Different Crystal Growth Mechanisms of Si(001)-(2 × 1):H during Plasma-Enhanced Chemical Vapor Deposition of SiH3 and SiH2 Radicals: Tight-Binding Quantum Chemical Molecular Dynamics Simulations

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We use tight-binding quantum chemical molecular dynamics to investigate the crystal growth mechanisms of H-terminated Si(001)-(2 × 1) during plasma-enhanced chemical vapor deposition of SiH3 and SiH2 radicals. We find that crystal growth by SiH3 radical deposition consists of two stages: (1) the first SiH3 radical abstracts a surface-terminating H atom and produces a dangling bond, and (2) a second SiH3 radical is adsorbed on the dangling bond. Thus, at least two SiH3 radicals are required for generating a new Si–Si bond. Interestingly, during SiH2 deposition, a SiH2 radical can be directly adsorbed onto a H-terminated site without H abstraction by another SiH2 radical. Thus, one SiH2 radical is sufficient for generating a new Si–Si bond. This SiH2 radical crystal growth mechanism is different from the SiH3 radical mechanism. The direct adsorption process consists of a two-step chemical reaction: (1) the SiH2 radical abstracts a surface-terminating H atom and produces a dangling bond and a SiH3 radical, a...