Nonevaporable getter films for ultrahigh vacuum applications

The vacuum behavior of stainless steel vacuum chambers, ex situ sputter coated with a thin film (similar to 1 mu m) of getter material, has been studied to determine if after air exposure the getter film could be activated by a bakeout so as to transform the coated vacuum chamber into a pump. The materials studied so far are Ti, Zr, Hf, and some of their binary alloys. They all display an activation temperature lower than 400 degrees C, i.e., within the reach of the baking temperature of stainless steel vacuum chambers. The lowest activation temperature of 200-250 degrees C, measured for an equiatomic alloy of Ti and Zr, allows extension of this method to chambers made of copper and aluminum alloys. The experimental results, described here in detail, indicate that the values of the activation temperature obtained using electron stimulated desorption, pumping speed, and Auger spectroscopy measurements are self-consistent. (C) 1998 American Vacuum Society.