Abstraction of hydrogen by SiH₃ from hydrogen-terminated Si(001)-(2 × 1) surfaces

We present the dynamics and energetics of an Eley-Rideal reaction by which SiH₃ radicals impinging on a H-terminated Si(001)-(2 × 1) surface during plasma deposition abstract hydrogen atoms from the surface and return to the gas phase as silane molecules. The reactions were observed during classical molecular-dynamics simulations of hydrogenated amorphous silicon deposition from SiH₃ radicals impinging on H-terminated Si(001)-(2 × 1) surfaces maintained at temperatures over the range 500 K ≤ T ≤ 773 K. The H-abstraction reaction introduces dangling bonds at the surface that impinging SiH_x (0 ≤ × ≤ 3) radicals can attach to; thus, it is a crucial reaction for deposition. The computed activation energy barrier for the reaction and the exothermic reaction energy are 0.09 eV and 0.23 eV, respectively. The energetics of the reaction as computed based on an empirical classical potential are in good agreement with density-functional-theory pseudopotential calculations using a cluster model.