Chemical reactions and adsorption geometries of pyrrole on Ge(100)

Abstract

The adsorption structures of pyrrole ($C_4H_5N$) on the Ge(lOO) surface at various coverages have been investigated by scanning tunneling microscopy (STM). Pyrrole molecule binds to a on Ge-Ge dimer via Ge-N covalent linkage through the dissociation of N-H or α-C-H bond. However, if there is pre-adsorbed H atoms on the Ge(lOO) surface, the dissociated H atom is likely to adsorb on the neighboring Ge dimer atom where the pre-adsorbed H atoms located and thus the H-dissociated pyrrole binds to the adjacent Ge dimer of the doubly H-occupied dimer. In addition, we may conclude that the H-dissociated pyrrole diffuses toward the stable adsorption site after N-H or α-C-H bond dissociation. Among the adsorption geometries, N-end-on configuration induced by the N-H dissociation is dominant above 0.1 ML. At the saturation coverage, the pyrrole molecules bind to every dimer to form a ordered P(2\times2) structure.