Department of Mechanical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan.
J Phys Chem A. 2010 Jan 14;114(1):633-9. doi: 10.1021/jp908222g.
The reactions of hydrogen atom with silane and disilane are relevant to the understanding of catalytic chemical vapor deposition (Cat-CVD) and plasma enhanced chemical vapor deposition (PECVD) processes. In the present study, these reactions have been investigated by means of ab initio molecular-orbital and transition-state theory calculations. In both reactions, the most favorable pathway was found to be the H abstraction leading to the formation of SiH(3) and Si(2)H(5) products, with 5.1 and 4.0 kca/mol barriers, respectively. For H + Si(2)H(6), another possible reaction pathway giving SiH(3) + SiH(4) may take place with two different mechanisms with 4.3 and 6.7 kcal/mol barriers for H-atom attacking side-way and end-on, respectively. To validate the calculated energies of the reactions, two isodesmic reactions, SiH(3)+CH(4)-->SiH(4)+CH(3) and Si(2)H(5)+C(2)H(6)-->Si(2)H(6)+C(2)H(5) were employed; the predicted heats of the formation for SiH(3) (49.0 kcal/mol) and Si(2)H(5) (58.6 kcal/mol) were found to agree well with the experimental data. Finally, rate constants for both H-abstraction reactions predicted in the range of 290-2500 K agree well with experimental data. The result also shows that H+Si(2)H(6) producing H(2)+Si(2)H(5) is more favorable than SiH(3)+SiH(4.).
氢原子与硅烷和二硅烷的反应与催化化学气相沉积（Cat-CVD）和等离子体增强化学气相沉积（PECVD）过程的理解有关。在本研究中，通过从头算分子轨道和过渡态理论计算研究了这些反应。在这两个反应中，最有利的途径是 H 原子的抽取，导致 SiH(3)和 Si(2)H(5)产物的形成，分别具有 5.1 和 4.0 kcal/mol 的势垒。对于 H + Si(2)H(6)，另一种可能的反应途径可能通过两种不同的机制发生，H 原子侧攻和端攻的势垒分别为 4.3 和 6.7 kcal/mol。为了验证反应计算出的能量，采用了两个等电子反应 SiH(3)+CH(4)-->SiH(4)+CH(3)和 Si(2)H(5)+C(2)H(6)-->Si(2)H(6)+C(2)H(5)；SiH(3)（49.0 kcal/mol）和 Si(2)H(5)（58.6 kcal/mol）的生成热预测值与实验数据吻合较好。最后，在 290-2500 K 的范围内预测的两个 H 原子抽取反应的速率常数与实验数据吻合较好。结果还表明，H+Si(2)H(6)生成 H(2)+Si(2)H(5)比 SiH(3)+SiH(4)更有利。
