Dimer-vacancy–dimer-vacancy interaction on the Si(001) surface: The nature of the 2×nstructure

An increase of dimer vacancies on the Si(001)-2×{}1 surface after radiation quenching from high temperatures has been observed using STM. After further quenches, vacancies nucleate into chains running perpendicular to the dimer rows. These vacancy chains then connect and develop into vacancy lines (VL's) that extend for many thousands of {}. Each VL consists of mainly two types of dimer vacancies: a divacancy and the combination of a single vacancy and a divacancy separated by an isolated dimer. All the VL's together with the dimer rows form a 2×{}n structure with 6{≤}n{≤}12. Calculations using the Stillinger-Weber potential have been performed to examine the ordering mechanism of dimer vacancies.