In this paper, the electronic structures of NbO2 and Nb2O5 are theoretically and experimentally analyzed. The oxides in the samples are mainly consisted of NbO2 and NbO, whereas the outmost layer of the samples is NbO2. After exposure to air, the outermost layer on all niobium samples is Nb2O5. The photoelectrons from the first 2–4 Å contribute to the spectra, so the valence band structure of NbO2 and Nb2O5 can be confirmed from ultraviolet photoelectron spectroscopy (UPS). By comparing the UPS with density of state results, the electronic structure of NbO2 and Nb2O5 can be distinguished from each other, and then the electronic structure was deconvoluted into several electronic states. The agreement between experimental result and theory is, in the best case, satisfactory. Copyright © 2013 John Wiley & Sons, Ltd.

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N-doped diamond-like carbon (DLC) films were deposited on Si substrates by pulsed laser deposition (PLD) at varying N 2 pressure. The films were characterized by Raman spectroscopy and X-ray diffraction (XRD). Spectra show that the sp 2 hybridized carbon content increases with increasing N 2 pressure and that the films have a mainly amorphous structure. The residual stress of the films is reduced from 31.8 to −2.2 GPa by N-doping at appropriate N 2 pressure. Diamond-like carbon (DLC) films have many superior properties, including mechanical hardness, dielectric strength, chemical inertness, low coefficient of friction, and optical transparency in the infrared ranges, making them promising for a wide range of applications [1,2]. They can be synthesized by a variety of methods, including pulsed laser deposition (PLD) [2,3] and, under some conditions, filtered cathodic vacuum arc (FCVA) deposition [4]. DLC properties approach those of crystalline diamond. However, the films have very high intrinsic stress [5,6] and consequently tend to exhibit low adhesion with increased thickness [5,6], thus severely limiting their practical applications.Alloying amorphous carbon (a-C) films with transition metals such as Ni, Co, Ti, Mo, and W is a common strategy for reducing residual stress in DLC films [7]. The effects of dopants such as B, P, and N on the microstructure, electrical structure, and mechanical and optical properties of a-C films have been studied. However, there has been no extensive study on the effect of nitrogen concentration on the properties of N-doped DLC films.In this work, we prepared N-doped DLC films by PLD at varying N 2 pressure. We then investigated the structure and residual stress of the films by Raman spectroscopy and X-ray diffraction (XRD).N-doped diamond-like carbon films were deposited on Si wafers by PLD at room temperature. The distance between target and substrate was 4 cm. The excimer laser energy density was 7.5 J/cm 2 . Nitrogen pressure was in the range 8-20 × 10 −3 Pa.The crystal structures and residual stresses of the films were determined by X-ray diffraction (X Pert PRO) us-