Ab Initio Chemical Kinetics for the Thermal Decomposition of SiH₄ ⁺ Ion and Related Reverse Ion–Molecule Reactions of Interest to PECVD of a-Si:H Films

TY - JOUR

T1 - Ab Initio Chemical Kinetics for the Thermal Decomposition of SiH4 + Ion and Related Reverse Ion–Molecule Reactions of Interest to PECVD of a-Si:H Films

AU - Nguyen, T. N.

AU - Lee, Y. M.

AU - Wu, Jong-Shinn

AU - Lin, Ming-Chang

N1 - Publisher Copyright: © 2017, Springer Science+Business Media New York.

PY - 2017/7/1

Y1 - 2017/7/1

N2 - The thermal unimolecular decomposition of SiH4 + ion and its related reverse reactions, SiH3 + + H and SiH2 + + H2, have been investigated by ab initio molecular orbital and quantum statistical variational RRKM theory calculations. The potential energy surface has been calculated at different levels of theory; the results at the highest level, CCSD(T)/CBS//CCSD(T)/6-311++G(3df,2p), show that the decomposition of SiH4 + can mainly occur via a barrierless channel giving SiH2 + + H2 lying 11.8 kcal/mol above the reactant, or via a transition state forming SiH3 +···H complex to be followed by a barrierless decomposition yielding SiH3 + + H lying 23.5 kcal/mol above the reactant. Barrierless processes were calculated using the CASPT2 and CASSCF methods with the 6-311++G(3df,2p) basis set and fitted with Morse potentials. The rate constants were predicted by solving master equations based on the RRKM theory at the E,J-resolved level; the results show that the channel SiH4 + → SiH2 + + H2 is predominate under PEVCD conditions. For H- and H2-capturing by SiH3 + and SiH2 + ions, respectively, the rate constants were found to be weakly dependent on temperature at the high-pressure limit and decrease rapidly with pressure. The calculated heats of formation of the SiHx + (x = 2–4) ions are in close agreement with available thermochemical data.

AB - The thermal unimolecular decomposition of SiH4 + ion and its related reverse reactions, SiH3 + + H and SiH2 + + H2, have been investigated by ab initio molecular orbital and quantum statistical variational RRKM theory calculations. The potential energy surface has been calculated at different levels of theory; the results at the highest level, CCSD(T)/CBS//CCSD(T)/6-311++G(3df,2p), show that the decomposition of SiH4 + can mainly occur via a barrierless channel giving SiH2 + + H2 lying 11.8 kcal/mol above the reactant, or via a transition state forming SiH3 +···H complex to be followed by a barrierless decomposition yielding SiH3 + + H lying 23.5 kcal/mol above the reactant. Barrierless processes were calculated using the CASPT2 and CASSCF methods with the 6-311++G(3df,2p) basis set and fitted with Morse potentials. The rate constants were predicted by solving master equations based on the RRKM theory at the E,J-resolved level; the results show that the channel SiH4 + → SiH2 + + H2 is predominate under PEVCD conditions. For H- and H2-capturing by SiH3 + and SiH2 + ions, respectively, the rate constants were found to be weakly dependent on temperature at the high-pressure limit and decrease rapidly with pressure. The calculated heats of formation of the SiHx + (x = 2–4) ions are in close agreement with available thermochemical data.

KW - Kinetics

KW - Mechanism

KW - PECVD

KW - SiH

KW - Silicon thin film

UR - http://www.scopus.com/inward/record.url?scp=85020102653&partnerID=8YFLogxK

U2 - 10.1007/s11090-017-9825-7

DO - 10.1007/s11090-017-9825-7

M3 - Article

AN - SCOPUS:85020102653

SN - 0272-4324

VL - 37

SP - 1249

EP - 1264

JO - Plasma Chemistry and Plasma Processing

JF - Plasma Chemistry and Plasma Processing

IS - 4

ER -