A PHOTOEMISSION-STUDY OF ERBIUM SILICIDE ULTRA-THIN FILMS EPITAXIALLY GROWN ON SI(111)

We have investigated the growth and the electronic structure of ultra-thin (0.2 to 6 ML) Er films deposited at room temperature on a Si(111)7 x 7 surface and subsequently annealed to 600-degrees-C using LEED, ARUPS, AES and XPS. Our aim was to study the early stages of the (epitaxial) erbium silicide/Si(111) interface formation. We have found two different regimes: In the submonolayer range, OUT data indicate the growth of two-dimensional islands having a (1 x 1) symmetry. The band structure of this phase has been mapped. Above 1 ML, the film surface shows an asymmetric square-root 3 x square-root 3 R30-degrees superstructure. The ARUPS spectra rapidly evolve towards those of thick silicide layers, although some differences remain clearly observable close to the GAMMA point. These results - complemented with AES and XPS data - will be discussed in relation with our present knowledge of the erbium silicide structure.