PHOTOEMISSION-STUDIES OF THE INTERACTIONS OF CDTE AND TE WITH SI(100)

The interactions between CdTe, and in particular Te, and the (100) sur face of Si have been probed using photoemission and low energy electro n diffraction with a view to investigating the mechanisms responsible for (100) and (111) growth orientations for CdTe on Si(100). The inter facial reactions have been studied both on room temperature deposition followed by annealing and on depositions at typical epitaxial growth temperatures. In both cases the same precursor stage of an ordered sub monolayer of Te on the Si(100) surface has been identified. Line shape analysis of the Si 2p core level has suggested a structural model in which Te adatoms make up an incomplete monolayer bound in bridge sites , This model is in excellent agreement both with the (1 x 1) LEED patt ern and recent SEXAFS studies of this surface. The implications of the cubic symmetry of this surface in terms of the subsequent growth orie ntation of CdTe are discussed. Termination of the surface by Te was al so seen to induce band bending suggestive of Fermi level pinning at ar ound midgap, in contrast to the passivating behaviour of other group V I elements on this surface. The Si 2p core level line shape analysis o n termination by Te has also provided evidence to support the ''covale nt dimer'' interpretation of the clean dimerised Si(100) surface.