X-RAY STRUCTURAL STUDIES OF EPITAXIAL YTTRIUM SILICIDE ON SI(111)

We performed a series of glancing angle and reflection x-ray diffracti on experiments to study both the in-plane and out-of-plane structure o f epitaxial YSi2-x films grown on Si(111), with thicknesses ranging fr om 85 angstrom to 510 angstrom. These measurements allowed us to chara cterize the mean film lattice constants, the position correlation leng ths of the film, and the presence and extent of strain as a function o f film thickness. We find that the strain along the basal plane increa ses as a function of increasing thickness to approximately 1% in the 5 10 angstrom film; the corresponding out-of-plane strain is such that t he film unit cell volume increases as a function of thickness. The cor responding in-plane microscopic strain varies from 0.5% for the 85 ang strom film to 0.3% for the 510 angstrom film. We relate our results to the mode of film growth and the presence of pinholes in the films.