Reactions of Atomic Hydrogen with the Hydroxide- and Amine-Functionalized Si(100)-2x1 Surfaces: Accurate Modeling of Hydrogen Abstraction Reactions Using Density Functional Theory

Reactions of atomic hydrogen with the hydroxide- or amine-functionalized Si(100)-(2x1) surface provide a possible way of fabricating ultrathin layers of silicon oxide or silicon nitride. Modeling such radical reactions with popular density functionals such as B3LYP is known to have significant deficiencies. The M06 class of hybrid meta-density functionals presents a possible route to model these systems accurately. We have evaluated M06 for hydrogen abstraction reactions involving main group elements and compared the results to those from B3LYP and CCSD(T)//MP2 methods. M06 offers excellent efficiency and accuracy with a mean absolute deviation from CCSD(T) for hydrogen abstraction barriers of 1.3 kcal/mol as compared to 3.4 kcal/mol for B3LYP. Having established its accuracy, the M06 functional is subsequently used to understand atomic hydrogen-induced silicon oxide and silicon nitride layer formation, focusing on the dominant pathways for insertion into the silicon lattice's uppermost layer. For oxygen, our results indicate that atomic hydrogen will preferentially abstract the surface silicon monohydride, subsequently leading to oxygen insertion into the dimer bond. In contrast, the corresponding reactions for nitrogen do not result in selectivity for insertion.