Electronic structures of dangling-bond structures fabricated on hydrogen-terminated Si(100)-2 × 1 surfaces

Various atomic-scale dangling-bond (DB) structures were fabricated on a hydrogen-terminated Si(100)-2 × 1-H surface, and studied by using scanning tunneling microscopy/ spectroscopy (STM/STS). The DB structures, composed of various combinations of paired or unpaired DBs, were investigated both at room temperature and at low temperatures. It was found that the structures, made up only of paired DBs along a dimer row, exhibited semiconductive electronic states with a band gap of approximately 0.5eV Structures composed of both unpaired and paired DBs exhibited a finite density of states at the Fermi energy, while the surrounding hydrogen-terminated surface had a wide semiconductive band gap. On the basis of a first-principles study, it was concluded that DB structures have a density of states at the Fermi energy if the unpaired DBs and DB pairs are suitably mixed. In the case of DB structure made up only of unpaired DBs, charge redistribution was observed in the DB wire. The origins of these structural changes in the DB wires are also discussed.