Photoemission study of monolayer Co on Si(111) surface

The interaction of monolayer Co with the Si(lll) surface is investigated by means of core-level and valence-band photoemission spectroscopy in the ran ge of room temperature to 700 degrees C. Upon increasing the annealing temp erature, several formations of silicides are observed. This ultra-thin laye r upon annealing at 300-400 degrees C has electronic structure closely rela ted to the metastable CsCl-type CoSi which was discovered by molecular beam epitaxy (MBE) grown onto the CoSi, template to a thickness of similar to 1 00 Angstrom. Further annealing up to 500 degrees C leads to the epsilon-CoS i-type electronic structure. Finally, the formation of CaF2-type CoSi2 is o bserved after annealing above 600 degrees C. They lead also to an island fo rmation above 700 degrees C. (C) 1999 Elsevier Science B.V. All rights rese rved.