Mechanisms for pyrrole adsorption on the Si(1 1 1)7 × 7 surface: A DFT cluster model study

The chemisorption and decomposition of pyrrole (C4H4NH) on the reconstructed Si(1 1 1)7 × 7 surface have been investigated by means of hybrid density functional B3LYP method in combination with the cluster model approach. Three chemisorption mechanisms, N-H dissociative adsorption, [4 + 2] cycloaddition, C-H and N-H dissociative adsorption of pyrrole onto a rest atom-adatom pair site, have been considered comparatively. It is shown that the dissociaton of C4H4NH occurs readily on either the adatom site (Sia) or the rest atom site (Sir), giving rise to C4H4N and H adspecies, and forming NadsPa and NadsPr products respectively. The calculations showed that the Cα adsorption process is barrierless and favorable over the N adsorption one. Through compare and analysis the three chemisorption mechanisms, N-H dissociative adsorption on a rest atom-adatom pair of the Si(1 1 1)7 × 7 surface is the most favorable, whereas C-H and N-H dissociative adsorption on a rest atom-adatom pair is the most difficult.