Atomic layer deposition (ALD) of
ruthenium using two ruthenium
precursors, i.e., Ru(C<sub>5</sub>H<sub>5</sub>)<sub>2</sub> (RuCp<sub>2</sub>) and Ru(C<sub>5</sub>H<sub>5</sub>)(C<sub>4</sub>H<sub>4</sub>N) (RuCpPy), is studied using density functional theory. By investigating
the reaction mechanisms on bare ruthenium surfaces, i.e., (001), (101),
and (100), and H-terminated surfaces, an atomistic insight in the
Ru ALD is provided. The calculated results show that on the Ru surfaces
both RuCp<sub>2</sub> and RuCpPy can undergo dehydrogenation and ligand
dissociation reactions. RuCpPy is more reactive than RuCp<sub>2</sub>. By forming a strong bond between N of Py and Ru of the surface,
RuCpPy can easily chemisorb on the surfaces. The reactions of RuCp<sub>2</sub> on the surfaces are less favorable as the adsorption is not
strong enough. This could be a factor contributing to the higher growth-per-cycle
of Ru using RuCpPy, as observed experimentally. By studying the adsorption
on H-terminated Ru surfaces, we showed that H can prevent the adsorption
of the precursors, thus inhibiting the growth of Ru. Our calculations
indicate that the H content on the surface can have an impact on the
growth-per-cycle. Finally, our simulations also demonstrate large
impacts of the surface structure on the reaction mechanisms. Of the
three surfaces, the (100) surface, which is the less stable and has
a zigzag surface structure, is also the most reactive one
