Reactive molecular dynamic simulations of hydrogenation process of amorphous silicon nitride

摘要

Hydrogenated amorphous silicon nitride is useful as an anti-reflection coating on solar cells. The addition of hydrogen atoms to amorphous silicon nitride can reduce the dangling bonds that exist on the surface. The objective of this paper is to clarify on the behavior of hydrogen atoms absorbed in silicon nitride during the hydrogenation process at various temperatures. We investigate, in particular, the silicon and hydrogen bonds that are formed by the transfer of electrons from hydrogen to silicon to form Si1?, Si2?, Si3?, and Si4? ions. The conversion of Si1? ions into Si2? ions and then also into Si3? and Si4? occurs during enhancement of the hydrogen atoms absorbed. Hydrogenated amorphous silicon nitride was stabilized through the passivation of dangling bonds of silicon atoms and nitrogen atoms by the absorbed hydrogen atoms. The passivation was indicated by enhancement of over-coordinated silicon and nitrogen atoms as well as the reduction of under-coordinated silicon and nitrogen atoms. It was found that the thermal energy from high hydrogenation temperature was primarily used by hydrogen atoms to diffuse more and to penetrate deeper into silicon nitride rather than being used for the ionization of silicon atoms. Finally, we stress that these reactive molecular dynamic simulations have led to substantial progress in understanding how hydrogen atoms interact with amorphous silicon nitride during hydrogenation.