ∼95% in the visible light region. Furthermore, we prepared polycrystalline films with ρ of 6.4 × 10⁻⁴ Ω cm at room temperature on glass substrates by using sputtering. We focus on characteristics unique to TiO₂‐based TCO, such as a high refractive index, high transmittance in infrared, and high stability in reducing atmospheres. Possible applications of TiO₂‐based TCOs, as well as the mechanism of the transparent conducting properties found in this d‐electron‐based TCO, are discussed in this review.

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Photograph showing TiO₂‐based TCO on a transparent plastic film. Note that the film appears greenish due to interference in the film originating from its high refractive index. This high refractive index is one of the unique characteristics of TiO₂‐based TCO.

Thin films of Cu₂ZnSnS₄ (CZTS), a potential candidate for absorber layer in thin film heterojunction solar cell, have been deposited by spray pyrolysis technique onto soda‐lime glass substrates held at a substrate temperature (T_s) of 643 K. The effect of copper salt and thiourea concentrations on the formation of Cu₂ZnSnS₄ thin films is investigated. CZTS films formed under optimized conditions are found to be polycrystalline in nature with kesterite structure. The lattice parameters are found to be a = 0.543 nm and c = 1.086 nm. The optical band gap of these films is found to be 1.43 eV. It is found to increase with decrease in copper salt concentration in the solution.

The aim of this paper is to summarise recent progress in the growth of small grain‐sized Chemical Vapor Deposition (CVD) diamond often called nanocrystalline diamond, i.e., diamond with grains typically smaller than 500 nm. Nanocrystalline (NCD) and Ultrananocrystalline diamond (UNCD) films are new materials offering interesting applications to nanobioelectronics and electrochemistry. However NCD and UNCD thin films comprise of entirely different structures which is highlighted here in this paper. We discuss in detail the main differences in Raman spectra, optical properties and electrical transport properties. Finally we present a simple model of the conductivity mechanism in nitrogenated UNCD (N‐UNCD) and boron doped NCD (B‐NCD) films, and show the possibility of achieving the superconductive transition in B‐NCD films. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)