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Ab Initio Chemical Kinetics for SiH x Reactions with Si 2 H y ( x = 1,2,3,4; y = 6,5,4,3; x + y = 7) under a‐Si:H CVD Condition
Author(s) -
Nguyen TrongNghia,
Lin M. C.
Publication year - 2017
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.21067
Subject(s) - chemistry , ab initio , rrkm theory , reaction rate constant , radical , atmospheric temperature range , standard enthalpy of formation , excited state , chemical vapor deposition , potential energy surface , computational chemistry , kinetics , thermodynamics , atomic physics , physics , organic chemistry , quantum mechanics
Gas‐phase reactions of SiH x with Si 2 H y ( x = 1,2,3,4; y = 6,5,4,3) species, respectively, which may coexist under chemical vapor deposition (CVD) conditions, have been investigated by means of ab initio molecular orbital and statistical theory calculations. Potential energy surface (PES) predicted at the CCSD(T)/CBS//B3LYP/6–311++G(3df,2p) level shows that these reactions take place primarily via trisilany radicals, n ‐Si 3 H 7 and i ‐Si 3 H 7 . For example, SiH 2 can associate with Si 2 H 5 producing n ‐H 2 SiSiH 2 SiH 3 exothermically by 55.8 kcal/mol; SiH 3 can undergo addition to H 2 SiSiH 2 to produce n ‐Si 3 H 7 or associate with H 3 SiSiH barrierlessly forming i ‐Si 3 H 7 ; whereas SiH can insert into one of the Si─H bonds of Si 2 H 6 to give excited n ‐Si 3 H 7 . Similarly, H 2 SiSiH and SiSiH 3 can undergo insertion reactions with SiH 4 producing n / i ‐Si 3 H 7 intermediates, respectively, to be followed by fragmentation to various smaller species. These processes are fully depicted in the complete PES. The predicted heats of formation of various species agree well with available thermochemical data. The rate constants and product branching ratios for the low‐energy channel products have been calculated for the temperature range 300–1000 K by variational RRKM (Rice–Ramsperger–Kassel–Macus) theory with Eckart tunneling corrections. The results may be employed for realistic kinetic modeling of the plasma‐enhanced chemical vapor deposition growth of a‐Si:H thin films under practical conditions.