Photoemission spectroscopy of ultrathin hydrogenated amorphous silicon films on silicon oxide show that the interfaces are atomically abrupt. The Si 3p valence band is already developed in monolayer-thick islands. The absence of quantum-size effects associated with holes indicates that the Si 3p wave functions are localized on a scale of a few angstroms. The range of the Si 2p core-hole–exciton interaction is estimated to be 6 Å.

• Received 29 December 1986

DOI:https://doi.org/10.1103/PhysRevB.35.9395