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Highly-doped ZnO:Al,N films were grown under oxygen-rich conditions on Si substrates by magnetron sputtering using a layer-by-layer growth technique. An investigation of the highly-doped ZnO:Al,N films is attractive for obtaining p -type conductivity in ZnO films as well as for an improvement of performance of ZnO-based ultraviolet (UV) detectors. X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and Secondary ion mass spectrometry (SIMS) were used for the samples characterization. An effect of high Al and N doping on structure and electronic properties of ZnO films was studied and discussed. [ABSTRACT FROM AUTHOR]

Abstract: Total and partial densities of states of the constituent atoms of iron tungstate, FeWO4, and cobalt tungstate, CoWO4, have been calculated using the first-principles self-consistent full potential linearized augmented plane wave (FP-LAPW) method. The results obtained reveal that the O 2p-like states are the dominant contributors into the valence band of the tungstates under consideration, whilst the bottom of the conduction band of FeWO4 and CoWO4 is dominated by contributions of the empty Fe 3d- and Co 3d-like states, respectively. The FP-LAPW data indicate that the O 2p-like states contribute mainly into the top of the valence band, with also significant contributions throughout the whole valence-band region, of FeWO4 and CoWO4 compounds. Other significant contributors into the valence-band region are the Fe 3d- and W 5d-like states in FeWO4 and the Co 3d- and W 5d-like states in CoWO4. All the above d-like states contribute throughout the whole valence-band region of the tungstates under consideration, however maximum contributions of the W 5d-like states occur in the lower, whilst the Fe (Co) 3d-like states in the upper portions of the valence band, respectively. To verify the above FP-LAPW data, the X-ray emission bands representing the energy distributions of mainly the valence O p-, Fe (Co) d-, Fe (Co) p- and W d-like states were measured and compared on a common energy scale with the X-ray photoelectron valence-band spectrum of the corresponding tungstate. The experimental data were found to be in good agreement with the theoretical FP-LAPW results for the electronic structure of FeWO4 and CoWO4 compounds. [Copyright &y& Elsevier]

Abstract: Iron tungstate (FeWO4) and cobalt tungstate (CoWO4) nanostructures were prepared by the hydrothermal method using sodium tungstate (Na2WO4·2H2O), ferrous ammonium sulfate [(NH4)2Fe(SO4)2·6H2O] and cobalt chloride (CoCl2·6H2O) solutions as precursors. The crystal structure and morphology of the as-prepared tungstates were characterized by X-ray diffraction analysis and transmission electron microscopy. The above characterizations render that the products obtained belong to the monoclinic crystal system and P2/a space group, with average sizes of nanoparticles of about 150nm and 70nm in the case of FeWO4 and CoWO4, respectively. Electronic properties of the FeWO4 and CoWO4 tungstates were studied using several X-ray spectroscopy methods, mainly X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS). The XPS valence-band and core-level spectra, the XAS W LIII edges (unoccupied W d-like states) as well as the XES bands reflecting the energy distribution of the valence W d- and O p-like states were recorded. The present XPS and XAS results reveal that the as-prepared FeWO4 and CoWO4 tungstates are in a composition close to a stoichiometric one. The XES results render that the W 5d- and O 2p-like states contribute throughout the whole valence-band region of the FeWO4 and CoWO4 tungstates, 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. [Copyright &y& Elsevier]

