Electronic structure of Si(111) surfaces

The relation of surface states and surface core levels to the surface geometry is discussed for Si(111) surfaces by comparing photoemission and inverse photoemission results with calculations for different geometries. It is shown that several sets of recent angle-resolved photoemission data for Si(111)-(2 × 1) and Si(111)-(7 × 7) are very similar to each other despite the fact that they have been interpreted in terms of different geometries. This indicates that no unique conclusions about the surface geometry can be drawn from the surface electronic structure. At present, only the traditional ionic buckling models can be ruled out rather safely. New information about unoccupied urface states in the gap of Si(111)-(7 × 7) is obtained from inverse photoemission data. The quenching behavior of occupied surface states under hydrogen exposure shows an unexpected band narrowing which helps identify the origin of surface state bands from the energy level of a localized state at 0.2 eV below the valence band maximum. © 1983.