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, Si2H4, SiH3, and SiH2 on the Si(100)-(2 × 1) surface were predicted. It was found that Si2H5, Si2H4, 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 Si2H4(a), SiH3(a), SiH2(a), and H(a) without any thermal activation, and the decomposition of Si(100)/Si2H5(a) → Si2H4(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 Si2H5(a) + H(a) → 2SiH3(a) with an exothermicity of 2.3 kcal/mol by passing a barrier of 59.9 kcal/mol.