Insights into the Nature of SiH_4-BH_3 Complex: theoretical Investigation of New Mechanistic Pathways Involving SiH_3~· and BH_4~· Radicals

摘要

We have investigated a new type of interaction between silane (SiH_4) and borane (BH_3) using high level ab initio calculations. The SiH_4-BH_3 complex is found to be extremely stable with the formation of a bridged hydrogen bond betweenSiH_4 and BH_3. Hence, it might have a hitherto unknown role in the mechanism of chemical vapor deposition (CVD), which is employed in the fabrication of boron doped silicon semiconductor materials. In an attempt to unravel this role and the underlying reasons responsible for the stability of this complex, we have carried out a detailed analysis base don the structure and molecular orbitals. The results indicate that the binding strength and electronic character of the bridged hydrogen bond in the SiH_4-BH_3 complex is between those observed in double hydrogen bridged B_2H_6 and mono-hydrogen bridged anion B_2H_7~-. In contrast to B_2H_6 and B_2H_7~-, it should be noted that the complex is stabilized by direct strong electrostatic interaction between the positively charged Si atom and the negatively charged B atom as well as by monobridged hydrogen bonding. Furthermore, we also note that the SiH_4-BH_3 complex would dissociate to form SiH_3~·and BH_4~· radicals. The existence of this complex is also inferred from good agreement between the calculated IR spectra and experimentally observed spectra of thin solid films of boron doped silicon semiconductor materials.