Vacuum Pumping Performance Comparison of Non-Evaporable Getter Thin Films Deposited Using Argon and Krypton as Sputtering Gases

Owing to the outstanding vacuum performance and the low secondary electron yield, non-evaporable getter (NEG) thin film deposited onto interior walls has gained widespread acceptance and has been incorporated into many accelerator vacuum system designs. In this paper, the titanium-zirconium-vanadium NEG thin films were deposited onto interior wall of stainless pipes via DC magnetron sputtering method using argon and krypton gas respectively as the sputtering gas. Vacuum pumping evaluation tests were carried out to compare vacuum pumping performances of the Ti-Zr-V NEG thin films deposited using the two rare gases. The results showed much higher initial pumping speed for the Kr-sputtered NEG film than the Ar-sputtered film, though both films have similar activation behavior. Films were also deposited onto silicon wafers under the same experimental conditions, and Rutherford Backscattering Spectrometry (RBS) analysis was carried out to obtain information of the film composition and thickness. The RBS analysis showed that the concentration of argon is significantly higher that of krypton. Insight of the textures of both thin films will be pursued for better understanding of the cause of their difference in pumping performances.