Abstract: Electronic properties of Ti4Fe2O oxide, a very promising hydrogen-storage material, were studied both from theoretical and experimental points of view employing the first-principles band-structure augmented plane wave+local orbitals (APW+LO) method with the WIEN2k code as well as X-ray photoelectron spectroscopy (XPS) and soft X-ray emission spectroscopy (SXES). Total and partial densities of states of the constituent atoms of Ti4Fe2O have been derived from the APW+LO calculations. The XPS valence-band spectra as well as the SXES Ti Lα, Fe Lα and O Kα bands have been measured for a series of Ti4Fe2O x oxides (x =1.0, 0.5, and 0.25). The present APW+LO calculations reveal that, the O 2p-like states are the dominant contributors into the bottom of the valence band, whilst the top of the valence band and the bottom of the conduction band of Ti4Fe2O are dominated by contributions of the Fe 3d- and Ti 3d-like states. The APW+LO results are confirmed experimentally by a comparison on a common energy scale of the XPS valence-band spectra and the SXES Ti Lα, Fe Lα and O Kα bands of the Ti4Fe2O x oxides. The XPS Ti 2p, Fe 2p and O 1s core-level binding energies have been measured for the compounds under consideration. [Copyright &y& Elsevier]

Abstract: First-principles self-consistent band-structure calculations of potassium titanyl arsenate, KTiOAsO4 (KTA), have been made using the full potential linearized augmented plane wave (FP-LAPW) method. Total and partial densities of states of the constituent atoms of KTA have been derived. The results obtained show that the valence band of KTA is dominated by contributions of the O 2p-like states, while the Ti 3d-like states are the main contributors into the conduction band of the compound. Additionally, the FP-LAPW calculations have revealed that potassium atoms are highly ionized in KTA. In the present work, the X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) methods were also employed to investigate experimentally the electronic structure of potassium titanyl arsenate. For the mentioned compound, the XES K Ll, Ti Lα, As Kβ2 and O Kα bands reflecting the valence K s-, Ti s,d-, As p- and O p-like states, respectively, were derived and compared on a common energy scale with the XPS valence-band spectrum. A rather good agreement of the experimental XES and XPS results and the theoretical FP-LAPW data for electronic properties of KTA has been obtained in the present paper. [Copyright &y& Elsevier]

Abstract: To investigate the influence of substitution of carbon atoms for nitrogen atoms in the cubic TaC x N1− x carbonitrides, total and partial densities of states were calculated for TaC, TaC0.5N0.5 and TaN compounds (NaCl structure) using the self-consistent cluster (with the FEFF8 code) and ab initio band-structure augmented plane wave+local orbitals (APW+LO) methods. In the present work a rather good agreement of the theoretical FEFF8 and APW+LO data for electronic properties of the TaC x N1− x system under consideration was obtained. The results indicate that a strong hybridization of the Ta 5d- and C(N) 2p-like states is characteristic for the valence band of the TaC x N1− x carbonitrides. When going from TaC to TaN through the TaC0.5N0.5 carbonitride, the main maxima of curves representing total and partial Ta 5d densities of states shift in the direction opposite to the position of the Fermi level. In the above sequence of compounds, an increase of occupation of the near-Fermi sub-band formed by contributions of Ta 5d(t 2g) states has been detected. The theoretical FEFF8 and APW+LO results for the electronic structure of the TaC x N1− x carbonitrides were found to be in excellent agreement with the experimental data derived in the present work employing X-ray photoelectron, emission and absorption spectroscopy methods for cubic TaC0.98, TaC0.52N0.49 and TaN0.97 compounds. [Copyright &y& Elsevier]

Abstract: X-ray photoelectron spectroscopy (XPS), X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) methods were employed in the present work to investigate the electronic structure of almost stoichiometric cubic (NaCl structure) Hf x Ta1–x C y carbides. The XPS valence-band and core-level spectra, the XES bands reflecting energy distributions of mainly the Ta 5d- and C 2p-like states as well as the XAS Ta LIII edges (unoccupied Ta d-like states) were derived and compared on a common energy scale for cubic HfC0.95, Hf0.5Ta0.5C0.94 and TaC0.98 compounds. To investigate the influence of substitution of tantalum atoms for hafnium atoms in the Hf x Ta1–x C y carbides, cluster self-consistent calculations of total and partial densities of states were carried out with the FEFF8 code for HfC, Hf0.5Ta0.5C and TaC compounds possessing the NaCl-type structure. In the present work a rather good agreement of the experimental and theoretical results for the electronic structure of the Hf x Ta1−x C y system under study was obtained. The results indicate that a strong hybridization of the Hf(Ta) 5d- and C 2p-like states is characteristic for the Hf x Ta1−x C y carbides. It has been established that, substitution of hafnium atoms by tantalum atoms in the Hf x Ta1−x C y system reveals increasing the half-width of the XES C Kα band. When going from HfC0.95 to TaC0.98 through the carbide of intermediate composition, the main maximum of the XPS valence-band spectrum shifts in the direction opposite to the position of the Fermi level. In the above sequence of compounds the asymmetry index of the C Kα bands decreases significantly. [Copyright &y& Elsevier]

