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Abstract: Calcium barium niobate (Ca0.28Ba0.72Nb2O6, CBN-28) crystallizes with an unfilled tungsten bronze (TB) type structure in the tetragonal system. X-ray photoelectron spectroscopy (XPS) has been performed to explore the effect of Nd-doping on the local electronic environment in the CBN-28 crystal. The content of oxygen vacancies is increased after Nd-doping. The Raman scattering spectrum has been investigated using the back scattering configuration on a CBN-28 crystal and on a crystal with Nd-doping. Comparison of the Raman data obtained for the undoped and Nd-doped CBN-28 crystals reveals slight differences in the shape and position of the Raman peaks. The difference is not readily apparent due to the low Nd3+ content and the intrinsic disorder of the tetragonal tungsten bronze structure. [Copyright &y& Elsevier]

Abstract: X-ray photoelectron spectroscopy has been used to examine the chemical nature of titanium nitride (TiN) films deposited by reactive unbalanced magnetron sputtering under different substrate biases (ranging from 0 to -500V). Before Ar+ sputtering, three groups of Ti 2p doublet, related to TiN, TiON and TiO2, were observed in the core level spectra of the deposited TiN films. The intensity of peak from TiO2 decreases drastically with the increasing substrate bias, reaching a minimum at a bias voltage of –100V, and then increases greatly. However, the intensity of peak from TiN shows an opposite behavior with its maximum value at –100V. Furthermore, the nonlinear intensity variation of these peaks was accompanied with obvious nonlinear trend of peak shift. Similar tendency was found for the N 1s spectra of these films. After Ar+ sputtering, the Ti 2p and N 1s region of bulk TiN both displayed a nonlinear peak shifting with their highest binding energy at a bias voltage of –50V. The reason for the different optimum bias between the surface and the bulk were considered to be the incorporation and diffusion of oxygen near surface. The appropriate substrate bias was believed to be helpful for the bonding and formation of stoichiometric TiN, hinder the generation of surface oxide and restrict the initiation of impurities and defects in both surface and bulk materials. Our atomic force microscopy study also revealed a nonlinear trend of surface morphology and root-mean-square roughness. As a combined effect from improved surface morphology, significantly restricted surface oxidation and well-bonded stoichiometric TiNx in both native surface and bulk material, the best hardness was measured to be about 32GPa at optimum bias of –100V. [Copyright &y& Elsevier]

Abstract: La2NiO4 compounds were prepared by a modified sol–gel auto-combustion method, which is a low-temperature combustion synthesis procedure using microwave-assisted sol–gel as precursors. The high-temperature transport properties of the samples were investigated. The band structure, total density of states (DOS), and partial density of states (PDOS) of low-temperature orthorhombic (Bmab) phase and high-temperature tetragonal (I4/mmm) phase for La2NiO4 were calculated in order to study the transport properties of the as-obtained samples. [Copyright &y& Elsevier]

Abstract: The transport properties of N,N′-diphenyl-N,N′-bis(1-naphthyl)-1,1′-biphenhyl-4,4′-diamine (NPB) have been investigated by using impedance spectroscopy (IS) and J–V measurements based on a single-layer structure of ITO/NPB/Al. The J–V characteristic of the device obeys Ohmic law below 0.6V, and is in the space-charge limited current (SCLC) regime above 0.6V. The density of the thermally generated charge carrier is determined to be about 3.1×1016 cm−3. Impedance spectroscopy measurements showed that the device can be simulated by an equivalent parallel RC network with a contact resistance R S in series, in which the bulk capacitance C of NPB remains unchanged while the resistance R decreases along with bias voltage. The variation of the whole conductance and capacitance of the device with frequency and bias can be understood by the carrier response and the transit time dependence on the bias in the NPB film. [Copyright &y& Elsevier]

The electronic structure of a cyclooctatetraene derivative COT-H deposited on Ru(1 0 1¯ 0) has been studied using ultra-violet photoemission spectroscopy (UPS). The highest occupied molecular orbital (HOMO) of COT-H and the other OCT-H derived features are located at about 1.8, 3.8, 5.6, 7.9 and 10.2 eV in binding energy, respectively. With increasing thickness of the COT-H layer, the work function decreases from a value of 4.3 eV on the Ru substrate to a COT-H bulk value of 3.3 eV at a COT-H thickness of 25 A˚. The sharp decrease in work function at the beginning of COT-H deposition is attributed to dipole layer formed at the interface. Using the results from UPS spectra, and taking the optical band gap of 3.3 eV as the HOMO–LUMO band gap of COT-H, the ionization potential of COT-H is determined to be 5.1 eV, and the energy diagram at the COT-H/Ru interface is obtained. [Copyright &y& Elsevier]