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

Abstract

The chemisorption and decomposition of pyrrole (C 4H 4NH) 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 C 4H 4NH occurs readily on either the adatom site (Si a) or the rest atom site (Si r), giving rise to C 4H 4N and H adspecies, and forming N adsP a and N adsP r products respectively. The calculations showed that the C α 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.