This review summarizes Raman scattering data for different stable and metastable phases of vanadium oxides. We analyze literature data on crystal structures existing in the binary vanadium‐oxygen system. If available, we combine these data with experimental Raman spectra and relations of vibrational modes with the atomic arrangements and motions in crystals. Further, we employ arc sputtering to produce vanadium oxide films, including α and β‐vanadium, V14O6, VO, V2O3, V3O5, several phases of VO2, V6O13, V3O7, and V2O5, as confirmed by X‐ray diffraction analysis. All the films are studied using Raman spectroscopy: low‐ and high‐temperature V3O5 and VOx (1.67 < x < 2) are investigated for the first time. We demonstrate that a significant change in the V3O5 spectrum takes place along the phase transition occurring at approximately 140 °C. Moreover, we describe differences between the spectra of VO2 polymorphs produced without doping impurities, VO2 (M1), VO2 (M2), and VO2 (T). Finally, we analyze conflicting data on V7O16 and V3O7 and provide an explanation of the observed spectra. Overall, 21 spectra are identified for 53 known phases. Our work is aimed at laying the groundwork for easy identification of vanadium oxide phases in thin films, using Raman spectroscopy.

Systematic and in-depth studies of the structure, composition, and efficiency of hydrogen evolution reactions (HERs) in MoSx films, obtained by means of on- and off-axis pulsed laser deposition (PLD) from a MoS2 target, have been performed. The use of on-axis PLD (a standard configuration of PLD) in a buffer of Ar gas, with an optimal pressure, has allowed for the formation of porous hybrid films that consist of Mo particles which support a thin MoSx~2+δ (δ of ~0.7) film. The HER performance of MoSx~2+δ/Mo films increases with increased loading and reaches the highest value at a loading of ~240 μg/cm2. For off-axis PLD, the substrate was located along the axis of expansion of the laser plume and the film was formed via the deposition of the atomic component of the plume, which was scattered in Ar molecules. This made it possible to obtain homogeneous MoSx~3+δ (δ~0.8–1.1) films. The HER performances of these films reached saturation at a loading value of ~163 μg/cm2. The MoSx~3+δ films possessed higher catalytic activities in terms of the turnover frequency of their HERs. However, to achieve the current density of 10 mA/cm2, the lowest over voltages were −162 mV and −150 mV for the films obtained by off- and on-axis PLD, respectively. Measurements of electrochemical characteristics indicated that the differences in the achievable HER performances of these films could be caused by their unique morphological properties.

No abstract

X-ray refractive lenses are proposed as a Fourier transformer for highresolution X-ray crystal diffraction. By employing refractive lenses the wave transmitted through the object converts into a spatial intensity distribution at its back focal plane according to the Fourier-transform relations. A theoretical consideration of the Fourier-transform technique is presented. Two types of samples were studied in Bragg reflection geometry: a grating made of strips of a thin SiO 2 film on an Si substrate and a grating made by profiling an Si crystal. Fourier patterns recorded at different angles along the rocking curves of the Si 111 Bragg reflection were analysed.

We report on the synthesis of titanium suboxide films using a magnetron sputtering setup. The structure of the produced films is characterized using Raman spectroscopy and X-ray diffraction and electrical properties are measured by four-probe method. We demonstrate that depending on the oxidation rate of the growing films it is possible to produce polycrystalline α-TiO, corundum and orthorhombic Ti 2 O 3 or almost amorphous TiO 2 . We focus on the characterization of the two phases of Ti 2 O 3 and show that their structure and electrical properties significantly differ from earlier results obtained for bulk crystals or epitaxial films. Our corundum-type Ti 2 O 3 films have high electrical conductivity (compared to the bulk) and no metal-insulator phase transition: the material is locked in the metallic state. The conductivity of our orthorhombic Ti 2 O 3 is lower compared to epitaxial films; this phase does not demonstrate any phase transitions as well. IntroductionThe first report on titanium sesquioxide (titanium III oxide, or Ti 2 O 3 ) crystal structure was published more than 90 years ago [1]. This material normally crystallizes into corundum-type space group R c with lattice parameters of a = 5.157 Å and c = 13.61 Å. Ti 2 O 3 attracted some interest due to a broad semiconductor to metal phase transition in the temperature range of 150-300 °C [2, 3]. This transition is accompanied by a rapid change of physical properties such as electrical resistivity [4], specific heat [5], elastic constants [6], and magnetic susceptibility [7]. Very recently it was shown that nanoparticle-based Ti 2 O 3 films could be used as an efficient photothermal material promising for seawater desalination and purification [8]. Under high pressures and high temperatures (19 GPa and 1850 K) corundum Ti 2 O 3 phase transforms into golden semiconducting Th 2 S 3 -type structure, which is fully quenchable to ambient conditions (Pnma orthorhombic cell, a = 7.82 Å, b = 2.85 Å, c = 8.12 Å at ambient conditions) [9, 10].Recently, it was shown that Ti 2 O 3 could crystallize into another space group, Immm, with orthorhombic cell parameters of a = 9.39 Å, b = 4.42 Å and c = 2.81 Å. The material was obtained as an epitaxial thin film on (0001) sapphire substrate using pulsed laser deposition and Ti 2 O 3 target at substrate temperatures above 700 °C [11]. Such films are ferromagnetic n-type semiconductors with a very high electron concentration and they also demonstrate a semiconductor to metal transition at about 370 K. The synthesis of the same material by cathodic arc sputtering was reported in our previous article, but that time the phase was not properly identified and characterized [12].In most studies, titanium suboxides are produced by different chemical methods, including carbothermic [13], metallothermic [14] or hydrogen [15] reduction of TiO 2 or by oxidizing different titanium-containing precursors, such as TiCl 3 [16], TiH 2 [17], titanium-tetraisopropoxide [18], and others. These methods usually lead to the formation of the bulk o...