Near-surface chemistry in $Zr2Fe$ and ZrVFe studied by means of x-ray photoemission spectroscopy: A temperature-dependent study

The near-surface atomic composition and the character of chemical bond in two nonevaporable gettering alloys have been investigated via core level (Zr $3d,$ Fe $2p,$ V $2p,$ O $1s,$ C $1s)$ photoemission. The samples have been measured in UHV after in-air fracturing and various annealing steps (up to 850 °C). For $T>400 °C$ a progressive and sizeable decrease of the near surface C content along with an increase in the Zr concentration is observed in both alloys. An annealing induced Zr enrichment at the surface is found, the metallic atomic concentrations being significantly far from the nominal bulk stoichiometry. The annealing induces a strong evolution in the chemical bonds, the metallic species being completely oxidized in in-air fractured samples while a metallic character progressively emerges at increasing temperatures. Surface metallization proceeds faster in $Zr2Fe$ than in the V-containing getter.