On the primary process in the plasmahyphen;chemical and photochemical vapor deposition from silane. III. Mechanism of the radiative species Siast;(1Pthinsp;0) formation

摘要

The mechanism of the radiative species Siast;(1P0) formation from SiH4was investigated withabinitiomolecular orbitalndash;configuration interaction calculations on two reaction routes: (a) the simplest onehyphen;step reaction mechanism SiH4rarr;Si+2H2and (b) the second simplest twohyphen;step reaction mechanism SiH4rarr;SiH2+H2rarr;Si+2H2. The conclusions obtained are as follows: (i) the onehyphen;step mechanism (a) operates effectively in the generation of the radiative species Siast;(1P0), (ii) no effective path was found for the formation of Siast;(1P0) in the twohyphen;step mechanism, (iii) the radiative species Siast;(1P0) originates from the fifth lowest excited singlet state 11T1of SiH4at theTdstructure in the onehyphen;step mechanism (a), whereas the nonradiative species Si(1D) is produced spontaneously from the fourth lowest excited singlet state 11Ein both reaction mechanisms of (a) and (b), (iv) the nonradiative species SiH2(11B1) is spontaneously generated from the lowest excited singlet state 11T2of SiH4, (v) the electronic state of the radiative Siast;(1P0) has Rydberg character and the emission of Siast;(1P0) at 288.2 nm is approximately expressed by 3p4s(1P0)rarr;3p2(1D) where 4sis a Rydberg atomic orbital (AO). It was also concluded that the contributions of 3dAOs are important for making a description of the quantitative energy separations among the lower lying singlet states,1D,1S, and1P0of Si atoms.