Valence band and In-4d core level photoemission study of de-capped and ion-bombarded-annealed InAs(0Â 0Â 1) epitaxial surfaces

The (4 × 2) epitaxial InAs(0 0 1) surface grown by molecular beam epitaxy and subjected to different surface treatments, namely amorphous As-de-capping and ion-bombardment annealing (IBA), is investigated by high-resolution angular-resolved UV photoelectron spectroscopy. Both treatments produce a semiconducting surface, ruling out the presence of metallic In aggregates. Binding energy shifts of 0.2-0.3 eV are measured for the valence-band levels of the IBA surface with respect to the de-capped surface, implying an important influence of the surface treatment on the subsurface region. The line-shape of the In-4d core levels, which consists of two different In-related surface doublets, is discussed in view of the recently proposed structural models based on dimers formation.