Anion Doping of Tungsten Oxide with Nitrogen: Reactive Magnetron Synthesis, Crystal Structure, Valence Composition, and Optical Properties

Anion doping of tungsten trioxide by nitrogen is used to obtain electrochrome cathode materials, the spectral transmittance of which can be controlled by the doping level. A series of samples was synthesized by reactive magnetron sputtering of a metal tungsten target in a mixture of argon, nitrogen, and oxygen gases, the flow rate of the latter was varied at a constant pressure of the gas mixture. Warm-colored tungsten oxynitride films were prepared at higher doping levels with their morphology and elemental composition characterized using scanning electron microscopy, crystal structure described using X-ray diffraction and the valence state of constituents revealed with X-ray photoelectron spectroscopy techniques. Optical properties were measured by making use of transmission spectrophotometry and spectroscopic ellipsometry. These extensive experimental studies revealed an increase in absorption towards shorter wavelengths below the wavelength of 0.5 µm with an increase in the doping level. At the same time, it was found that with an increase in the doping level, partial reduction of the tungsten occurs, and the fraction of non-stoichiometric oxygen steadily increases to half of the total oxygen content. It is a common belief that the imperfection of the doped material facilitates the intercalation of the material by electrolyte ions

Ion-Beam Synthesis of Structure-Oriented Iron Nanoparticles in Single-Crystalline Rutile TiO₂

Magnetic nanoparticles embedded into semiconductors have current perspectives for use in semiconducting spintronics. In this work, 40 keV Fe+ ions were implanted in high fluences of (0.5 ÷ 1.5) × 1017 ion/cm2 into an oxide semiconductor and single-crystalline TiO2 plates of rutile structure with (100) or (001) face orientations. Microstructure, elemental-phase composition, and magnetic properties of the Fe-ion-implanted TiO2 were studied by scanning and transmission electron microscopies (SEM and TEM), X-ray photoelectron (XPS) and Rutherford backscattering (RBS) spectroscopies, as well as vibrating-sample magnetometry (VSM). The high-fluence ion implantation results in the formation of magnetic nanoparticles of metallic iron beneath the irradiated surface of rutile. The induced ferromagnetism and observed two- or four-fold magnetic anisotropy are associated with the endotaxial growth of Fe nanoparticles oriented along the crystallographic axes of TiO2

Sur les possibilités de reconstitution paléo-environnementale offertes par les andosols des hautes terres tropicales : exemple des Nilgiri (Inde du Sud)

Un exemple, pris en Inde du Sud, montre les potentialités offertes par l'étude d'andosols non allophaniques d'altitude pour reconstituer l'histoire paléoenvironnementale locale. Dans ce type de sol, la matière organique est stabilisée sous forme de complexes organométalliques qui ne migrent que très lentement. Comparé au signal général enregistré par les tourbières, le signal retenu par la matière organique paraît beaucoup plus ponctuel ; ceci permet des études paléoenvironnementales plus précises. Cette application vient à un moment où des reconstitutions paléoclimatiques précises sont nécessaires pour bâtir des modèles climatiques fiables. (Résumé d'auteur