[en] Crystalline defects in SOS films have been reduced significantly by solid phase epitaxial regrowth after amorphizing the SOS in the vicinity of the silicon-sapphire interface. Amorphization was performed by random implantation of silicon ions. The optimum implantation was chosen to give a projected range of silicon ions and a surface crystalline layer approx. equal to0.8 and 0.2-0.3 times the SOS thickness, respectively. The regrowth proceeds during thermal annealing at more than 600⁰C. Higher temperature annealing leads to a more drastic defect reduction. Dechanneling energy dependence measurements in 250-400 keV ³He ion axial channeling were applied to defect structure analysis as a funtion of depth, and revealed that defect-type changed from twins and/or stacking faults to dislocations and that the dislocation density decreased with depth after the regrowth. (orig.)