XPS and ESD study of carbon and oxygen chemistry on TiZrV NEG

Abstract

In this work, properties of TiZrV getter films prepared on stainless-steel substrates by magnetron sputtering were investigated. Changes of sample surface during thermal activation and interaction of the activated getter with CO were studied by means of XPS and ESD of neutrals. The XPS measurements reflect the disappearance of the superficial oxide layer coveing air-exposed TiZrV surfaces and the transformation of graphitic carbon to carbides during thermal activation. The dissociative CO adsorption on activated TiZrV getter was observed. Neutral products of electron-stimulated desorption were registered using quadrupole mass spectrometer. The ESD yield of CO and H 2 was measured during thermal activation as well as during CO and H 2 exposure of activated getter. The difference between the ESD yields for CO and H 2 after the exposure indicates possibly different pumping mechanisms for these gases. Hydrogen seems to be incorporated into the bulk while carbon monoxide stays chemisorbed on the getter surface. Although detectable activation proceeds already at temperatures above 160°C, the activation process is reasonably fast (a few hours) at higher temperatures (above 200°C).