Effect of atomic-scale microstructures on TiZrV non-evaporable getter film activation

Abstract

Non-evaporable getter (NEG) films are widely used in high vacuum technologies and have played a critical role in applications requiring ultrahigh vacuum conditions, such as accelerator vacuum systems. The passivation layers on the film surface due to air exposure generally require thermal vacuum activation. This research aims to elucidate the key factor in the activation of TiZrV NEG films from the perspective of atomic-scale microstructures. The characteristics of film element distributions, morphologies, and crystalline states before and after activation were investigated by energy dispersive spectroscopy, scanning electron microscopy, and grazing incidence x-ray diffraction. In situ x-ray photoelectron spectroscopy was used to detect compositional variations in the film surface layer at different activation temperatures. According to the analysis, from an atomic-scale perspective, the easily activated structures would degrade in activation performance when surrounded by structures that are difficult to activate. During activation, the activated structures tend to act as channels for foreign atoms until the surrounding structures are fully activated. Hydroxyl and carbonyl groups are generally easier to activate than hydrocarbons and surface carbides, but even groups of the same type vary greatly in activation difficulty due to the differences in atomic-scale microstructures on the film surface. These findings provide valuable insight into the activation of NEG films and may be beneficial in the design of novel NEG films with excellent activation performance.