GISAXS study of defects in He implanted silicon

The modifications induced in single-crystal silicon by implanted helium have been investigated by grazing incidence small angle X-ray scattering technique. The samples prepared by implanting 2×1016 cm−2 helium ions at 20 keV in silicon wafers held at 77 K were thermally treated for 2 h in the 100–800°C temperature range. It is shown that implantation produced a film with slightly lower density than that of undamaged single crystal silicon. Further thermal treatment caused shrinking of the film leaving well ordered subsurface layer and damaged film below. Upon annealing at 600°C this structure apparently disappear, to be formed again upon annealing at 800°C.