Tip size effect on the appearance of a STM image for complex surfaces: Theory versus experiment for Si(111)-(7x7)

Scanning tunneling microscopy experiment and first-principles total energy calculation are combined to determine STM images for Si(111)-7x7 to resolve the long-time discrepancy between theory and experiment. Our experiment resolves clearly and simultaneously the rest and adatom spots, in good agreement with theory, with the rest atom spots almost as bright as those of the central adatoms in the unfaulted-half of the unit cells. Theoretical study suggests that a geometric hindrance effect due to finite tip size could be responsible for the past experimental inability to observe the rest atoms.