Oxygen-free palladium/titanium coating, a novel nonevaporable getter coating with an activation temperature of 133 °C

A novel nonevaporable getter (NEG) coating was developed with an activation temperature as low as 133 degrees C, that is, a palladium/titanium coating with extremely low oxygen concentration (oxygen-free Pd/Ti coating). The substrate was coated with Ti and then overcoated with Pd using sublimation under ultrahigh vacuum conditions. The morphology and surface elemental composition of the Pd/Ti thin film were investigated with electron microscopes and x-ray photoelectron spectroscopy, respectively. The thicknesses of Ti and Pd films were approximately 1.3 mu m and 50 nm, and the Ti film was completely overcoated by the Pd film. Ti and oxygen were found to be negligible on the oxygen-free Pd/Ti surface. The oxygen-free Pd/Ti coating was applied to the formed bellows. The bellows was successively baked at 133 degrees C for 12 h, 176 degrees C for 3.5 h, and 200 degrees C for 3.5 h. After sealing off a turbomolecular pump from the vacuum system containing the bellows, the pressure reached values of 4.6 x 10(-6), 1.7 x 10(-7), and 6.1 x 10(-8) Pa, respectively. The pumping speeds of the bellows were estimated to be 0.028, 0.23, and 0.23 1 s(-1), respectively. These results demonstrate that oxygen-free Pd/Ti deposition can be used as a new NEG coating for vacuum systems with a baking temperature of 133 degrees C or higher. Published by the AVS.