Chemisorption of pyrrole (C4H4NH) on Si(0 0 1) calculated from first-principles

First-principles pseudopotential calculations for a large number of C4H4NH/Si(0 0 1) adsorption configurations possibly resulting from reactions such as [2 + 2] or [4 + 2] cycloadditions are presented. Energetically most favorable are dissociative reactions, leading to the partial fragmentation of the molecule. The lowest energy configuration for monolayer coverage is characterized by pyrrole rings bonded to the surface via Si–N linkage. In co-existence with adsorption geometries where both N and C are bonded to the surface, this structure accounts very well for the available experimental data.