Si monomers are observed in empty-state scanning tunneling microscopy
images acquired between room temperature and 115 degrees C. The monome
rs are trapped at the ends of rebonded SE-type dimer rows. When monome
rs thermally escape from the traps, they rapidly diffuse along the sub
strate dimer row until they find another unoccupied trap or return to
their original trap. The binding activation barrier at isolated traps
is similar to 1.0 eV. A slightly lower barrier exists for monomers to
hop between the ends of neighboring dimer rows-a process facilitating
diffusion along segments of SE-type steps.