Surface analysis and pumping speed measurements of oxygen-free palladium/titanium nonevaporable getter after heating at 100–450 °C

Abstract

A novel nonevaporable getter (NEG) consisting of an oxygen-free thin film of Ti covered with a thin film of Pd (oxygen-free Pd/Ti) with an activation temperature of 133 °C has recently been developed [T. Miyazawa et al., J. Vac. Sci. Technol. A 36, 051601 (2018)]. When activated by baking at 150 °C, an NEG pump using oxygen-free Pd/Ti evacuates H2 and CO efficiently at room temperature, and its pumping speeds for H2 and CO do not decrease even after repeated cycles of activation and exposure to the air [T. Kikuchi et al., AIP Conf. Proc. 2054, 060046 (2019)]. However, oxygen-free Pd/Ti does not evacuate other major residual gases, such as H2O or CO2. To expand the range of applications of the NEG, the authors analyzed the surface chemical composition of the oxygen-free Pd/Ti by synchrotron-radiation x-ray photoelectron spectroscopy after heating at various temperatures in the range of 100–450 °C for 10 min. The authors found that Ti segregated to the surface after heating at 300 °C for 10 min. In addition, the pumping speeds for H2 and CO of a vacuum vessel coated with oxygen-free Pd/Ti were measured after baking at various temperatures in the range of 150–400 °C for 12 h. These results suggested that Ti segregates to the Pd surface after baking at 250 °C for 12 h. Therefore, after heating above 250–300 °C, oxygen-free Pd/Ti can be used as an NEG pump for vacuum systems where active residual gases other than H2 and CO must be pumped.A novel nonevaporable getter (NEG) consisting of an oxygen-free thin film of Ti covered with a thin film of Pd (oxygen-free Pd/Ti) with an activation temperature of 133 °C has recently been developed [T. Miyazawa et al., J. Vac. Sci. Technol. A 36, 051601 (2018)]. When activated by baking at 150 °C, an NEG pump using oxygen-free Pd/Ti evacuates H2 and CO efficiently at room temperature, and its pumping speeds for H2 and CO do not decrease even after repeated cycles of activation and exposure to the air [T. Kikuchi et al., AIP Conf. Proc. 2054, 060046 (2019)]. However, oxygen-free Pd/Ti does not evacuate other major residual gases, such as H2O or CO2. To expand the range of applications of the NEG, the authors analyzed the surface chemical composition of the oxygen-free Pd/Ti by synchrotron-radiation x-ray photoelectron spectroscopy after heating at various temperatures in the range of 100–450 °C for 10 min. The authors found that Ti segregated to the surface after heating at 300 °C for 10 min. In addition...