Abstract: X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) methods were employed in the present paper to investigate the electronic structure of face-centred cubic (fcc) molybdenum dioxide, fcc-MoO2. For the mentioned compound, the XES O Kα and Mo Lβ2,15 bands reflecting the valence O p- and Mo s,d-like states, respectively, were derived and compared on a common energy scale with the XPS valence-band spectrum. For comparison, the similar experimental studies of the electronic structure were made for a usual orthorhombic form of molybdenum trioxide, MoO3. Band-structure calculations of fcc-MoO2 were made using the full potential linearized augmented plane wave (FP-LAPW) method. A rather good agreement of the experimental XES and XPS results and the theoretical FP-LAPW data for the electronic properties of fcc-MoO2 has been achieved in the present paper. A new near-Fermi sub-band was detected on both the XES Mo Lβ2,15 band and the XPS valence-band spectrum when going from orthorhombic MoO3 to fcc-MoO2. The FP-LAPW calculation reveals that the main contributors into the aforementioned sub-band of fcc-MoO2 are the Mo 4d(eg) states. Further, the FP-LAPW data indicate that the O 2p and Mo 4d(t2g) states contribute into both the central part and the bottom of the valence band of fcc-MoO2, while the Mo 4d(eg) states contribute almost exclusively into the bottom of the valence band of the oxide. A significant portion of density of states (mainly Mo 4d(eg) states) detected by the FP-LAPW calculation at the Fermi energy of fcc-MoO2 indicates that the oxide is rather unstable. [Copyright &y& Elsevier]

The synthesis, structural characterization, and magnetic properties of La 3 Mn 2 NbO 9 double perovskite are reported. The crystal structure has been refined by X-ray and neutron powder diffraction data in the monoclinic space group P2 1 /n. The Mn2+, Mn3+ and Nb5+ cations are distributed at the 2d and 2c Wyckoff sites, with a high cation order degree in the latter, mainly occupied by Mn2+/Mn3+. The Mn3+ presence was established from X-ray Emission Spectroscopy and X-ray Photoelectron Spectroscopy. Rietveld refinements of powder neutron diffraction data show that at room temperature the cell parameters are a= 5.6063(3) Å, b= 5.8155(3) Å, c= 7.9877(2) Å y β= 89.89(1)°. Magnetization measurements indicate the presence of ferromagnetic and antiferromagnetic interactions with T C ∼19 K and T N ∼11 K, respectively, with a magnetic cell of symmetry Γ 1 (A g). The analysis of the neutron data suggests a canted ferrimagnetic spin structure where an antiferromagnetic unit-cell in a and c axis, and ferromagnetic in b axis with a propagation vector k = (0 ½ 0) was used. The effective magnetic moment obtained experimentally is μ eff = 5.50 μ B /mol Mn2+/3+, slightly lower than the theoretical one for spin only (5.83 μ B). • Synthesis of new double perovskite La 3 Mn 2 NbO 9. • Canted ferrimagnetism due to the high degree of structural distortion. • Effective existence of Mn2+/Mn3+ mixture. • Multiple possible magnetic interactions and huge distortion of the octahedral network allow AFM and FM couplings. [ABSTRACT FROM AUTHOR]

