V.L. Bekenev

Electronic Structure of h-WO3 and CuWO4 Nanocrystals, Harvesting Materials for Renewable Energy Systems and Functional Devices

— The electronic structure of hexagonal WO3 and triclinic CuWO4 nanocrystals, prospective materials for renewable energy production and functional devices, has been studied using the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) methods. The present XPS and XES results render that the W 5d-and O 2p-like states contribute throughout the whole valence-band region of the h-WO3 and CuWO4 nanocrystalline materialls, however maximum contributions of the O 2p-like states occur in the upper, whilst the W 5d-like states in the lower portions of the valence band, respectively.

Electronic structure of KTiOAsO4, a novel material for non-linear optical applications

A high-quality KTiOAsO4 (KTA) single crystal has been successfully synthesized employing the high temperature solution growth technique with rotating and pooling. The XPS valence-band spectra have been measured for pristine and the 1.5 keV Ar+ ion-bombarded thin (001)KTA plate cut from the crystal part that was without any optical inhomogeneities or domain boundaries. The present XPS measurements have revealed the existence of two O 2s subbands on the XPS spectrum of the pristine (001)KTA surface. It has been established that 1.5 keV Ar+ ion bombardment of the (001)KTA surface causes the complete elimination of the O 2s sub-band related to oxygen atoms involved in the formation of Ti–O–As bonds in KTA. In addition, the XPS results reveal that such a treatment leads to a significant decrease of the relative intensity of the XPS As5+ 3d core-level spectrum and causes the formation of the additional As0 3d core-level spectrum in the topmost layer of the (001)KTA surface. The experimental data are compared to the results of the first-principles band-structure calculations of KTA.

Electronic Structure of the Face-Centred Cubic MoO1.9 Phase Obtained Due to Reduction of Hydrogen Bronze H1.63MoO3

The electronic structure of face-centred cubic (fcc) MoO x (x = 1.9) oxide derived due to reduction of hydrogen bronze H1.63MoO3 has been studied using the X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) methods. For comparison, the electronic structure of molybdenum trioxide, MoO3, and the H1.63MoO3 bronze was studied as well. The XES O Kα and Mo Lβ2,15 bands of fcc-MoO1.9 and XPS valence-band spectra of the MoO1.9, MoO3 and H1.63MoO3 compounds were derived. Band structure calculations of fcc-MoO2 have been fulfilled using the full-potential linearized augmented plane wave (FP-LAPW) method. The theoretical XES O Kα and Mo Lβ2,15 bands were calculated for fcc-MoO2 employing the above method. A rather good agreement of shapes of experimental and theoretical XES O Kα and Mo Lβ2,15 bands for fcc molybdenum dioxide has been obtained.

On the theory of X-ray K-absorption spectra oftransition elements in intermetallic compounds at theregion of near absorption edge

Abstract Calculated by the self-consistent augmented plane-wave (APW) methodwith accounting for radial factor of probability of transition, and measured experimentally, theK-absorption spectra of Fe in TiFe compound are compared in an energy range of 35 eV abovethe Fermi level. A good agreement between the theory and experiment in the main features ofabsorption curves is found. That proves the appropriateness of the band approach forinterpretation of X-ray absorption K-spectra of 3d-transition elements in intermetallic compounds.