First-principles study on mixed SimNn (m+n=2–9) clusters

Detection of Two Highly Stable Silicon Nitrides: HSiNSi and H3SiNSi

“…Detection of two small unexpected silicon nitrides at such high abundance suggests that new formation pathways in the synthesis of larger Si–N species may have to be considered. Theoretical calculations of silicon–nitrogen clusters of a wide range of sizes and compositions , suggest that as the cluster size increases, the favored structures are planar or cage-like with alternating Si–N bonds and that for clusters of a given size, those with nearly equal numbers of silicon and nitrogen atoms are the most stable. Models of Si 3 N 4 formation in CVD processes have generally emphasized insertion of either SiH 4 or its thermal decomposition product SiH 2 (or chlorinated derivatives, if applicable) into the N–H bonds of ammonia, ,,− yielding aminosilane (H 3 SiNH 2 ) or an aminochlorosilane (e.g., HCl 2 SiNH 2 ).…”

“…Fairly recently, the use of films of silicon nitride with hydrogen (SiN x /H) as antireflective coatings and passivation layers in silicon-based solar cells has become common. − Electronic-grade silicon nitride films are most commonly formed using chemical vapor deposition (CVD), or one of its variants, in which gaseous silane or a chlorosilane (such as SiCl 4 ) reacts with ammonia to form solid Si 3 N 4 ; SiN x /H films are most often grown using plasma-enhanced CVD (PECVD) from mixtures of silane and either nitrogen or ammonia. For these reasons, theoretical and experimental attention has focused on the structure and properties of small, gaseous silicon–nitrogen clusters, − but the role that specific clusters play in CVD reaction pathways is unclear, particularly as the formation may involve surface reactions in addition to gas-phase chemistry. Efforts to model film growth from CVD processes in some cases have ignored gas-phase chemistry entirely or focused only on the formation of the first silicon–nitrogen bond via gas-phase chemistry. , Studies that include both gas-phase and surface reactions , have been highly empirical in nature, establishing correlations between physical and chemical starting conditions and film properties rather than examining detailed chemical mechanisms.…”