XAFS investigations of nitrided NbN–SiO2 sol–gel derived films

Local Fine Structural Insight into Mechanism of Electrochemical Passivation of Titanium

“…Titanium oxidation valences are responsible for the absorption edge position together. ,, Moreover, the bond structures and the coordination condition significantly affect the shape of spectra in the near edge region . Multipeak Gaussian (pseudo Voigt or Lorentzian) fitting by Athena is employed to fit the XANES spectra for quantitative analysis of the oxide of Ti. , The shape variation of the XANES spectra can be related to the applied potentials of the electrochemical activity of passive films . By comparing the peak areas, the ratios of TiO, Ti 2 O 3 , and TiO 2 are quantified, as shown in Figure b.…”

“…XAFS spectra were obtained to correlate the structure and composition of passive film under study with the electronic structure of Ti ions and the local fine structure in their environment. 39 The passive films of titanium potentiostatically polarized for 12 h at seven potentials of interest are detected in terms of electronic structures and compositions by XANES (−20 to 50 eV relative to the absorption edge) and the chemical environments around Ti atom by EXAFS (50−1000 eV after the absorption edge).…”

“…51,64 The shape variation of the XANES spectra can be related to the applied potentials of the electrochemical activity of passive films. 39 By comparing the peak areas, the ratios of TiO, Ti 2 O 3 , and TiO 2 are quantified, as shown in Figure 7b. The ratio of TiO is stably constant at around 30%, because this oxidation is complete as a result of the potential of eq 1 which is −1.871 V SCE and is much lower than the applied potentials.…”

“…To fully understand the passivation and metal protection mechanism, it is necessary to study the structure of passivation on a nanometric scale which cannot be achieved by X-ray diffraction (XRD). X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) are very powerful techniques to provide such sub-nanometric structure information on crystalline and amorphous materials of an electrochemical system. − However, to date, it is not possible to identify the complicated chemical environments in a multielement oxyhydroxide layer formed on metals or alloys by electrochemical treatments, because a direct comparison with known reference hydrooxide and/or oxide bulk compounds is essential, so titanium is a good choice in this research.…”

Effect of disorder on superconductivity of NbN thin films studied using x-ray absorption spectroscopy

“…We note that Nb K-edge splits into two components K1 and K2 (see inset of figure 1(b)). The initial rise K1 is due to the electronic transitions from Nb-1s core level to unoccupied admixed 4d-5p levels while the second absorption rise K2 arises due to transitions from the Nb-1s core level to the Laporte-allowed states of pure 5p symmetry [30,31]. The absorption edge of sample deposited at R N 2 = 16% is shifted towards higher energy by 3 eV as compared to the edge of elemental Nb (see inset of figure 1(b)), which indicates that Nb atom bears positive charge due to the formation of NbN compound.…”