Adsorption and reaction of Si₂H₅ on clean and H-covered Si(100)-(2 × 1) surfaces: A computational study

A spin-polarized density functional theory calculation was carried out to characterize the adsorption and decomposition of Si₂H₅ radical on the clean and H-covered Si(100)-(2 × 1) surface. The adsorption structures and energies of Si₂H₅, Si₂H ₄, SiH₃, and SiH₂ on the Si(100)-(2 × 1) surface were predicted. It was found that Si₂H₅, Si ₂H₄, SiH₃, and SiH₂ preferentially adsorb at the dimer-a, intrarow, dimer-b, and in-dimer sites, respectively. Potential energy profiles for the reactions of Si₂H₅ radical on the clean and H-covered Si(100)-(2 × 1) surfaces were constructed using the nudged elastic band (NEB) method. Calculations show that the Si₂H₅ radical can easily decompose to Si ₂H_4(a), SiH_3(a), SiH_2(a), and H _(a) without any thermal activation, and the decomposition of Si(100)/Si₂H_5(a) → Si₂H _4(a)/Si(100)/H_(a) may be the dominant mechanism on the clean Si(100) surface because of its low barrier and high exothermicity. The most likely mechanism for the reaction of Si₂H₅ on the H-covered Si(100)-(2 × 1) surface is the reaction of Si₂H _5(a) + H_(a) → 2SiH_3(a) with an exothermicity of 2.3 kcal/mol by passing a barrier of 59.9 kcal/mol.