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The bulk band structure of the topological insulator Sb2Te3 is investigated by angle-resolved photoemission spectroscopy. Of particular interest is the dispersion of the uppermost valence band with respect to the topological surface state Dirac point. The valence band maximum has been calculated to be either near the Brillouin zone centre or in a low-symmetry position in the –M¯ azimuthal direction. In order to observe the full energy range of the valence band, the strongly p-doped crystals are counter-doped by surface alkali adsorption. The data show that the absolute valence band maximum is likely to be found at the bulk Γ point and predictions of a low-symmetry position with an energy higher than the surface Dirac point can be ruled out. [ABSTRACT FROM AUTHOR]

We present an experimental study of inelastic scattering processes on the (111) surface of the topological insulator Sb2Te3 using helium atom scattering. In contrast to other binary topological insulators such as Bi2Se3 and Bi2Te3, Sb2Te3 is much less studied and the as-grown Sb2Te3 sample turns out to be p-doped, with the Fermi-level located below the Dirac-point as confirmed by angle-resolved photoemission spectroscopy. We report the surface phonon dispersion along both high symmetry directions in the energy region below 11 meV, where the Rayleigh mode exhibits the strongest intensity. The experimental data is compared with a study based on density functional perturbation theory calculations, providing good agreement except for a set of additional peculiar inelastic events below the Rayleigh mode. In addition, an analysis of angular scans with respect to a number of additional inelastic events is presented, including resonance enhancement, kinematical focusing, focused inelastic resonance and surfing. In the latter case, phonon-assisted adsorption of the incident helium atom gives rise to a bound state where the helium atom rides the created Rayleigh wave. [ABSTRACT FROM AUTHOR]

Polymorphism, morphology, particle size, and defects play key roles in the physical and chemical properties of nanoparticles. In hydrothermal synthesis of metal oxide nanoparticles, it is important to understand the influence of the specific precursor on these characteristics. Here, the formation mechanism of anatase TiO2 nanoparticles by hydrolysis of titanium isopropoxide under hydrothermal conditions is studied by in situ total X-ray scattering and pair distribution function (PDF) analysis. It is shown that the amorphous precursor structure has short-range order up to ~6.5 Å consisting of titanium hydroxide clusters made from TiO6/TiO5 units in an arrangement related to anatase. Insight into the structural disorder of the anatase TiO2 nanocrystals is obtained from both PDF and powder X-ray diffraction (PXRD) analyses. Defects of OH species are present on the surface of the nanocrystals, and their concentration correlates strongly with the particle size. Even though the formation of anatase TiO2 under hydrothermal conditions resembles a solid-state phase transition from amorphous titania, the crystallization and grain growth kinetics of the nanocrystals are different due to the effects of the solvent. [ABSTRACT FROM AUTHOR]

Pressure-induced crystal color change of photo-magnetic materials [Ln(DMF)4(H2O)3(μ-CN)M(CN)5]·H2O, Ln = Y, M = Fe (1), Ln = Y, M = Co (2), Ln = Nd, M = Fe (3) (DMF = N,N-dimethyl formamide) are investigated using variable pressure X-ray Absorption Near-Edge Structure (XANES) spectroscopy and X-ray diffraction. For 1 the effect is caused by ligand-to-metal charge transfer (LMCT) on the iron site. [ABSTRACT FROM AUTHOR]

The bulk band structure of the topological insulator Sb 2 Te 3 is investigated by angle-resolved photoemission spectroscopy. Of particular interest is the dispersion of the uppermost valence band with respect to the topological surface state Dirac point. The valence band maximum has been calculated to be either near the Brillouin zone centre or in a low-symmetry position in the  - M̄ azimuthal direction. In order to observe the full energy range of the valence band, the strongly p-doped crystals are counter-doped by surface alkali adsorption. The data show that the absolute valence band maximum is likely to be found at the bulk Γ point and predictions of a low-symmetry position with an energy higher than the surface Dirac point can be ruled out.

We present an experimental study of inelastic scattering processes on the (111) surface of the topological insulator Sb 2 Te 3 using helium atom scattering. In contrast to other binary topological insulators such as Bi 2 Se 3 and Bi 2 Te 3 , Sb 2 Te 3 is much less studied and the as-grown Sb 2 Te 3 sample turns out to be p-doped, with the Fermi-level located below the Dirac-point as confirmed by angle-resolved photoemission spectroscopy. We report the surface phonon dispersion along both high symmetry directions in the energy region below 11 meV, where the Rayleigh mode exhibits the strongest intensity. The experimental data is compared with a study based on density functional perturbation theory calculations, providing good agreement except for a set of additional peculiar inelastic events below the Rayleigh mode. In addition, an analysis of angular scans with respect to a number of additional inelastic events is presented, including resonance enhancement, kinematical focusing, focused inelastic resonance and surfing. In the latter case, phonon-assisted adsorption of the incident helium atom gives rise to a bound state where the helium atom rides the created Rayleigh wave.