Process Optimization and Performance Study of Pd/Ti Getter Films Prepared by Ultra-High Vacuum Evaporation Coating

As an important vacuum-sustaining material in ultra-high vacuum systems, the Pd/Ti getter film offers advantages such as a low activation temperature and a fast pumping speed. Targeting the bending deformation problem of traditional evaporation sources caused by thermal expansion during heating, COMSOL Multiphysics simulation was employed to analyze the thermal deformation behavior of target wires. A composite structure design of "quartz glass rod + variable-pitch spring target wire" was proposed, reducing the maximum radial thermal deformation of Pd wire and Ti wire to 0.0216 mm and 0.0494 mm respectively, representing improvements of approximately 303 times and 63 times compared to straight wire structures. An ultra-high vacuum evaporation coating system was independently designed and constructed, and the evaporation process parameters of Pd-Ti films were systematically studied, determining optimal conditions of Ti wire at 45 A/60 min and Pd wire at 18 A/2-10 min. SEM analysis revealed the typical columnar growth structure of the films, with continuous and uniform Pd overlayer coverage on the Ti underlayer. The ultimate vacuum of the system after coating reached 1.41×10⁻⁸Pa, with significantly improved vacuum retention performance. Constant pressure hydrogen absorption tests showed that substrate materials significantly affect gettering performance, with oxygen-free copper foil substrate achieving a stable pumping speed (0.006 L/(s·cm²)) superior to industrial titanium foil substrate (0.002 L/(s·cm²)). An optimal Pd layer thickness exists, with approximately 50 nm thickness showing the best gettering performance and pumping speed of 0.005 L/(s·cm²). This study provides important technical support and data foundation for the engineering preparation of Pd-Ti film getters.