Lowering the activation temperature of Ti-Zr-V non-evaporable getter films by removing surface carbon contamination: An in situ XPS study

Distributed pumping on the inner walls of ultrahigh vacuum (UHV) chambers using thin films of non-evaporable (NEG) getters has shown its large potentialities in particle accelerators in terms of pumping speed, ultimate pressures, outgassing/degassing rates and low secondary electron yields. The successful ternary combination of titanium, vanadium and zirconium provides large pumping speeds for 1–2 μm thick films with activation temperatures of 180 °C. However, for several UHV systems this temperature is still too high for the delicate instrumentation they host such as optics in beamlines of synchrotron radiation and free-electron lasers facilities. Thus, the quest for lower activation temperatures continues to be an important objective in the particle accelerators and storage rings community. In this study, we show that the removal of surface carbon contamination in Ti-Zr-V NEG films can decrease the activation temperature down to 150 °C, thus approaching the bakeout temperatures that the delicate instrumentation can withstand. Carbon removal is achieved by means of in situ low-pressure inductively-coupled downstream RF plasma and the evidence of surface cleaning and activation is assessed by monitoring the reduction of surfaces oxides with in situ X-ray photoemission spectroscopy (XPS). We present experimental conditions under which the films become virtually fully activated and test the effect of the plasma on silicon wafers emulating surfaces used in X-ray optics. • Activation of Ti-Zr-V non-evaporable getter films characterized by in-situ XPS. • Full activation achieved at 150C for 20 h after in situ carbon removal. • Carbon contamination removed by low-pressure inductively-coupled RF plasma. • Plasma treatment using an argon/oxygen gas mixture (80 %:20 %) at 5 × 10 −3 mbar and 60 W. • Silicon wafers exposed to the same plasma conditions as test samples for potential use in synchrotron radiation facilities.