Formation Mechanism of Passivation Layer under Air Exposure on TiZrV Non-Evaporable Getter Film

Abstract

Non-evaporable getter (NEG) films require thermal vacuum activation prior to their use in high vacuum environments. The degree of activation difficulty is influenced by the properties of the passivation layer, but there is limited information about its composition. The purpose of this study is to investigate the formation mechanism and clarify this issue. The film microstructure was investigated by scanning electron microscopy (SEM) and grazing incidence X-ray diffraction (GIXRD). The quantum chemical approach and a single-metal-atom catalytic model were used to calculate the energy barrier for the reactions between the metal atom and the gas molecule, as well as between different hydrocarbon groups. These results facilitated the deconvolution of the X-ray photoelectron spectroscopy (XPS) data and the variation analysis of the energy dispersive spectroscopy (EDS) results. It can be concluded that the presence or absence of hydrogen-proton catalysis can significantly affect the dissociation pathways of carbon dioxide, leading to the formation of different reaction products. In addition, the long-term aluminum foil wrapping and storage can significantly affect the composition of the film passivation layer. This study provides valuable insights not only into the passivation layer formation mechanism, but also into the film gettering mechanism.