Surface defects and bulk defect migration produced by ion bombardment of Si(001)

Variable-temperature scanning tunneling microscopy is used to characterize surface defects created by 4.5 keV He ion bombardment of Si(001) at 80–294 K; surface defects are created directly by ion bombardment and by diffusion of bulk defects to the surface. The heights and areal densities of adatoms, dimers, and adatom clusters at 80 and 130 K are approximately independent of temperature and in reasonable agreement with molecular dynamics calculations of adatom production. At 180 K, the areal density of these surface features is enhanced by a factor of ˜3. This experimental result is explained by the migration and surface trapping of bulk interstitials formed within ˜2 nm of the surface.