STRUCTURAL STUDY OF YSI1.7 LAYERS FORMED BY CHANNELED ION-BEAM SYNTHESIS

High quality YSi1.7 layers (chi(min) of Y is 3.5%) have been formed by 60 keV Y ion implantation in Si (111) substrates to a dose of 1.0 x 1 0(17)/cm(2) at 450 degrees C using channeled ion beam synthesis (CIBS) . It shows that, compared to the conventional nonchanneled ion beam sy nthesis, CIBS is beneficial in forming YSi1.7 layers with better quali ty due to the lower defect density created in the implanted layer. Rut herford backscattering/channeling and x-ray diffraction have been used to study the structure and the strain of the YSi1.7 layers. The perpe ndicular and parallel elastic strains of the YSi1.7 epilayer are e(per pendicular to) = -0.67% +/- 0.02% and e(parallel to) = +1.04% +/- 0.08 %. The phenomenon that a nearly zero mismatch of the YSi1.7/Si (111) s ystem results in a nonpseudomorphic epilayer with a rather large paral lel strain relative to the Si substrate (epsilon(parallel to) = +1.09% ) is explained, and the model is further used to explain the elastic s train of epitaxial ErSi1.7 and GdSi1.7 rare-earth silicides. (C) 1998 American Vacuum Society.