A HREELS and NEXAFS characterization of the atomic and molecular oxygen species on a vanadium (110) surface

Separation of valence states in thin films with mixed V2O5 and V7O16 phases

“…It is clear that, at every measurement temperature, the relative intensity of the peak from σ* band compared to peak from π* band is pronounced in the major V7O16 film compared to the film with pure V2O5 phase. These results again prove that, indeed, in the film with a major V7O16 phase, the amount of oxygen is lower, and thus the valence state of the film is lower than in the pure V2O5 film [38][39][40][41][42]. Based on this observation, we also propose that these mixed-valence and mixed phase thin films have more oxygen vacancies in their structure than the pure V2O5 films, in accordance to previous results published [13,17,45,46].…”

“…When the oxidation number, i.e. valence state decreases, the relationship between the electron densities t2g and eg levels is changed, causing a more pronounced relative intensity of the second peak rising from σ* band of the O-K-edge [38][39][40][41][42]. Also in this study, clear differences in the O K-edge peak shapes is seen when a lower valence state phase, i.e.…”

“…Especially, the first peak at around 529.5 eV is much sharper, and has higher intensity in the film with major V2O5 phase in all the measurement temperatures than in the film with the V7O16 presence. This is an indication of higher amount of oxygen in the sample [38][39][40][41][42]. Also, it is noticed in the film with major V2O5 phase, that when the temperature of the sample is increased from RT to 300 ˚C the shape of the peaks at O K-edge are changing, and the differences between the two samples are less pronounced.…”

“…In a pure V2O5 structure, with a valence consisted almost purely from V 5+ ions, the t2g states have a higher electron density than the eg states, and thus the first peak has the dominating maximum, when the O K-edge is probed [38][39][40][41][42]. When the oxidation number, i.e.…”

Synthesis, characterization and surface reactivity of tungsten carbide (WC) PVD films

“…Details concerning the UHV chamber and the beamline have been described previously [25][26][27]. The NEXAFS measurements were recorded by measuring the partial electron yield, which was recorded by a channeltron multiplier located near the sample.…”