Structural study of YSi1.7 layers formed by channeled ion beam synthesis

Abstract

High quality YSi1.7 layers (χmin of Y is 3.5%) have been formed by 60 keV Y ion implantation in Si (111) substrates to a dose of 1.0×1017/cm2 at 450 °C using channeled ion beam synthesis (CIBS). It shows that, compared to the conventional nonchanneled ion beam synthesis, CIBS is beneficial in forming YSi1.7 layers with better quality due to the lower defect density created in the implanted layer. Rutherford backscattering/channeling and x-ray diffraction have been used to study the structure and the strain of the YSi1.7 layers. The perpendicular and parallel elastic strains of the YSi1.7 epilayer are e⊥ =−0.67%±0.02% and e∥=+1.04%±0.08%. The phenomenon that a nearly zero mismatch of the YSi1.7/Si (111) system results in a nonpseudomorphic epilayer with a rather large parallel strain relative to the Si substrate (ε∥=+1.09%) is explained, and the model is further used to explain the elastic strain of epitaxial ErSi1.7 and GdSi1.7 rare-earth silicides.