Author: Stéphanie Leclerc

Publisher:

Published: 2007

Total Pages: 137

ISBN-13:

In this work, the damage induced by helium implantation in silicon carbide has been studied through XRD and TEM experiments. Combining both XRD experiments and simulations has led us to obtain accurate strain profiles. Implantations have been performed from RT to elevated temperatures to a wide range of fluences. Implantation at RT has been shown to result in a complex picture with mechanisms related to both point defects and helium-vacancy complexes. In particular, helium-vacancy complexes have been seen to strongly influence the strain profile for a concentration of helium exceeding 0.5%. Thresholds for the formation of layers of bubbles and amorphous material have been estimated. This latter depends on the energy of incident ions contrary to what is currently acknowledged. Experiments at elevated temperatures have pointed out two regimes in the damage production as a function of fluence. In the low fluence regime, dynamic annealing occurs in proportion to the defect density over the whole implanted zone. In the high fluence regime, in addition to the dynamic annealing, a migration of interstitial-type defects towards a highly damaged zone has been detected. Both phenomenon lead to a saturation in the near surface strain. Finally, annealing has been performed on the samples implanted at RT. Annealing stages of point defects have been distinguished and related to activation energies. During annealing, strong evolution of the microstructure has been seen to take place in the highly damaged zone. At medium fluences, platelets are formed that collapse into clusters of overpressurized bubbles. These latter induce loop punching which in turn, induces plastic deformation.