Ab Initio Chemical Kinetics for SiH_xReactions with Si₂H_y(x= 1,2,3,4;y= 6,5,4,3;x+y= 7) under a-Si:H CVD Condition

Abstract

Gas‐phase reactions of SiHx with Si2Hy (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‐Si3H7 and i‐Si3H7. For example, SiH2 can associate with Si2H5 producing n‐H2SiSiH2SiH3 exothermically by 55.8 kcal/mol; SiH3 can undergo addition to H2SiSiH2 to produce n‐Si3H7 or associate with H3SiSiH barrierlessly forming i‐Si3H7; whereas SiH can insert into one of the Si─H bonds of Si2H6 to give excited n‐Si3H7. Similarly, H2SiSiH and SiSiH3 can undergo insertion reactions with SiH4 producing n/i‐Si3H7 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.

Ideal gas thermochemical properties of silicon containing inorganic, organic compounds, radicals, and ions

“…Si 2 H 5 Si 2 H 5 ‐ Disilanyl and anion SiH 3 ‐SiH 2 * . The radical is experimentally measured by Ruscic and Berkowitz Δ f H °(0 K) < 264.8 kJ mol −1 , and a less well defined value of 247.7 kJ mol −1 is given which is nearer to the calculated value by Nguyen and Lin Δ f H °(0 K) = 248.9 kJ mol −1 . The G3B3 present calculation reads Δ f H °(298 K) = 227.2 ± 8 kJ mol −1 and Δ f H °(0 K) = 239.9 ± 8 kJ mol −1 .…”

“…calculated Δ f H °(298 K) = 318.8 kJ mol −1 , Broadbelt and coworkers calculated Δ f H °(298 K) = 306.7 kJ mol −1 , Sukkaew et al . report Δ f H °(298 K) = 305.1‐303.1 kJ mol −1 , and Nguyen and Lin using the CCSD(T) method list Δ f H °(0 K) = 323.8 kJ mol −1 The present G3B3 calculation lists Δ f H °(298 K) = 304.2 ± 8 kJ mol −1 and Δ f H °(0 K) = 312.8 ± 8 kJ mol −1 .…”

“…calculated Δ f H °(298 K) = 274.8 kJ mol −1 ; Ragunath and Lin report Δ f H °(0 K) = 287.4 ± 4.2 kJ mol −1 . Nguyen and Lin using the CCSD(T) method list Δ f H °(0 K) = 288,7 kJ mol −1 . The G3B3 value is Δ f H °(298 K) = 262.4 ± 8 kJ mol −1 (Δ f H °(0 K) = 280.1 ± 8 kJ mol −1 ).…”

“…Sukkaew et al 18 calculated some Si-C-H compounds. And finally Lin and coworkers [19][20][21][22][23] published in 2013-2017 articles about SiH x and Si 2 H y family including some cations.…”

Electronic structure of the ground and excited states of neutral and charged silicon hydrides, SiHx0/+/−, x = 1–4

“…Silicon nanoparticle formation under plasma conditions is governed by reactions between cations, anions, and neutral molecules. 1–7 Under low-pressure non-thermal plasma conditions, three dominant phenomena include particle nucleation, particle surface growth, and coagulation. The study herein will focus on particle nucleation and growth involving the formation of small clusters, which is dominated by reactions between anions and neutral molecules or radicals.…”