Computational Study for Reactions of H Atoms with Adsorbed SiH<sub>3</sub> and Si<sub>2</sub>H<sub>5</sub> on H‑Covered Si(100)-(2 × 1) Surface

2014-09-04T00:00:00Z (GMT) by Hsin-Tsung Chen Hsien-Wei Huang
Density functional theory calculations with spin-polarization effect were employed to illustrate the adsorption of Si<sub><i>x</i></sub>H<sub><i>y</i></sub> (<i>x</i> = 1–2; <i>y</i> = 1–5) species and the reactions of H atoms with adsorbed SiH<sub><i>x</i></sub> (<i>x</i> = 1–3) and Si<sub>2</sub>H<sub>5</sub> species on the H-covered Si(100)-(2 × 1) surface. The configurations and energies of these adsorbates were elucidated. It was found that H vacancy sites can be easy created by SiH<sub>3</sub> and Si<sub>2</sub>H<sub>5</sub> radicals with small barriers (2.1 and 1.6 kcal/mol for SiH<sub>3</sub> and Si<sub>2</sub>H<sub>5</sub>, respectively). The Si<sub>2</sub>H<sub>5</sub>, Si<sub>2</sub>H<sub>4</sub>, SiHSiH<sub>3</sub>, SiH<sub>3</sub>, SiH<sub>2</sub>, SiH, and Si radials interact with the surface more forcefully than the Si<sub>2</sub>H<sub>6</sub> and SiH<sub>4</sub> molecules. Potential energy surfaces for the reaction mechanisms of H + SiH<sub><i>x</i></sub>(a) and H + Si<sub>2</sub>H<sub>5</sub>(a) were mapped by using the nudged elastic band method. The calculation results demonstrate that the most favorable pathway is hydrogen abstraction leading to the production of H<sub>2</sub> and Si<sub><i>x</i></sub>H<sub><i>y</i></sub> (<i>x</i> = 1–2; <i>y</i> = 0–4) because of their low barriers and high exothermicities. Rate constant calculations were performed to study the kinetic behavior for simulation of silicon thin-film growth by chemical vapor deposition processes.