Cage effect of film mesoscopic structure on activation of TiZrHfV non-evaporable getter

The TiZrHfV non-evaporable getter (NEG) film is considered a highly promising getter material in the high or ultra-high vacuum required environments such as particle accelerators, MEMS devices, and tokamak fusion test reactors. However, the passivation layer due to air exposure needs to be removed by thermal vacuum activation prior to use. The objective of this research is to elucidate the activation mechanism of TiZrHfV NEG films. To achieve this, the film morphologies and structural characteristics were investigated using scanning electron microscopy (SEM) and grazing incidence X-ray diffraction (GIXRD). The Monte Carlo method was used to study the characteristics of amorphous structures. The compositional variations at the film surface were detected by in-situ X-ray photoelectron spectroscopy (XPS). After analysis, the cage effect was discovered and the key factor in influencing the activation of the NEG films was identified. Moreover, a criterion for studying the activation behavior of NEG films was proposed. These findings not only improve our understanding on the activation of TiZrHfV NEG films, but also provide valuable insights for scientists to design high-performance novel NEG films. •The migration behavior of foreign atoms is related to film mesoscopic structures.•Activation of different film atomic clusters may not occur simultaneously.•Whether cage effect works is a criterion to determine the film activation status.