Unveiling the secrets of non-evaporable getter films: Activation temperature, activation time, and achievable activation degree

Non-evaporable getter films play an important role in the creating and maintaining of high or ultra-high vacuum environments in advanced scientific disciplines. Prior to application, thermal activation in a vacuum environment is essential. Despite numerous attempts to reduce the film activation temperature, uncertainty remains as to whether extending the activation time at a relatively lower activation temperature will ensure a fully-activated state of the film. To address this issue, the microstructure and activation performance of the film has been investigated. Techniques, such as scanning electron microscopy, grazing incidence X-ray diffraction, energy dispersive spectroscopy, and in-situ X-ray photoelectron spectroscopy were employed. Experimental investigations show that a fully-activated state of the film cannot be achieved at around 150°C, regardless of the activation time. Further analysis shows that, at activation temperatures below about 200°C, the migration trend of oxygen atoms within TiZrV/TiZrHfV films exhibits asynchronous features. This process was accompanied by boundary effects of foreign atom migration channels. In addition, the achievable activation degree of the film shows a step characteristic. These results improve the understanding of the relationship between activation temperature, activation time, and the achievable activation degree of the film.