SRPES and XPS Analysis of Activation and Deterioration Processes for Ti-Zr-V NEG Coating

The activation and deterioration mechanisms of the Ti-Zr-V non-evaporable getter (NEG) coating have been investigated. Operando analysis of the surface chemical composition change of the Ti-Zr-V coating was performed by the synchrotron radiation photoelectron spectroscopy (SRPES) during the process of heating the sample to 250°C, corresponding to the activation process of NEG coating. The surface oxidation process was also characterized by the SRPES during the injection of O2 gas into the chamber while keeping the sample at 250°C, corresponding to the deterioration process of NEG coating. The depth profile of the oxidized sample was measured with X-ray photoelectron spectroscopy. The experimental results suggested that the surface Zr gets the oxygen from the oxides of Ti and V at the first stage of the activation process, resulting in the metallic Ti and V on the surface. Then, the oxygen of the Zr-oxide diffuses to the interior of the coating, resulting in the metallic Zr on the surface. It is further suggested that in the deteriorated Ti-Zr-V NEG coating, the Zr, then Ti, is oxidized deep into the coating, resulting in the restriction of oxygen migration from the surface and consequently the lack of surface metallization.