In this communication, indium oxide (In 2 O 3) and Zn-doped In 2 O 3 nanoparticles with different zinc percentage (0–5%) have been prepared by a facile chemical process. A variety of analytical tools such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, UV–Visible, photoluminescence spectroscopy, photocatalytic measurements and impedance spectroscopy were employed to assess the characteristics of prepared nanoparticles (NPs). From XRD analysis it is observed that all samples exhibit pure cubic phase with highly crystalline nature. XPS spectra revealed the composition and chemical state of Zn-doped In 2 O 3 NPs. The estimated optical band gap was found to decrease with increase of Zn concentration. Magnetic hysteresis exhibited that pure and Zn-doped In 2 O 3 NPs possess ferromagnetic behavior at room temperature. Dielectric constant (ε ') as well as dielectric loss (ε ") decreases exponentially in lower frequency range, but remains almost constant in higher frequency range. Moreover, Zn(5%)-doped In 2 O 3 nanoparticles showed much higher photocatalytic activity as compared with pure In 2 O 3 nanoparticles towards degradation of hazardous methylene blue dye. The results of present study demonstrated that synthesized nanoparticles may be employed efficiently as environmentally convenient photocatalyst for industrial effluent treatment. • Pure and zinc (Zn) loaded indium oxide (In 2 O 3) nanoparticles were prepared by a facile chemical process. • Structure and morphology characterization was performed by XRD and SEM. • The dielectric constant and dielectric loss have been investigated as a function of frequency 120 Hz to 0.1 MHz.. • In 2 O 3 –Zn nanoparticles exhibit superior photocatalytic activity than that of pure In 2 O 3 NPs. • The photocatalytic mechanism was proposed. [ABSTRACT FROM AUTHOR]

The knotted GaN nanowires with huge surface-to-volume ratio and special nanoknots structure have broad application prospects for hydrogen gas sensors, nanoscale piezotronic memristor and optoelectronics. The N-polar GaN nanowires comparing with Ga-polar nanostructures, have higher crystallinity, excellent optoelectronic properties and more sensitive sensing properties, etc. The synthesis of GaN nanowires with the simultaneous integration of the knotted and N-polar have both scientific significance and practical application prospects. Herein, we demonstrate a strategy for constructing high-quality N-polar knotted GaN nanowires on the c -plane sapphire substrate coated with Au layer via a convenient chemical vapor transport approach. The Au-assisted vapor transport initializes the GaN nucleation. The N-polar is acquired by nitridating the surface of substrate through NH 3 , and the knotted nanostructures are then obtained by controlling the reaction of Ga with N to modulate the growth pattern, and thus vapor-solid growth promotes the formation of the knotted nanowires with multiple single GaN pyramids. The morphology, structure, composition and optical properties of the as-synthesized nanowires were investigated through field-emission scanning electron microscopy, field-emission transmission electron microscopy, X-ray diffraction, energy dispersive spectroscopy mapping, X-ray photoelectron spectroscopy, Raman spectrum and photoluminescence spectroscopy. The characterization results confirm that the knotted GaN nanowires have high quality and grow along the polar [000 1 ‾ ] direction, and the widths of knotted hexagonal cross-sections are 80–320 nm and their average length is approximately 6 μm. The N-polar knotted GaN nanowires with unique nanostructures grown on the substrate can be promising candidates for high-performance nanoscale optoelectronic and photocatalytic devices and hydrogen gas sensors. • N-polar GaN nanowires with knotted nanostructures were synthesized via a convenient CVD method. • The top surface of GaN nanowires is N-polar plane acquired by nitridating the surface of substrate through NH 3. • The side surfaces of GaN nanowires are composed of semi-polar planes. • The growth pattern can be modulated by the concentration of Ga to obtain knotted GaN nanowires. [ABSTRACT FROM AUTHOR]