Vacancy trapping behaviors of hydrogen near ruthenium by A first principles method

Hydrogen (H) damage dominates the lifetime of ruthenium (Ru) films on multilayer mirrors, where vacancy trapping of H atoms is critical to its formation. In this paper, the effect of vacancy on the trapping behavior of H atoms is studied using first principles calculations. It was found that the H atom exhibits high diffusivity towards the vacancy, owing to the strong attractive interaction between them. Notably, a single vacancy can accommodate up to nine H atoms and they tend to stabilize on the equivalent surface with identical charge density at the vacancy of Ru. Furthermore, electronic structure analysis reveals that when multiple H atoms are located near the vacancy site, center two H atoms can form molecules by sharing electrons, it may lead to the H bubble formation. This work provides a theoretical guidance for understanding the formation mechanism of vacancy induced H damage in multilayer mirrors.